diff --git a/TinyFrame/TF_Integration.c b/TinyFrame/TF_Integration.c
index 0b660dc..31d982f 100644
--- a/TinyFrame/TF_Integration.c
+++ b/TinyFrame/TF_Integration.c
@@ -8,6 +8,9 @@
 #include "task_main.h"
 #include "comm/messages.h"
 #include "comm/interfaces.h"
+#include "comm/iface_uart.h"
+#include "comm/iface_nordic.h"
+#include "comm/iface_usb.h"
 #include "framework/system_settings.h"
 
 #include "USB/usbd_cdc_if.h"
@@ -17,76 +20,16 @@
 extern osSemaphoreId semVcomTxReadyHandle;
 extern osMutexId mutTinyFrameTxHandle;
 
-/**
- * USB transmit implementation
- *
- * @param tf - TF
- * @param buff - buffer to send (can be longer than the buffers)
- * @param len - buffer size
- */
-static inline void _USB_WriteImpl(TinyFrame *tf, const uint8_t *buff, uint32_t len)
-{
-#if 1
-    const uint32_t real_size = len;
-
-    // Padding to a multiple of 64 bytes - this is supposed to maximize the bulk transfer speed
-    if ((len&0x3F) && !SystemSettings.visible_vcom) { // this corrupts VCOM on Linux for some reason
-        uint32_t pad = (64 - (len&0x3F));
-        memset((void *) (buff + len), 0, pad);
-        len += pad; // padding to a multiple of 64 (size of the endpoint)
-    }
-
-    // We bypass the USBD driver library's overhead by using the HAL function directly
-    assert_param(HAL_OK == HAL_PCD_EP_Transmit(hUsbDeviceFS.pData, CDC_IN_EP, (uint8_t *) buff, len));
-
-    // The buffer is the TF transmit buffer, we can't leave it to work asynchronously because
-    // the next call could modify it before it's been transmitted (in the case of a chunked / multi-part frame)
-
-    // If this is not the last chunk (assuming all but the last use full 512 bytes of the TF buffer), wait now for completion
-    if (real_size == TF_SENDBUF_LEN) {
-        // TODO this seems wrong - investigate
-        if (pdTRUE != xSemaphoreTake(semVcomTxReadyHandle, 100)) {
-            TF_Error("Tx stalled in WriteImpl");
-            return;
-        }
-    }
-#else
-    (void) tf;
-#define CHUNK 64 // size of the USB packet
-    int32_t total = (int32_t) len;
-    while (total > 0) {
-        const int32_t mxStatus = osSemaphoreWait(semVcomTxReadyHandle, 100);
-        if (mxStatus != osOK) {
-            TF_Error("Tx stalled");
-            return;
-        }
-
-        const uint16_t chunksize = (uint16_t) MIN(total, CHUNK);
-
-        // this is an attempt to speed it up a little by removing a couple levels of indirection
-        assert_param(HAL_OK == HAL_PCD_EP_Transmit(hUsbDeviceFS.pData, CDC_IN_EP, (uint8_t *) buff, chunksize));
-
-//        USBD_LL_Transmit(&hUsbDeviceFS, CDC_IN_EP, (uint8_t *) buff, chunksize);
-//        assert_param(USBD_OK == CDC_Transmit_FS((uint8_t *) buff, chunksize));
-
-        buff += chunksize;
-        total -= chunksize;
-    }
-#endif
-}
-
 void TF_WriteImpl(TinyFrame *tf, const uint8_t *buff, uint32_t len)
 {
     if (gActiveComport == COMPORT_USB) {
-        _USB_WriteImpl(tf, buff, len);
+        iface_usb_transmit(buff, len);
     }
     else if (gActiveComport == COMPORT_USART) {
-        // TODO rewrite this to use DMA, then wait for the DMA
-        for(uint32_t i=0;i<len;i++) {
-            while(!LL_USART_IsActiveFlag_TXE(USART2));
-            LL_USART_TransmitData8(USART2, buff[i]);
-        }
-        xSemaphoreGive(semVcomTxReadyHandle); // act as if we just finished it and this is perhaps the DMA irq
+        iface_uart_transmit(buff, len);
+    }
+    else if (gActiveComport == COMPORT_NORDIC) {
+        iface_nordic_transmit(buff, len);
     }
     else {
         // TODO other transports
@@ -104,7 +47,7 @@ bool TF_ClaimTx(TinyFrame *tf)
 
     // The last chunk from some previous frame may still be being transmitted,
     // wait for it to finish (the semaphore is given in the CDC tx done handler)
-    if (pdTRUE != xSemaphoreTake(semVcomTxReadyHandle, 100)) {
+    if (pdTRUE != xSemaphoreTake(semVcomTxReadyHandle, 200)) {
         TF_Error("Tx stalled in Claim");
 
         // release the guarding mutex again
diff --git a/comm/iface_nordic.c b/comm/iface_nordic.c
new file mode 100644
index 0000000..3bef6bf
--- /dev/null
+++ b/comm/iface_nordic.c
@@ -0,0 +1,175 @@
+//
+// Created by MightyPork on 2018/04/06.
+//
+
+#include "iface_nordic.h"
+#include "nrf_pins.h"
+#include "resources.h"
+#include "hw_utils.h"
+#include "nrf.h"
+#include "unit_base.h"
+#include "system_settings.h"
+#include "utils/hexdump.h"
+
+extern osSemaphoreId semVcomTxReadyHandle;
+
+#define RX_PIPE_NUM 0
+
+void iface_nordic_claim_resources(void)
+{
+    assert_param(E_SUCCESS == rsc_claim(&UNIT_SYSTEM, NRF_R_SPI));
+    assert_param(E_SUCCESS == rsc_claim(&UNIT_SYSTEM, NRF_R_CE));
+    assert_param(E_SUCCESS == rsc_claim(&UNIT_SYSTEM, NRF_R_NSS));
+    assert_param(E_SUCCESS == rsc_claim(&UNIT_SYSTEM, NRF_R_IRQ));
+    assert_param(E_SUCCESS == rsc_claim(&UNIT_SYSTEM, NRF_R_MISO));
+    assert_param(E_SUCCESS == rsc_claim(&UNIT_SYSTEM, NRF_R_MOSI));
+    assert_param(E_SUCCESS == rsc_claim(&UNIT_SYSTEM, NRF_R_SCK));
+
+    assert_param(E_SUCCESS == rsc_claim(&UNIT_SYSTEM, R_EXTI0+NRF_EXTI_LINENUM));
+}
+
+void iface_nordic_free_resources(void)
+{
+    rsc_free(&UNIT_SYSTEM, NRF_R_SPI);
+    rsc_free(&UNIT_SYSTEM, NRF_R_CE);
+    rsc_free(&UNIT_SYSTEM, NRF_R_NSS);
+    rsc_free(&UNIT_SYSTEM, NRF_R_IRQ);
+    rsc_free(&UNIT_SYSTEM, NRF_R_MISO);
+    rsc_free(&UNIT_SYSTEM, NRF_R_MOSI);
+    rsc_free(&UNIT_SYSTEM, NRF_R_SCK);
+
+    rsc_free(&UNIT_SYSTEM, R_EXTI0+NRF_EXTI_LINENUM);
+}
+
+static uint8_t rx_buffer[32];
+
+static void NrfIrqHandler(void *arg)
+{
+    LL_EXTI_ClearFlag_0_31(LL_EXTI_LINES[NRF_EXTI_LINENUM]);
+    dbg_nrf("[EXTI] ---");
+
+    while (NRF_IsRxPacket()) {
+        uint8_t pipenum;
+        uint8_t count = NRF_ReceivePacket(rx_buffer, &pipenum);
+        if (count > 0) {
+            dbg_nrf("NRF RX %d bytes", (int) count);
+            rxQuePostMsg(rx_buffer, count);
+        }
+        else {
+            dbg("IRQ but no Rx");
+        }
+    }
+
+    dbg_nrf("--- end [EXTI]");
+}
+
+bool iface_nordic_init(void)
+{
+    dbg("Setting up Nordic...");
+
+    hw_periph_clock_enable(NRF_SPI);
+
+    // SPI pins
+    assert_param(E_SUCCESS == hw_configure_gpiorsc_af(NRF_R_SCK, NRF_SPI_AF));
+    assert_param(E_SUCCESS == hw_configure_gpiorsc_af(NRF_R_MOSI, NRF_SPI_AF));
+    assert_param(E_SUCCESS == hw_configure_gpiorsc_af(NRF_R_MISO, NRF_SPI_AF));
+
+    // Manual pins
+    LL_GPIO_SetPinMode(NRF_NSS_GPIO_Port, NRF_NSS_Pin, LL_GPIO_MODE_OUTPUT);
+    LL_GPIO_SetPinMode(NRF_CE_GPIO_Port, NRF_CE_Pin, LL_GPIO_MODE_OUTPUT);
+    LL_GPIO_SetPinMode(NRF_IRQ_GPIO_Port, NRF_IRQ_Pin, LL_GPIO_MODE_INPUT);
+
+    LL_SPI_Disable(NRF_SPI);
+    {
+        LL_SPI_SetBaudRatePrescaler(NRF_SPI, LL_SPI_BAUDRATEPRESCALER_DIV32);
+        //LL_SPI_BAUDRATEPRESCALER_DIV8
+
+        LL_SPI_SetClockPolarity(NRF_SPI,     LL_SPI_POLARITY_LOW);
+        LL_SPI_SetClockPhase(NRF_SPI,        LL_SPI_PHASE_1EDGE);
+        LL_SPI_SetTransferDirection(NRF_SPI, LL_SPI_FULL_DUPLEX);
+        LL_SPI_SetTransferBitOrder(NRF_SPI,  LL_SPI_MSB_FIRST);
+
+        LL_SPI_SetNSSMode(NRF_SPI, LL_SPI_NSS_SOFT);
+        LL_SPI_SetDataWidth(NRF_SPI, LL_SPI_DATAWIDTH_8BIT);
+        LL_SPI_SetRxFIFOThreshold(NRF_SPI, LL_SPI_RX_FIFO_TH_QUARTER); // trigger RXNE on 1 byte
+
+        LL_SPI_SetMode(NRF_SPI, LL_SPI_MODE_MASTER);
+    }
+    LL_SPI_Enable(NRF_SPI);
+
+
+    dbg("configure nrf module");
+
+    // Now configure the radio
+    NRF_Init(NRF_SPEED_2M); // TODO configurable speed
+    NRF_SetChannel(SystemSettings.nrf_channel);
+    NRF_SetBaseAddress(SystemSettings.nrf_network);
+    NRF_SetRxAddress(RX_PIPE_NUM, SystemSettings.nrf_address);
+    NRF_EnablePipe(RX_PIPE_NUM);
+    NRF_ModeRX();
+
+    dbg("enable exti");
+    // EXTI
+    LL_EXTI_EnableIT_0_31(LL_EXTI_LINES[NRF_EXTI_LINENUM]);
+    LL_EXTI_EnableFallingTrig_0_31(LL_EXTI_LINES[NRF_EXTI_LINENUM]);
+    LL_SYSCFG_SetEXTISource(NRF_SYSCFG_EXTI_PORT, LL_SYSCFG_EXTI_LINES[NRF_EXTI_LINENUM]);
+    irqd_attach(EXTIS[NRF_EXTI_LINENUM], NrfIrqHandler, NULL);
+    // TODO increase priority in NVIC?
+
+    dbg("nrf setup done");
+    return true;
+}
+
+void iface_nordic_deinit(void)
+{
+    LL_EXTI_DisableIT_0_31(LL_EXTI_LINES[NRF_EXTI_LINENUM]);
+    LL_EXTI_DisableFallingTrig_0_31(LL_EXTI_LINES[NRF_EXTI_LINENUM]);
+    irqd_detach(EXTIS[NRF_EXTI_LINENUM], NrfIrqHandler);
+    hw_periph_clock_disable(NRF_SPI);
+
+    hw_deinit_pin_rsc(NRF_R_SCK);
+    hw_deinit_pin_rsc(NRF_R_MOSI);
+    hw_deinit_pin_rsc(NRF_R_MISO);
+    hw_deinit_pin_rsc(NRF_R_NSS);
+    hw_deinit_pin_rsc(NRF_R_CE);
+    hw_deinit_pin_rsc(NRF_R_IRQ);
+}
+
+// FIXME
+#define MAX_RETRY 5
+
+void iface_nordic_transmit(const uint8_t *buff, uint32_t len)
+{
+    bool suc = false;
+    while (len > 0) {
+        uint8_t chunk = (uint8_t) MIN(32, len);
+
+        uint16_t delay = 1;
+        //hexDump("Tx chunk", buff, chunk);
+        for (int i = 0; i < MAX_RETRY; i++) {
+            suc = NRF_SendPacket(RX_PIPE_NUM, buff, chunk); // use the pipe to retrieve the address
+            if (!suc) {
+                vTaskDelay(delay);
+                delay *= 2; // longer delay next time
+            } else {
+                break;
+            }
+        }
+
+        if (!suc) {
+            break;
+        }
+
+        buff += chunk;
+        len -= chunk;
+    }
+
+    if (suc) {
+        dbg_nrf("+ NRF Tx OK!");
+    } else {
+        dbg("- NRF sending failed");
+    }
+
+    // give when it's done
+    xSemaphoreGive(semVcomTxReadyHandle); // similar to how it's done in USB - this is called in the Tx Done handler
+}
diff --git a/comm/iface_nordic.h b/comm/iface_nordic.h
new file mode 100644
index 0000000..c07d739
--- /dev/null
+++ b/comm/iface_nordic.h
@@ -0,0 +1,20 @@
+//
+// Created by MightyPork on 2018/04/06.
+//
+
+#ifndef GEX_F072_IFACE_NORDIC_H
+#define GEX_F072_IFACE_NORDIC_H
+
+#include "platform.h"
+
+void iface_nordic_claim_resources(void);
+
+void iface_nordic_free_resources(void);
+
+void iface_nordic_deinit(void);
+
+bool iface_nordic_init(void);
+
+void iface_nordic_transmit(const uint8_t *buff, uint32_t len);
+
+#endif //GEX_F072_IFACE_NORDIC_H
diff --git a/comm/iface_uart.c b/comm/iface_uart.c
new file mode 100644
index 0000000..0d4393e
--- /dev/null
+++ b/comm/iface_uart.c
@@ -0,0 +1,105 @@
+//
+// Created by MightyPork on 2018/04/06.
+//
+
+#include "platform.h"
+#include "iface_uart.h"
+#include "resources.h"
+#include "hw_utils.h"
+#include "irq_dispatcher.h"
+#include "task_msg.h"
+#include "system_settings.h"
+
+extern osSemaphoreId semVcomTxReadyHandle;
+
+static uint32_t usart_rxi = 0;
+static uint8_t usart_rx_buffer[MSG_QUE_SLOT_SIZE];
+static uint32_t last_rx_time = 0;
+
+void iface_uart_claim_resources(void)
+{
+    assert_param(E_SUCCESS == rsc_claim(&UNIT_SYSTEM, R_USART2));
+    assert_param(E_SUCCESS == rsc_claim(&UNIT_SYSTEM, R_PA2));
+    assert_param(E_SUCCESS == rsc_claim(&UNIT_SYSTEM, R_PA3));
+}
+
+void iface_uart_free_resources(void)
+{
+    rsc_free(&UNIT_SYSTEM, R_USART2);
+    rsc_free(&UNIT_SYSTEM, R_PA2);
+    rsc_free(&UNIT_SYSTEM, R_PA3);
+}
+
+/** Handler for the USART transport */
+static void com_UsartIrqHandler(void *arg)
+{
+    (void)arg;
+    if (LL_USART_IsActiveFlag_RXNE(USART2)) {
+        vPortEnterCritical();
+        {
+            usart_rx_buffer[usart_rxi++] = LL_USART_ReceiveData8(USART2);
+            if (usart_rxi == MSG_QUE_SLOT_SIZE) {
+                rxQuePostMsg(usart_rx_buffer, MSG_QUE_SLOT_SIZE); // avoid it happening in the irq
+                usart_rxi = 0;
+            }
+            last_rx_time = HAL_GetTick();
+        }
+        vPortExitCritical();
+    }
+}
+
+/** this is called from the hal tick irq */
+void com_iface_flush_buffer(void)
+{
+    if (usart_rxi > 0 && (HAL_GetTick()-last_rx_time)>=2) {
+        vPortEnterCritical();
+        {
+            rxQuePostMsg(usart_rx_buffer, usart_rxi);
+            usart_rxi = 0;
+        }
+        vPortExitCritical();
+    }
+}
+
+bool iface_uart_init(void)
+{
+    dbg("Setting up UART transfer");
+    assert_param(E_SUCCESS == hw_configure_gpiorsc_af(R_PA2, LL_GPIO_AF_1));
+    assert_param(E_SUCCESS == hw_configure_gpiorsc_af(R_PA3, LL_GPIO_AF_1));
+
+    __HAL_RCC_USART2_CLK_ENABLE();
+    __HAL_RCC_USART2_FORCE_RESET();
+    __HAL_RCC_USART2_RELEASE_RESET();
+
+    LL_USART_Disable(USART2);
+
+    LL_USART_SetBaudRate(USART2, PLAT_APB1_HZ, LL_USART_OVERSAMPLING_16, SystemSettings.comm_uart_baud);
+    dbg("baud = %d", (int)SystemSettings.comm_uart_baud);
+
+    irqd_attach(USART2, com_UsartIrqHandler, NULL);
+    LL_USART_EnableIT_RXNE(USART2);
+    LL_USART_SetTransferDirection(USART2, LL_USART_DIRECTION_TX_RX);
+
+    LL_USART_Enable(USART2);
+
+    return true; // always OK (TODO check voltage on Rx if it's 3V3 when idle?)
+}
+
+void iface_uart_deinit(void)
+{
+    // this doesn't normally happen
+    hw_deinit_pin_rsc(R_PA2);
+    hw_deinit_pin_rsc(R_PA3);
+    __HAL_RCC_USART2_CLK_DISABLE();
+    irqd_detach(USART2, com_UsartIrqHandler);
+}
+
+void iface_uart_transmit(const uint8_t *buff, uint32_t len)
+{
+    // TODO rewrite this to use DMA, then wait for the DMA
+    for(uint32_t i=0;i<len;i++) {
+        while(!LL_USART_IsActiveFlag_TXE(USART2));
+        LL_USART_TransmitData8(USART2, buff[i]);
+    }
+    xSemaphoreGive(semVcomTxReadyHandle); // act as if we just finished it and this is perhaps the DMA irq
+}
diff --git a/comm/iface_uart.h b/comm/iface_uart.h
new file mode 100644
index 0000000..71b6c3f
--- /dev/null
+++ b/comm/iface_uart.h
@@ -0,0 +1,20 @@
+//
+// Created by MightyPork on 2018/04/06.
+//
+
+#ifndef GEX_F072_IFACE_UART_H
+#define GEX_F072_IFACE_UART_H
+
+#include "platform.h"
+
+void com_iface_flush_buffer(void);
+
+void iface_uart_deinit(void);
+bool iface_uart_init(void);
+
+void iface_uart_free_resources(void);
+void iface_uart_claim_resources(void);
+
+void iface_uart_transmit(const uint8_t *buff, uint32_t len);
+
+#endif //GEX_F072_IFACE_UART_H
diff --git a/comm/iface_usb.c b/comm/iface_usb.c
new file mode 100644
index 0000000..e75c40a
--- /dev/null
+++ b/comm/iface_usb.c
@@ -0,0 +1,73 @@
+//
+// Created by MightyPork on 2018/04/06.
+//
+
+#include "iface_usb.h"
+#include "TinyFrame.h"
+#include "system_settings.h"
+#include "USB/usb_device.h"
+
+extern osSemaphoreId semVcomTxReadyHandle;
+extern osMutexId mutTinyFrameTxHandle;
+
+bool iface_usb_ready(void)
+{
+    return 0 != (USB->DADDR & USB_DADDR_ADD);
+}
+
+/**
+ * USB transmit implementation
+ *
+ * @param buff - buffer to send (can be longer than the buffers)
+ * @param len - buffer size
+ */
+void iface_usb_transmit(const uint8_t *buff, uint32_t len)
+{
+#if 1
+    const uint32_t real_size = len;
+
+    // Padding to a multiple of 64 bytes - this is supposed to maximize the bulk transfer speed
+    if ((len&0x3F) && !SystemSettings.visible_vcom) { // this corrupts VCOM on Linux for some reason
+        uint32_t pad = (64 - (len&0x3F));
+        memset((void *) (buff + len), 0, pad);
+        len += pad; // padding to a multiple of 64 (size of the endpoint)
+    }
+
+    // We bypass the USBD driver library's overhead by using the HAL function directly
+    assert_param(HAL_OK == HAL_PCD_EP_Transmit(hUsbDeviceFS.pData, CDC_IN_EP, (uint8_t *) buff, len));
+
+    // The buffer is the TF transmit buffer, we can't leave it to work asynchronously because
+    // the next call could modify it before it's been transmitted (in the case of a chunked / multi-part frame)
+
+    // If this is not the last chunk (assuming all but the last use full 512 bytes of the TF buffer), wait now for completion
+    if (real_size == TF_SENDBUF_LEN) {
+        // TODO this seems wrong - investigate
+        if (pdTRUE != xSemaphoreTake(semVcomTxReadyHandle, 100)) {
+            TF_Error("Tx stalled in WriteImpl");
+            return;
+        }
+    }
+#else
+    (void) tf;
+#define CHUNK 64 // size of the USB packet
+    int32_t total = (int32_t) len;
+    while (total > 0) {
+        const int32_t mxStatus = osSemaphoreWait(semVcomTxReadyHandle, 100);
+        if (mxStatus != osOK) {
+            TF_Error("Tx stalled");
+            return;
+        }
+
+        const uint16_t chunksize = (uint16_t) MIN(total, CHUNK);
+
+        // this is an attempt to speed it up a little by removing a couple levels of indirection
+        assert_param(HAL_OK == HAL_PCD_EP_Transmit(hUsbDeviceFS.pData, CDC_IN_EP, (uint8_t *) buff, chunksize));
+
+//        USBD_LL_Transmit(&hUsbDeviceFS, CDC_IN_EP, (uint8_t *) buff, chunksize);
+//        assert_param(USBD_OK == CDC_Transmit_FS((uint8_t *) buff, chunksize));
+
+        buff += chunksize;
+        total -= chunksize;
+    }
+#endif
+}
diff --git a/comm/iface_usb.h b/comm/iface_usb.h
new file mode 100644
index 0000000..d83f370
--- /dev/null
+++ b/comm/iface_usb.h
@@ -0,0 +1,20 @@
+//
+// Created by MightyPork on 2018/04/06.
+//
+
+#ifndef GEX_F072_IFACE_USB_H
+#define GEX_F072_IFACE_USB_H
+
+#include "platform.h"
+
+bool iface_usb_ready(void);
+
+/**
+ * USB transmit implementation
+ *
+ * @param buff - buffer to send (can be longer than the buffers)
+ * @param len - buffer size
+ */
+void iface_usb_transmit(const uint8_t *buff, uint32_t len);
+
+#endif //GEX_F072_IFACE_USB_H
diff --git a/comm/interfaces.c b/comm/interfaces.c
index 13086ec..0ab281c 100644
--- a/comm/interfaces.c
+++ b/comm/interfaces.c
@@ -2,7 +2,6 @@
 // Created by MightyPork on 2018/03/23.
 //
 
-#include <stm32f072xb.h>
 #include "platform.h"
 #include "usbd_core.h"
 #include "USB/usb_device.h"
@@ -12,13 +11,26 @@
 #include "framework/resources.h"
 #include "platform/hw_utils.h"
 #include "framework/unit_base.h"
+#include "nrf_pins.h"
+#include "iface_uart.h"
+#include "iface_usb.h"
+#include "iface_nordic.h"
+
+const char * COMPORT_NAMES[] = {
+    "NONE",
+    "USB",
+    "UART",
+    "NRF",
+    "LORA",
+};
+
 
 enum ComportSelection gActiveComport = COMPORT_USB; // start with USB so the handlers work correctly initially
 
 static uint32_t last_switch_time = 0; // started with USB
 static bool xfer_verify_done = false;
 
-static void configure_interface(enum ComportSelection iface);
+static bool configure_interface(enum ComportSelection iface);
 
 /** Switch com transfer if the current one doesnt seem to work */
 void com_switch_transfer_if_needed(void)
@@ -30,30 +42,36 @@ void com_switch_transfer_if_needed(void)
 
     if (gActiveComport == COMPORT_USB) {
         if (elapsed > 1000) {
-            // USB may or may not work, depending on whether the module is plugged -
-            // in or running from a battery/external supply remotely.
+            // USB may or may not work, depending on whether the module is plugged in
+            // or running from a battery/external supply remotely.
 
             // Check if USB is enumerated
 
-            const uint32_t uadr = (USB->DADDR & USB_DADDR_ADD);
-            if (0 == uadr) {
+            if (!iface_usb_ready()) {
                 dbg("Not enumerated, assuming USB is dead");
 
-                // Fallback to bare USART
-                if (SystemSettings.use_comm_uart) {
-                    configure_interface(COMPORT_USART);
-                }
-                else if (SystemSettings.use_comm_nordic) {
-                    configure_interface(COMPORT_NORDIC); // this fallbacks to LoRa if LoRa enabled
-                }
-                else if (SystemSettings.use_comm_lora) {
-                    configure_interface(COMPORT_LORA);
-                }
-                else {
-                    dbg("No alternate com interface configured, leaving USB enabled.");
-                }
+                // Fallback to radio or bare USART
+                do {
+                    if (SystemSettings.use_comm_nordic) {
+                        if (configure_interface(COMPORT_NORDIC)) break;
+                    }
+
+#if 0
+                    if (SystemSettings.use_comm_lora) {
+                        if (configure_interface(COMPORT_LORA)) break;
+                    }
+#endif
+
+                    if (SystemSettings.use_comm_uart) {
+                        // after nordic/lora
+                        if (configure_interface(COMPORT_USART)) break;
+                    }
+
+                    dbg("No alternate com interface configured.");
+                    gActiveComport = COMPORT_NONE;
+                } while (0);
             } else {
-                dbg("USB got address 0x%02x - OK", (int)uadr);
+                dbg("USB got address - OK");
             }
 
             xfer_verify_done = true;
@@ -65,24 +83,11 @@ void com_switch_transfer_if_needed(void)
 void com_claim_resources_for_alt_transfers(void)
 {
     if (SystemSettings.use_comm_uart) {
-        do {
-            if (E_SUCCESS != rsc_claim(&UNIT_SYSTEM, R_USART2)) {
-                SystemSettings.use_comm_uart = false;
-                break;
-            }
+        iface_uart_claim_resources();
+    }
 
-            if (E_SUCCESS != rsc_claim(&UNIT_SYSTEM, R_PA2)) {
-                SystemSettings.use_comm_uart = false;
-                rsc_free(&UNIT_SYSTEM, R_USART2);
-                break;
-            }
-            if (E_SUCCESS != rsc_claim(&UNIT_SYSTEM, R_PA3)) {
-                SystemSettings.use_comm_uart = false;
-                rsc_free(&UNIT_SYSTEM, R_USART2);
-                rsc_free(&UNIT_SYSTEM, R_PA2);
-                break;
-            }
-        } while (0);
+    if (SystemSettings.use_comm_nordic) {
+        iface_nordic_claim_resources();
     }
 }
 
@@ -90,48 +95,16 @@ void com_claim_resources_for_alt_transfers(void)
 void com_release_resources_for_alt_transfers(void)
 {
     if (SystemSettings.use_comm_uart) {
-        rsc_free(&UNIT_SYSTEM, R_USART2);
-        rsc_free(&UNIT_SYSTEM, R_PA2);
-        rsc_free(&UNIT_SYSTEM, R_PA3);
+        iface_uart_free_resources();
     }
-}
-
-static uint32_t usart_rxi = 0;
-static uint8_t usart_rx_buffer[MSG_QUE_SLOT_SIZE];
-static uint32_t last_rx_time = 0;
 
-/** Handler for the USART transport */
-static void com_UsartIrqHandler(void *arg)
-{
-    (void)arg;
-    if (LL_USART_IsActiveFlag_RXNE(USART2)) {
-        vPortEnterCritical();
-        {
-            usart_rx_buffer[usart_rxi++] = LL_USART_ReceiveData8(USART2);
-            if (usart_rxi == MSG_QUE_SLOT_SIZE) {
-                rxQuePostMsg(usart_rx_buffer, MSG_QUE_SLOT_SIZE); // avoid it happening in the irq
-                usart_rxi = 0;
-            }
-            last_rx_time = HAL_GetTick();
-        }
-        vPortExitCritical();
+    if (SystemSettings.use_comm_nordic) {
+        iface_nordic_free_resources();
     }
 }
 
-/** this is called from the hal tick irq */
-void com_iface_flush_buffer(void)
-{
-    if (usart_rxi > 0 && (HAL_GetTick()-last_rx_time)>=2) {
-        vPortEnterCritical();
-        {
-            rxQuePostMsg(usart_rx_buffer, usart_rxi);
-            usart_rxi = 0;
-        }
-        vPortExitCritical();
-    }
-}
 
-static void configure_interface(enum ComportSelection iface)
+static bool configure_interface(enum ComportSelection iface)
 {
     // Teardown
     if (gActiveComport == COMPORT_USB) {
@@ -140,68 +113,36 @@ static void configure_interface(enum ComportSelection iface)
         __HAL_RCC_USB_CLK_DISABLE();
     }
     else if (gActiveComport == COMPORT_USART) {
-        // this doesn't normally happen
-        hw_deinit_pin_rsc(R_PA2);
-        hw_deinit_pin_rsc(R_PA3);
-        __HAL_RCC_USART2_CLK_DISABLE();
-        irqd_detach(USART2, com_UsartIrqHandler);
+        iface_uart_deinit();
     }
-    gActiveComport = COMPORT_NONE;
+    else if (gActiveComport == COMPORT_NORDIC) {
+        iface_nordic_deinit();
+    }
+
+
+    gActiveComport = iface;
 
     // Init
     if (iface == COMPORT_USB) {
         trap("illegal"); // this never happens
+        return false;
     }
     else if (iface == COMPORT_USART) {
-        dbg("Setting up UART transfer");
-        assert_param(E_SUCCESS == hw_configure_gpiorsc_af(R_PA2, LL_GPIO_AF_1));
-        assert_param(E_SUCCESS == hw_configure_gpiorsc_af(R_PA3, LL_GPIO_AF_1));
-
-        __HAL_RCC_USART2_CLK_ENABLE();
-        __HAL_RCC_USART2_FORCE_RESET();
-        __HAL_RCC_USART2_RELEASE_RESET();
-
-        LL_USART_Disable(USART2);
-
-        LL_USART_SetBaudRate(USART2, PLAT_APB1_HZ, LL_USART_OVERSAMPLING_16, SystemSettings.comm_uart_baud);
-        dbg("baud = %d", (int)SystemSettings.comm_uart_baud);
-
-        irqd_attach(USART2, com_UsartIrqHandler, NULL);
-        LL_USART_EnableIT_RXNE(USART2);
-        LL_USART_SetTransferDirection(USART2, LL_USART_DIRECTION_TX_RX);
-
-        LL_USART_Enable(USART2);
+        return iface_uart_init();
     }
-    else {
-        if (iface == COMPORT_NORDIC) {
-            // Try to configure nordic
-            dbg("Setting up nRF transfer");
-
-            // TODO set up and check nRF transport
-
-            // On failure, try setting up LoRa
-            dbg("nRF failed to init");
-            if (SystemSettings.use_comm_lora) {
-                iface = COMPORT_LORA;
-            } else {
-                iface = COMPORT_NONE; // fail
-            }
-        }
-
-        if (iface == COMPORT_LORA) {
-            // Try to configure nordic
-            dbg("Setting up LoRa transfer");
-
-            // TODO set up and check LoRa transport
-
-            dbg("LoRa failed to init");
-            iface = COMPORT_NONE; // fail
-        }
+    else if (iface == COMPORT_NORDIC) {
+        return iface_nordic_init();
     }
-
-    if (iface == COMPORT_NONE) {
-        dbg("NO COM PORT AVAILABLE!");
+#if 0
+    else if (iface == COMPORT_LORA) {
+        // Try to configure nordic
+        dbg("Setting up LoRa transfer");
+        // TODO set up and check LoRa transport
+        dbg("LoRa not impl!");
+        return false;
+    }
+#endif
+    else {
+        trap("Bad iface %d", iface);
     }
-
-    gActiveComport = iface;
 }
diff --git a/comm/interfaces.h b/comm/interfaces.h
index 5d65766..fe56abe 100644
--- a/comm/interfaces.h
+++ b/comm/interfaces.h
@@ -15,6 +15,8 @@ enum ComportSelection {
     COMPORT_LORA = 4,
 };
 
+extern const char * COMPORT_NAMES[];
+
 /**
  * The currently active communication port
  */
diff --git a/comm/messages.c b/comm/messages.c
index e1b679a..170d8b9 100644
--- a/comm/messages.c
+++ b/comm/messages.c
@@ -11,6 +11,7 @@
 #include "framework/system_settings.h"
 #include "utils/malloc_safe.h"
 #include "platform/status_led.h"
+#include "interfaces.h"
 
 static TinyFrame tf_;
 TinyFrame *comm = &tf_;
@@ -23,7 +24,7 @@ TinyFrame *comm = &tf_;
 static TF_Result lst_ping(TinyFrame *tf, TF_Msg *msg)
 {
     com_respond_snprintf(msg->frame_id, MSG_SUCCESS,
-                         "GEX v%s on %s", GEX_VERSION, GEX_PLATFORM);
+                         "GEX v%s on %s (%s)", GEX_VERSION, GEX_PLATFORM, COMPORT_NAMES[gActiveComport]);
     return TF_STAY;
 }
 
@@ -58,26 +59,33 @@ static TF_Result lst_list_units(TinyFrame *tf, TF_Msg *msg)
 
 // ---------------------------------------------------------------------------
 
-/** Callback for bulk read of the settings file */
-static void settings_bulkread_cb(BulkRead *bulk, uint32_t chunk, uint8_t *buffer)
+/** Callback for bulk read of a settings file */
+static void ini_bulkread_cb(BulkRead *bulk, uint32_t chunk, uint8_t *buffer)
 {
     // clean-up request
     if (buffer == NULL) {
         free_ck(bulk);
         iw_end();
-//        dbg("INI read complete.");
         return;
     }
 
     if (bulk->offset == 0) iw_begin();
 
     IniWriter iw = iw_init((char *)buffer, bulk->offset, chunk);
-    iw.tag = 1;
-    settings_build_units_ini(&iw);
+    iw.tag = 1; // indicates this is read via the API (affects some comments)
+
+    uint8_t filenum = (uint8_t) (int) bulk->userdata;
+    
+    if (filenum == 0) {
+        settings_build_units_ini(&iw);
+    }
+    else if (filenum == 1) {
+        settings_build_system_ini(&iw);
+    }
 }
 
 /**
- * Listener: Export INI file via TF
+ * Listener: Export a file via TF
  */
 static TF_Result lst_ini_export(TinyFrame *tf, TF_Msg *msg)
 {
@@ -86,14 +94,29 @@ static TF_Result lst_ini_export(TinyFrame *tf, TF_Msg *msg)
     BulkRead *bulk = malloc_ck(sizeof(BulkRead));
     assert_param(bulk != NULL);
 
+    uint8_t filenum = 0;
+
+    // if any payload, the first byte defines the file to read
+    // 0 - units
+    // 1 - system
+    // (this is optional for backwards compatibility)
+    if (msg->len > 0) {
+        filenum = msg->data[0];
+    }
+
     bulk->frame_id = msg->frame_id;
-    bulk->len = iw_measure_total(settings_build_units_ini, 1);
-    bulk->read = settings_bulkread_cb;
-    bulk->userdata = NULL;
+    bulk->read = ini_bulkread_cb;
+    bulk->userdata = (void *) (int)filenum;
+
+    if (filenum == 0) {
+        bulk->len = iw_measure_total(settings_build_units_ini, 1);
+    }
+    else if (filenum == 1) {
+        bulk->len = iw_measure_total(settings_build_system_ini, 1);
+    }
 
     bulkread_start(tf, bulk);
     Indicator_Effect(STATUS_DISK_BUSY_SHORT);
-
     return TF_STAY;
 }
 
@@ -142,7 +165,7 @@ static TF_Result lst_ini_import(TinyFrame *tf, TF_Msg *msg)
     PayloadParser pp = pp_start(msg->data, msg->len, NULL);
     uint32_t len = pp_u32(&pp);
     if (!pp.ok) {
-        com_respond_error(msg->frame_id, E_PROTOCOL_BREACH);
+        com_respond_error(msg->frame_id, E_MALFORMED_COMMAND);
         goto done;
     }
 
@@ -151,11 +174,8 @@ static TF_Result lst_ini_import(TinyFrame *tf, TF_Msg *msg)
 
     settings_load_ini_begin();
     ini_parse_begin(iniparser_cb, NULL);
-
     bulkwrite_start(tf, bulk);
-
     Indicator_Effect(STATUS_DISK_BUSY);
-
 done:
     return TF_STAY;
 }
diff --git a/comm/nrf.c b/comm/nrf.c
new file mode 100644
index 0000000..45670e2
--- /dev/null
+++ b/comm/nrf.c
@@ -0,0 +1,530 @@
+//
+// Created by MightyPork on 2018/04/02.
+//
+
+#include "platform.h"
+#include "nrf.h"
+
+/**
+ * Read a register
+ *
+ * @param reg - register number (max 83)
+ * @return register value
+ */
+static uint8_t NRF_ReadRegister(uint8_t reg);
+
+/**
+ * Write a register
+ *
+ * @param reg - register number (max 83)
+ * @param value - register value
+ * @return status register value
+ */
+static uint8_t NRF_WriteRegister(uint8_t reg, uint8_t value);
+
+// Internal use
+static uint8_t NRF_WriteBuffer(uint8_t reg, const uint8_t *pBuf, uint8_t bytes);
+
+static uint8_t NRF_ReadBuffer(uint8_t reg, uint8_t *pBuf, uint8_t bytes);
+
+/**
+ * Set TX address for next frame
+ *
+ * @param SendTo - addr
+ */
+static void NRF_SetTxAddress(uint8_t ToAddr);
+
+//----------------------------------------------------------
+
+/** Tight asm loop */
+#define __asm_loop(cycles) \
+do { \
+    register uint32_t _count asm ("r4") = cycles; \
+    asm volatile( \
+        ".syntax unified\n" \
+        ".thumb\n" \
+        "0:" \
+            "subs %0, #1\n" \
+            "bne 0b\n" \
+        : "+r" (_count)); \
+} while(0)
+
+// 12 for 72 MHz
+#define _delay_us(n) __asm_loop((n)*8)
+
+static inline void CE(bool level) {
+    __asm_loop(1);
+    if (level) LL_GPIO_SetOutputPin(NRF_CE_GPIO_Port, NRF_CE_Pin);
+    else LL_GPIO_ResetOutputPin(NRF_CE_GPIO_Port, NRF_CE_Pin);
+    __asm_loop(1);
+}
+
+static inline void NSS(bool level) {
+    __asm_loop(1);
+    if (level) LL_GPIO_SetOutputPin(NRF_NSS_GPIO_Port, NRF_NSS_Pin);
+    else LL_GPIO_ResetOutputPin(NRF_NSS_GPIO_Port, NRF_NSS_Pin);
+    __asm_loop(1);
+}
+
+static uint8_t spi(uint8_t tx) {
+    while (! LL_SPI_IsActiveFlag_TXE(NRF_SPI));
+    LL_SPI_TransmitData8(NRF_SPI, tx);
+    while (! LL_SPI_IsActiveFlag_RXNE(NRF_SPI));
+    return LL_SPI_ReceiveData8(NRF_SPI);
+}
+
+//-------
+
+/*
+ * from: http://barefootelectronics.com/NRF24L01.aspx
+ */
+
+#define CMD_READ_REG        0x00  // Read command to register
+#define CMD_WRITE_REG       0x20  // Write command to register
+#define CMD_RD_RX_PLD     0x61  // Read RX payload register address
+#define CMD_WR_TX_PLD     0xA0  // Write TX payload register address
+#define CMD_FLUSH_TX        0xE1  // Flush TX register command
+#define CMD_FLUSH_RX        0xE2  // Flush RX register command
+#define CMD_REUSE_TX_PL     0xE3  // Reuse TX payload register command
+#define CMD_RD_RX_PL_WIDTH    0x60  // Read RX Payload Width
+#define CMD_WR_ACK_PLD   0xA8  // Write ACK payload for Pipe (Add pipe number 0-6)
+#define CMD_WR_TX_PLD_NK  0xB0  // Write ACK payload for not ack
+#define CMD_NOP             0xFF  // No Operation, might be used to read status register
+
+// SPI(nRF24L01) registers(addresses)
+#define RG_CONFIG          0x00  // 'Config' register address
+#define RG_EN_AA           0x01  // 'Enable Auto Acknowledgment' register address
+#define RG_EN_RXADDR       0x02  // 'Enabled RX addresses' register address
+#define RG_SETUP_AW        0x03  // 'Setup address width' register address
+#define RG_SETUP_RETR      0x04  // 'Setup Auto. Retrans' register address
+#define RG_RF_CH           0x05  // 'RF channel' register address
+#define RG_RF_SETUP        0x06  // 'RF setup' register address
+#define RG_STATUS          0x07  // 'Status' register address
+#define RG_OBSERVE_TX      0x08  // 'Observe TX' register address
+#define RG_CD              0x09  // 'Carrier Detect' register address
+#define RG_RX_ADDR_P0      0x0A  // 'RX address pipe0' register address
+#define RG_RX_ADDR_P1      0x0B  // 'RX address pipe1' register address
+#define RG_RX_ADDR_P2      0x0C  // 'RX address pipe2' register address
+#define RG_RX_ADDR_P3      0x0D  // 'RX address pipe3' register address
+#define RG_RX_ADDR_P4      0x0E  // 'RX address pipe4' register address
+#define RG_RX_ADDR_P5      0x0F  // 'RX address pipe5' register address
+#define RG_TX_ADDR         0x10  // 'TX address' register address
+#define RG_RX_PW_P0        0x11  // 'RX payload width, pipe0' register address
+#define RG_RX_PW_P1        0x12  // 'RX payload width, pipe1' register address
+#define RG_RX_PW_P2        0x13  // 'RX payload width, pipe2' register address
+#define RG_RX_PW_P3        0x14  // 'RX payload width, pipe3' register address
+#define RG_RX_PW_P4        0x15  // 'RX payload width, pipe4' register address
+#define RG_RX_PW_P5        0x16  // 'RX payload width, pipe5' register address
+#define RG_FIFO_STATUS     0x17  // 'FIFO Status Register' register address
+#define RG_DYNPD           0x1C  // 'Enable dynamic payload length
+#define RG_FEATURE         0x1D  // 'Feature register
+
+#define RD_STATUS_TX_FULL 0x01 // tx queue full
+#define RD_STATUS_RX_PNO  0x0E // pipe number of the received payload
+#define RD_STATUS_MAX_RT  0x10 // max retransmissions
+#define RD_STATUS_TX_DS   0x20 // data sent
+#define RD_STATUS_RX_DR   0x40 // data ready
+
+#define RD_CONFIG_PRIM_RX 0x01 // is primary receiver
+#define RD_CONFIG_PWR_UP  0x02 // power up
+#define RD_CONFIG_CRCO    0x04 // 2-byte CRC
+#define RD_CONFIG_EN_CRC  0x08 // enable CRC
+#define RD_CONFIG_DISABLE_IRQ_MAX_RT 0x10
+#define RD_CONFIG_DISABLE_IRQ_TX_DS 0x20
+#define RD_CONFIG_DISABLE_IRQ_RX_DR 0x40
+
+#define RD_FIFO_STATUS_RX_EMPTY 0x01
+#define RD_FIFO_STATUS_RX_FULL 0x02
+#define RD_FIFO_STATUS_TX_EMPTY 0x10
+#define RD_FIFO_STATUS_TX_FULL 0x20
+#define RD_FIFO_STATUS_TX_REUSE 0x40
+
+// Config register bits (excluding the bottom two that are changed dynamically)
+// enable only Rx IRQ
+#define ModeBits (RD_CONFIG_DISABLE_IRQ_MAX_RT | \
+                  RD_CONFIG_DISABLE_IRQ_TX_DS | \
+                  RD_CONFIG_EN_CRC | \
+                  RD_CONFIG_CRCO)
+
+static inline uint8_t CS(uint8_t hl)
+{
+    if (hl == 1) {
+        NSS(0);
+    }
+    else {
+        NSS(1);
+    }
+    return hl;
+}
+
+#define CHIPSELECT for (uint8_t cs = CS(1); cs==1; cs = CS(0))
+
+// Base NRF address - byte 4 may be modified before writing to a pipe register,
+// the first 4 bytes are shared in the network. Master is always code 0.
+static uint8_t nrf_base_address[5];
+
+static uint8_t nrf_pipe_addr[6];
+static bool nrf_pipe_enabled[6];
+
+static uint8_t NRF_WriteRegister(uint8_t reg, uint8_t value)
+{
+    uint8_t status = 0;
+    CHIPSELECT {
+        status = spi(CMD_WRITE_REG | reg);
+        spi(value);
+    }
+    dbg_nrf("Wr[0x%02x] := 0x%02x", (int)reg, (int) value);
+
+
+    uint8_t reg_val = 0;
+    CHIPSELECT {
+        spi(CMD_READ_REG | reg);
+        reg_val = spi(0);
+    }
+    dbg_nrf("     verify 0x%02x", (int)reg_val);
+    if (reg_val != value)
+        dbg_nrf("                           !!!");
+    else
+        dbg_nrf("                           OK");
+
+
+    return status;
+}
+
+static uint8_t NRF_ReadRegister(uint8_t reg)
+{
+    uint8_t reg_val = 0;
+    CHIPSELECT {
+        spi(CMD_READ_REG | reg);
+        reg_val = spi(0);
+    }
+    dbg_nrf("Rd[0x%02x]  = 0x%02x", (int)reg, (int) reg_val);
+    return reg_val;
+}
+
+static uint8_t NRF_ReadStatus(void)
+{
+    uint8_t reg_val = 0;
+    CHIPSELECT {
+        reg_val = spi(CMD_NOP);
+    }
+    return reg_val;
+}
+
+static uint8_t NRF_WriteBuffer(uint8_t reg, const uint8_t *pBuf, uint8_t bytes)
+{
+    uint8_t status = 0, i = 0;
+    CHIPSELECT {
+        status = spi(CMD_WRITE_REG | reg);
+        for (i = 0; i < bytes; i++) {
+            spi(*pBuf++);
+        }
+    }
+    return status;
+}
+
+static uint8_t NRF_ReadBuffer(uint8_t reg, uint8_t *pBuf, uint8_t bytes)
+{
+    uint8_t status = 0, i;
+    CHIPSELECT {
+        status = spi(CMD_READ_REG | reg);
+        for (i = 0; i < bytes; i++) {
+            pBuf[i] = spi(0);
+        }
+    }
+    return status;
+}
+
+void NRF_SetBaseAddress(const uint8_t *Bytes4)
+{
+    memcpy(nrf_base_address, Bytes4, 4);
+    nrf_base_address[4] = 0;
+
+    // write it to the two full-width address registers
+    NRF_WriteBuffer(RG_RX_ADDR_P0, nrf_base_address, 5);
+    nrf_base_address[4] = 1;// to be different
+    NRF_WriteBuffer(RG_RX_ADDR_P1, nrf_base_address, 5);
+}
+
+void NRF_SetRxAddress(uint8_t pipenum, uint8_t AddrByte)
+{
+    if (pipenum > 5) {
+        dbg_nrf("!! bad pipe %d", pipenum);
+        return;
+    }
+
+    nrf_base_address[4] = AddrByte;
+
+    nrf_pipe_addr[pipenum] = AddrByte;
+
+    dbg_nrf("Set Rx addr (pipe %d) = 0x%02x", (int)pipenum, AddrByte);
+    if (pipenum == 0) {
+        dbg_nrf("W ADDR_PA0: %02X-%02X-%02X-%02X-%02X", nrf_base_address[0], nrf_base_address[1], nrf_base_address[2], nrf_base_address[3], nrf_base_address[4]);
+        NRF_WriteBuffer(RG_RX_ADDR_P0, nrf_base_address, 5);
+    }
+    else if (pipenum == 1) {
+        dbg_nrf("W ADDR_PA1: %02X-%02X-%02X-%02X-%02X", nrf_base_address[0], nrf_base_address[1], nrf_base_address[2], nrf_base_address[3], nrf_base_address[4]);
+        NRF_WriteBuffer(RG_RX_ADDR_P1, nrf_base_address, 5);
+    }
+    else {
+        NRF_WriteRegister(RG_RX_ADDR_P2 + (pipenum - 2), AddrByte);
+    }
+}
+
+bool NRF_AddPipe(uint8_t AddrByte, uint8_t *PipeNum)
+{
+    for (uint8_t i = 0; i < 6; i++) {
+        if(!nrf_pipe_enabled[i]) {
+            NRF_SetRxAddress(i, AddrByte);
+            *PipeNum = i;
+            NRF_EnablePipe(i);
+            return true;
+        }
+    }
+
+    return false;
+}
+
+uint8_t NRF_PipeNum2Addr(uint8_t pipe_num)
+{
+    if (pipe_num > 5) return 0; // fail
+    return nrf_pipe_addr[pipe_num];
+}
+
+uint8_t NRF_Addr2PipeNum(uint8_t addr)
+{
+    for (int i = 0; i < 6; i++) {
+        if (nrf_pipe_addr[i] == addr) return (uint8_t) i;
+    }
+    return 0xFF;
+}
+
+void NRF_EnablePipe(uint8_t pipenum)
+{
+    dbg_nrf("Enable pipe num %d", (int)pipenum);
+    uint8_t enabled = NRF_ReadRegister(RG_EN_RXADDR);
+    enabled |= 1 << pipenum;
+    NRF_WriteRegister(RG_EN_RXADDR, enabled);
+
+    nrf_pipe_enabled[pipenum] = 1;
+}
+
+void NRF_DisablePipe(uint8_t pipenum)
+{
+    uint8_t enabled = NRF_ReadRegister(RG_EN_RXADDR);
+    enabled &= ~(1 << pipenum);
+    NRF_WriteRegister(RG_EN_RXADDR, enabled);
+
+    nrf_pipe_enabled[pipenum] = 0;
+}
+
+static void NRF_SetTxAddress(uint8_t SendTo)
+{
+    nrf_base_address[4] = SendTo;
+
+    dbg_nrf("W Tx_ADDR + Rx0: %02X-%02X-%02X-%02X-%02X",
+        nrf_base_address[0], nrf_base_address[1], nrf_base_address[2], nrf_base_address[3], nrf_base_address[4]);
+
+    NRF_WriteBuffer(RG_TX_ADDR, nrf_base_address, 5);
+    NRF_WriteBuffer(RG_RX_ADDR_P0, nrf_base_address, 5); // the ACK will come to pipe 0
+}
+
+void NRF_PowerDown(void)
+{
+    dbg_nrf("PDn");
+    CE(0);
+    NRF_WriteRegister(RG_CONFIG, ModeBits);
+}
+
+void NRF_ModeTX(void)
+{
+    dbg_nrf("Tx Mode");
+
+    CE(0);
+    uint8_t m = NRF_ReadRegister(RG_CONFIG);
+    NRF_WriteRegister(RG_CONFIG, ModeBits | RD_CONFIG_PWR_UP);
+    if ((m & RD_CONFIG_PWR_UP) == 0) {
+        // switching on
+        LL_mDelay(5);
+    }
+}
+
+void NRF_ModeRX(void)
+{
+    dbg_nrf("Rx Mode");
+    NRF_WriteRegister(RG_CONFIG, ModeBits | RD_CONFIG_PWR_UP | RD_CONFIG_PRIM_RX);
+    NRF_SetRxAddress(0, nrf_pipe_addr[0]); // set the P0 address - it was changed during Rx for ACK reception
+    CE(1);
+
+    //if ((m&2)==0) LL_mDelay()(5); You don't need to wait. Just nothing will come for 5ms or more
+}
+
+uint8_t NRF_IsModePowerDown(void)
+{
+    uint8_t ret = 0;
+    if ((NRF_ReadRegister(RG_CONFIG) & RD_CONFIG_PWR_UP) == 0) ret = 1;
+    return ret;
+}
+
+uint8_t NRF_IsModeTX(void)
+{
+    uint8_t m = NRF_ReadRegister(RG_CONFIG);
+    if ((m & RD_CONFIG_PWR_UP) == 0) return 0; // OFF
+    if ((m & RD_CONFIG_PRIM_RX) == 0) return 1;
+    return 0;
+}
+
+uint8_t NRF_IsModeRx(void)
+{
+    uint8_t m = NRF_ReadRegister(RG_CONFIG);
+    if ((m & RD_CONFIG_PWR_UP) == 0) return 0; // OFF
+    if ((m & RD_CONFIG_PRIM_RX) == 0) return 0;
+    return 1;
+}
+
+void NRF_SetChannel(uint8_t Ch)
+{
+    NRF_WriteRegister(RG_RF_CH, Ch);
+}
+
+uint8_t NRF_ReceivePacket(uint8_t *Packet, uint8_t *PipeNum)
+{
+    uint8_t pw = 0, status;
+//    if (!NRF_IsRxPacket()) {
+//        dbg("rx queue empty");
+//        return 0;
+//    }
+
+//    const uint8_t orig_conf = NRF_ReadRegister(RG_CONFIG);
+//    CE(0); // quit Rx mode - go idle
+
+    CHIPSELECT {
+        status = spi(CMD_RD_RX_PL_WIDTH);
+        pw = spi(0);
+    }
+
+    if (pw == 0) {
+        dbg("empty pld");
+    }
+
+    if (pw > 32) {
+        CHIPSELECT {
+            spi(CMD_FLUSH_RX);
+        }
+        pw = 0;
+        dbg("over 32");
+    } else {
+        // Read the reception pipe number
+        *PipeNum = ((status & RD_STATUS_RX_PNO) >> 1);
+        CHIPSELECT {
+            spi(CMD_RD_RX_PLD);
+            for (uint8_t i = 0; i < pw; i++) Packet[i] = spi(0);
+        }
+    }
+    NRF_WriteRegister(RG_STATUS, RD_STATUS_RX_DR); // Clear the RX_DR interrupt
+
+//    if ((orig_conf & RD_CONFIG_PWR_UP) == 0) {
+//        dbg_nrf("going back PwrDn");
+//        NRF_PowerDown();
+//    }
+//    else if ((orig_conf & RD_CONFIG_PRIM_RX) == RD_CONFIG_PRIM_RX) {
+//        dbg_nrf("going back PwrUp+Rx");
+//        NRF_ModeRX();
+//    }
+//    CE(1); // back to rx
+    return pw;
+}
+
+bool NRF_IsRxPacket(void)
+{
+    return 0 == (NRF_ReadRegister(RG_FIFO_STATUS) & RD_FIFO_STATUS_RX_EMPTY);
+//    uint8_t ret = NRF_ReadRegister(RG_STATUS) & RD_STATUS_RX_DR;
+//    return 0 != ret;
+}
+
+bool NRF_SendPacket(uint8_t PipeNum, const uint8_t *Packet, uint8_t Length)
+{
+    if (!nrf_pipe_enabled[PipeNum]) {
+        dbg_nrf("!! Pipe %d not enabled", PipeNum);
+        return 0;
+    }
+
+    dbg_nrf("Will tx to addr %02x", nrf_pipe_addr[PipeNum]);
+
+    const uint8_t orig_conf = NRF_ReadRegister(RG_CONFIG);
+    CE(0);
+    NRF_ModeTX();        // Make sure in TX mode
+    NRF_SetTxAddress(nrf_pipe_addr[PipeNum]); // this sets the Tx addr and also pipe 0 addr for ACK
+
+    CHIPSELECT {
+        spi(CMD_FLUSH_TX);
+    };
+
+    CHIPSELECT {
+        spi(CMD_WR_TX_PLD);
+        for (uint8_t i = 0; i < Length; i++) spi(Packet[i]);
+    };
+
+    // CE pulse
+    CE(1);
+    _delay_us(20); // At least 10 us
+    CE(0);
+
+    uint8_t st = 0;
+    while ((st & (RD_STATUS_MAX_RT|RD_STATUS_TX_DS)) == 0) {
+        st = NRF_ReadStatus(); // Packet acked or timed out
+    }
+
+    dbg_nrf("Send status: 0x%02x - MAX_RT %d, SENT %d", (int)st,
+        (st&RD_STATUS_MAX_RT) != 0, (st&RD_STATUS_TX_DS) != 0);
+
+    NRF_WriteRegister(RG_STATUS, st & (RD_STATUS_MAX_RT|RD_STATUS_TX_DS)); // Clear the bit
+
+    if ((orig_conf & RD_CONFIG_PWR_UP) == 0) {
+        dbg_nrf("going back PwrDn");
+        NRF_PowerDown();
+    }
+    else if ((orig_conf & RD_CONFIG_PRIM_RX) == RD_CONFIG_PRIM_RX) {
+        dbg_nrf("going back PwrUp+Rx");
+        NRF_ModeRX();
+    }
+
+    return 0 != (st & RD_STATUS_TX_DS); // success
+}
+
+void NRF_Init(uint8_t pSpeed)
+{
+    // Set the required output pins
+    NSS(1);
+    CE(0);
+
+    LL_mDelay(200);
+
+    for (int i = 0; i < 6; i++) {
+        nrf_pipe_addr[i] = 0;
+        nrf_pipe_enabled[i] = 0;
+    }
+
+    // clear flags etc
+    NRF_PowerDown();
+    CHIPSELECT { spi(CMD_FLUSH_RX); }
+    CHIPSELECT { spi(CMD_FLUSH_TX); }
+    NRF_WriteRegister(RG_STATUS, 0x70);
+
+    NRF_WriteRegister(RG_CONFIG, ModeBits);
+    NRF_WriteRegister(RG_SETUP_AW, 0b11);             // 5 byte addresses
+
+    NRF_WriteRegister(RG_EN_RXADDR, 0x01); // disable all, enable pipe 0 - this is required for shockburst, despite not being specified in the DS
+
+    NRF_WriteRegister(RG_SETUP_RETR, 0x18);        // 8 retries
+    NRF_WriteRegister(RG_RF_CH, 2);                // channel 2 NO HIGHER THAN 83 in USA!
+
+    NRF_WriteRegister(RG_RF_SETUP, pSpeed);
+
+    NRF_WriteRegister(RG_DYNPD, 0b111111);         // Dynamic packet length
+    NRF_WriteRegister(RG_FEATURE, 0b100);          // Enable dynamic payload, and no payload in the ack.
+
+//    for (int i = 0; i < 6; i++) {
+//        NRF_WriteRegister(RG_RX_PW_P0+i, 32);      // Receive 32 byte packets - XXX this is probably not needed with dynamic length
+//    }
+}
diff --git a/comm/nrf.h b/comm/nrf.h
new file mode 100644
index 0000000..e671d71
--- /dev/null
+++ b/comm/nrf.h
@@ -0,0 +1,157 @@
+//
+// Created by MightyPork on 2018/04/02.
+//
+
+#ifndef GEX_NRF_NRF_H
+#define GEX_NRF_NRF_H
+
+/*
+ * nordic.h
+ *
+ * Created:12/16/2013 3:36:04 PM
+ *  Author: Tom
+ *
+ *    NRF24L01+ Library II
+ *
+ */
+
+
+#ifndef NORDIC_H_
+#define NORDIC_H_
+
+#include "platform.h"
+#include "resources.h"
+#include "nrf_pins.h"
+
+#define dbg_nrf(...) do{}while(0)
+//#define dbg_nrf(...) dbg(##__VA_ARGS__)
+
+// Initialize SPI and the Nordic
+
+/**
+ * Initialize the NRF module
+ *
+ * @param pSpeed
+ */
+void NRF_Init(uint8_t pSpeed);
+
+#define NRF_SPEED_500k 0b00100110
+#define NRF_SPEED_2M 0b00001110
+#define NRF_SPEED_1M 0b00000110
+
+/**
+ * Set reception address
+ * @param pipenum - pipe to set
+ * @param AddrByte - byte 0
+ */
+void NRF_SetRxAddress(uint8_t pipenum, uint8_t AddrByte);
+
+/**
+ * Set communication channel
+ */
+void NRF_SetChannel(uint8_t Ch) ; // 0 through 83 only!
+
+/**
+ * Power down the transceiver
+ */
+void NRF_PowerDown(void);
+
+/**
+ * Selecr RX mode
+ */
+void NRF_ModeRX(void);
+
+/**
+ * Select TX mode
+ */
+void NRF_ModeTX(void);
+
+/**
+ * @return NRF is power down
+ */
+uint8_t NRF_IsModePowerDown(void);
+
+/**
+ * @return NRF in TX mode
+ */
+uint8_t NRF_IsModeTX(void);
+
+/**
+ * @return NRF in RX mode
+ */
+uint8_t NRF_IsModeRx(void);
+
+/**
+ * Add a pipe to the next free slot
+ *
+ * @param AddrByte - address byte of the peer
+ * @param[out] PipeNum - pipe number is written here
+ * @return success
+ */
+bool NRF_AddPipe(uint8_t AddrByte, uint8_t *PipeNum);
+
+/**
+ * Convert pipe number to address byte
+ *
+ * @param pipe_num - pipe number
+ * @return address byte
+ */
+uint8_t NRF_PipeNum2Addr(uint8_t pipe_num);
+
+/**
+ * Convert address to a pipe number
+ *
+ * @param addr
+ * @return
+ */
+uint8_t NRF_Addr2PipeNum(uint8_t addr);
+
+/**
+ * Send a packet (takes care of mode switching etc)
+ *
+ * @param PipeNum - pipe number
+ * @param Packet - packet bytes
+ * @param Length - packet length
+ * @return success (ACK'd)
+ */
+bool NRF_SendPacket(uint8_t PipeNum, const uint8_t *Packet, uint8_t Length);
+
+/**
+ * Receive a packet
+ *
+ * @param[out] Packet - the receiuved packet - buffer that is written
+ * @param[out] PipeNum - pipe number that was received from
+ * @return packet size, 0 on failure
+ */
+uint8_t NRF_ReceivePacket(uint8_t *Packet, uint8_t *PipeNum);
+
+/**
+ * Set base address
+ * @param Bytes4
+ */
+void NRF_SetBaseAddress(const uint8_t *Bytes4);
+
+/**
+ * Check if there's a packet to be read
+ *
+ * @return 1 if any to read
+ */
+bool NRF_IsRxPacket(void);
+
+/**
+ * Enable a pipe
+ *
+ * @param pipenum - pipe number 0-5
+ */
+void NRF_EnablePipe(uint8_t pipenum);
+
+/**
+ * Disable a pipe
+ *
+ * @param pipenum - pipe number 0-5
+ */
+void NRF_DisablePipe(uint8_t pipenum);
+
+#endif /* NORDIC_H_ */
+
+#endif //GEX_NRF_NRF_H
diff --git a/comm/nrf_pins.h b/comm/nrf_pins.h
new file mode 100644
index 0000000..c30b4aa
--- /dev/null
+++ b/comm/nrf_pins.h
@@ -0,0 +1,33 @@
+//
+// Created by MightyPork on 2018/04/06.
+//
+
+#ifndef GEX_F072_NRF_PINS_H
+#define GEX_F072_NRF_PINS_H
+
+#include "platform.h"
+
+// TODO move those to plat_compat?
+#define NRF_SPI            SPI1
+#define NRF_R_SPI          R_SPI1
+
+#define NRF_IRQ_Pin        LL_GPIO_PIN_10
+#define NRF_IRQ_GPIO_Port  GPIOB
+#define NRF_R_IRQ          R_PB10
+#define NRF_EXTI_LINENUM   10
+#define NRF_SYSCFG_EXTI_PORT LL_SYSCFG_EXTI_PORTB
+
+#define NRF_NSS_Pin        LL_GPIO_PIN_11
+#define NRF_NSS_GPIO_Port  GPIOB
+#define NRF_R_NSS          R_PB11
+
+#define NRF_CE_Pin         LL_GPIO_PIN_12
+#define NRF_CE_GPIO_Port   GPIOB
+#define NRF_R_CE           R_PB12
+
+#define NRF_R_SCK          R_PA5
+#define NRF_R_MISO         R_PA6
+#define NRF_R_MOSI         R_PA7
+#define NRF_SPI_AF         LL_GPIO_AF_0
+
+#endif //GEX_F072_NRF_PINS_H
diff --git a/framework/system_settings.c b/framework/system_settings.c
index 8e49142..affead3 100644
--- a/framework/system_settings.c
+++ b/framework/system_settings.c
@@ -2,8 +2,6 @@
 // Created by MightyPork on 2017/12/02.
 //
 
-#include <platform/debug_uart.h>
-#include <comm/interfaces.h>
 #include "platform.h"
 #include "system_settings.h"
 #include "utils/str_utils.h"
@@ -11,6 +9,8 @@
 #include "cfg_utils.h"
 #include "resources.h"
 #include "unit_base.h"
+#include "platform/debug_uart.h"
+#include "comm/interfaces.h"
 
 static void systemsettings_mco_teardown(void);
 static void systemsettings_mco_init(void);
@@ -32,6 +32,15 @@ void systemsettings_loadDefaults(void)
     SystemSettings.use_comm_nordic = false;
     SystemSettings.comm_uart_baud = 115200; // TODO
 
+    // just a demo, user must change this
+    SystemSettings.nrf_network[0] = 0x12;
+    SystemSettings.nrf_network[2] = 0x09;
+    SystemSettings.nrf_network[3] = 0x4c;
+    SystemSettings.nrf_network[4] = 0x61;
+
+    SystemSettings.nrf_address = 1;
+    SystemSettings.nrf_channel = 76;
+
     SystemSettings.enable_debug_uart = true;
 }
 
@@ -49,7 +58,7 @@ void systemsettings_init(void)
 void systemsettings_save(PayloadBuilder *pb)
 {
     pb_char(pb, 'S');
-    pb_u8(pb, 2); // settings format version
+    pb_u8(pb, 3); // settings format version
 
     { // system settings
         pb_bool(pb, SystemSettings.visible_vcom);
@@ -63,9 +72,52 @@ void systemsettings_save(PayloadBuilder *pb)
         pb_bool(pb, SystemSettings.use_comm_lora);
         pb_u32(pb, SystemSettings.comm_uart_baud);
         pb_bool(pb, SystemSettings.enable_debug_uart);
+        // 3
+        pb_u8(pb, SystemSettings.nrf_channel);
+        pb_u8(pb, SystemSettings.nrf_address);
+        pb_buf(pb, SystemSettings.nrf_network, 4);
     } // end system settings
 }
 
+
+// from binary
+bool systemsettings_load(PayloadParser *pp)
+{
+    if (pp_char(pp) != 'S') return false;
+
+    systemsettings_begin_load();
+
+    uint8_t version = pp_u8(pp);
+
+    { // system settings
+        SystemSettings.visible_vcom = pp_bool(pp);
+        SystemSettings.ini_comments = pp_bool(pp);
+
+        // conditional fields based on version
+        if (version >= 1) {
+            SystemSettings.enable_mco = pp_bool(pp);
+            SystemSettings.mco_prediv = pp_u8(pp);
+        }
+        if (version >= 2) {
+            SystemSettings.use_comm_uart = pp_bool(pp);
+            SystemSettings.use_comm_nordic = pp_bool(pp);
+            SystemSettings.use_comm_lora = pp_bool(pp);
+            SystemSettings.comm_uart_baud = pp_u32(pp);
+            SystemSettings.enable_debug_uart = pp_bool(pp);
+        }
+        if (version >= 3) {
+            SystemSettings.nrf_channel = pp_u8(pp);
+            SystemSettings.nrf_address = pp_u8(pp);
+            pp_buf(pp, SystemSettings.nrf_network, 4);
+        }
+    } // end system settings
+
+    systemsettings_finalize_load();
+
+    return pp->ok;
+}
+
+
 void systemsettings_mco_teardown(void)
 {
     if (SystemSettings.enable_mco) {
@@ -80,8 +132,7 @@ void systemsettings_mco_init(void)
         assert_param(rsc_claim(&UNIT_SYSTEM, R_PA8) == E_SUCCESS);
 
         assert_param(E_SUCCESS == hw_configure_gpiorsc_af(R_PA8, LL_GPIO_AF_0));
-        LL_RCC_ConfigMCO(LL_RCC_MCO1SOURCE_SYSCLK,
-                         SystemSettings.mco_prediv << RCC_CFGR_MCOPRE_Pos);
+        LL_RCC_ConfigMCO(LL_RCC_MCO1SOURCE_SYSCLK, SystemSettings.mco_prediv << RCC_CFGR_MCOPRE_Pos);
     } else {
         LL_RCC_ConfigMCO(LL_RCC_MCO1SOURCE_NOCLOCK, 0);
     }
@@ -115,39 +166,6 @@ void systemsettings_finalize_load(void)
     com_claim_resources_for_alt_transfers();
 }
 
-// from binary
-bool systemsettings_load(PayloadParser *pp)
-{
-    if (pp_char(pp) != 'S') return false;
-
-    systemsettings_begin_load();
-
-    uint8_t version = pp_u8(pp);
-
-    { // system settings
-        SystemSettings.visible_vcom = pp_bool(pp);
-        SystemSettings.ini_comments = pp_bool(pp);
-
-        // conditional fields based on version
-        if (version >= 1) {
-            SystemSettings.enable_mco = pp_bool(pp);
-            SystemSettings.mco_prediv = pp_u8(pp);
-        }
-        if (version >= 2) {
-            SystemSettings.use_comm_uart = pp_bool(pp);
-            SystemSettings.use_comm_nordic = pp_bool(pp);
-            SystemSettings.use_comm_lora = pp_bool(pp);
-            SystemSettings.comm_uart_baud = pp_u32(pp);
-            SystemSettings.enable_debug_uart = pp_bool(pp);
-        }
-    } // end system settings
-
-    systemsettings_finalize_load();
-
-    return pp->ok;
-}
-
-
 /**
  * Write system settings to INI (without section)
  */
@@ -171,18 +189,33 @@ void systemsettings_build_ini(IniWriter *iw)
     iw_entry_d(iw, "mco-prediv", (1<<SystemSettings.mco_prediv));
 
     iw_cmt_newline(iw);
-    iw_comment(iw, "Allowed fallback communication ports");
+    iw_comment(iw, "--- Allowed fallback communication ports ---");
 
-    iw_comment(iw, "UART Tx:PA2, Rx:PA2");
+    iw_cmt_newline(iw);
+    iw_comment(iw, "UART Tx:PA2, Rx:PA3");
     iw_entry_s(iw, "com-uart", str_yn(SystemSettings.use_comm_uart));
     iw_entry_d(iw, "com-uart-baud", SystemSettings.comm_uart_baud);
 
+    iw_cmt_newline(iw);
+    iw_comment(iw, "nRF24L01+ radio");
+    iw_entry_s(iw, "com-nrf", str_yn(SystemSettings.use_comm_nordic));
+
+    iw_comment(iw, "Radio channel (0-125)");
+    iw_entry_d(iw, "nrf-channel", SystemSettings.nrf_channel);
+
+    iw_comment(iw, "Network prefix (hex, 4 bytes)");
+    iw_entry(iw, "nrf-network", "%02X:%02X:%02X:%02X",
+             SystemSettings.nrf_network[0],
+             SystemSettings.nrf_network[1],
+             SystemSettings.nrf_network[2],
+             SystemSettings.nrf_network[3]);
+
+    iw_comment(iw, "Node address (1-255)");
+    iw_entry(iw, "nrf-address", "%d", (int)SystemSettings.nrf_address);
+
     // those aren't implement yet, don't tease the user
     // TODO show pin-out, extra settings if applicable
 #if 0
-    iw_comment(iw, "nRF24L01+");
-    iw_entry_s(iw, "com-nordic", str_yn(SystemSettings.use_comm_nrf24l01p));
-
     iw_comment(iw, "LoRa/GFSK sx127x");
     iw_entry_s(iw, "com-lora", str_yn(SystemSettings.use_comm_sx127x));
 #endif
@@ -241,12 +274,24 @@ bool systemsettings_load_ini(const char *restrict key, const char *restrict valu
         if (suc) SystemSettings.comm_uart_baud = baud;
     }
 
-#if 0
-    if (streq(key, "com-nordic")) {
+    if (streq(key, "com-nrf")) {
         bool yn = cfg_bool_parse(value, &suc);
         if (suc) SystemSettings.use_comm_nordic = yn;
     }
 
+    if (streq(key, "nrf-channel")) {
+        SystemSettings.nrf_channel = cfg_u8_parse(value, &suc);
+    }
+
+    if (streq(key, "nrf-address")) {
+        SystemSettings.nrf_address = cfg_u8_parse(value, &suc);
+    }
+
+    if (streq(key, "nrf-network")) {
+        cfg_hex_parse(&SystemSettings.nrf_network[0], 4, value, &suc);
+    }
+
+#if 0
     if (streq(key, "com-lora")) {
         bool yn = cfg_bool_parse(value, &suc);
         if (suc) SystemSettings.use_comm_lora = yn;
diff --git a/framework/system_settings.h b/framework/system_settings.h
index 94cf4da..1f866e9 100644
--- a/framework/system_settings.h
+++ b/framework/system_settings.h
@@ -27,6 +27,9 @@ struct system_settings {
     uint32_t comm_uart_baud; // baud rate for the uart transport
     bool use_comm_lora;   // SX1276/8
     bool use_comm_nordic; // nRF24L01+
+    uint8_t nrf_channel;
+    uint8_t nrf_network[4];
+    uint8_t nrf_address;
 
     // Support flags put here for scoping, but not atcually part of the persistent settings
     volatile bool editable; //!< True if we booted with the LOCK jumper removed
diff --git a/gex.mk b/gex.mk
index 5921c08..8fbd5e4 100644
--- a/gex.mk
+++ b/gex.mk
@@ -95,7 +95,7 @@ GEX_CDEFS = $(GEX_CDEFS_BASE) \
     -DDEBUG_VFS=0 \
     -DDEBUG_FLASH_WRITE=0 \
     -DVERBOSE_HARDFAULT=1 \
-    -DUSE_STACK_MONITOR=1 \
+    -DUSE_STACK_MONITOR=0 \
     -DUSE_DEBUG_UART=1 \
     -DDEBUG_MALLOC=0 \
     -DDEBUG_RSC=0
diff --git a/gex_hooks.c b/gex_hooks.c
index c0a920a..9da2fb5 100644
--- a/gex_hooks.c
+++ b/gex_hooks.c
@@ -11,13 +11,17 @@
 #include "gex_hooks.h"
 #include "unit_registry.h"
 #include "comm/interfaces.h"
+#include "system_settings.h"
 
 /**
  * This is a systick callback for GEX application logic
  */
 void GEX_MsTick(void)
 {
-    com_iface_flush_buffer();
+    if (gActiveComport == COMPORT_USART) {
+        com_iface_flush_buffer();
+    }
+
     TF_Tick(comm);
     Indicator_Tick();
     ureg_tick_units();
@@ -28,6 +32,11 @@ void GEX_MsTick(void)
  */
 void GEX_PreInit(void)
 {
+    // this is a hack to make logging of the initial messages work
+    // it's problematic because we shouldn't even enable the debug uart if it's disabled in the system settings
+    // TODO move system settings load earlier and check the uart flag in advance
+    SystemSettings.enable_debug_uart = true;
+
     __HAL_RCC_GPIOA_CLK_ENABLE();
     __HAL_RCC_GPIOB_CLK_ENABLE();
     __HAL_RCC_GPIOC_CLK_ENABLE();
diff --git a/platform/cfg_utils.c b/platform/cfg_utils.c
index b8bef60..83dce48 100644
--- a/platform/cfg_utils.c
+++ b/platform/cfg_utils.c
@@ -297,3 +297,46 @@ uint32_t cfg_enum4_parse(const char *value,
     *suc = false;
     return na;
 }
+
+void cfg_hex_parse(uint8_t *dest, uint32_t count, const char *value, bool *suc)
+{
+    // discard possible leading 0x
+    if (value[0] == '0' && value[1] == 'x') {
+        value += 2;
+    }
+
+    uint8_t bytebuf = 0;
+    for (uint32_t digit = 0; digit < count * 2;) {
+        char v = *value;
+        if (v != 0) value++;
+
+        uint8_t nibble = 0;
+        if (v == ' ' || v == '.' || v == ',' || v == '-' || v == ':') {
+            continue; // junk
+        }
+        else if (v >= '0' && v <= '9') {
+            nibble = (uint8_t) (v - '0');
+        }
+        else if (v >= 'a' && v <= 'f') {
+            nibble = (uint8_t) (10 + (v - 'a'));
+        }
+        else if (v >= 'A' && v <= 'F') {
+            nibble = (uint8_t) (10 + (v - 'A'));
+        }
+        else if (v == 0) {
+            nibble = 0; // pad with zeros
+        }
+        else {
+            *suc = false;
+            return;
+        }
+
+        digit++;
+        bytebuf <<= 4;
+        bytebuf |= nibble;
+        if ((digit % 2 == 0) && digit > 0) { // whole byte
+            *dest++ = bytebuf;
+            bytebuf = 0;
+        }
+    }
+}
diff --git a/platform/cfg_utils.h b/platform/cfg_utils.h
index 05f8ebe..de34c19 100644
--- a/platform/cfg_utils.h
+++ b/platform/cfg_utils.h
@@ -116,6 +116,18 @@ uint32_t cfg_enum4_parse(const char *tpl,
                          const char *d, uint32_t nd,
                          bool *suc);
 
+/**
+ * Parse a hexa string to a byte array.
+ * Skips 0x prefix, '.', '-', ':', ' '.
+ *
+ * @param[out] dest - storage array
+ * @param[in] count - expected number of bytes
+ * @param[in] value - parsed string
+ * @param[out] suc - success flag
+ */
+void cfg_hex_parse(uint8_t *dest, uint32_t count,
+                   const char *value, bool *suc);
+
 /** Convert bool to a Y or N constant string */
 #define str_yn(cond) ((cond) ? ("Y") : ("N"))
 
diff --git a/platform/platform.c b/platform/platform.c
index 4e1ebf3..b4dda15 100644
--- a/platform/platform.c
+++ b/platform/platform.c
@@ -41,6 +41,9 @@ void plat_init_resources(void)
         ureg_add_type(&UNIT_TEST);
     #endif
 
+    // EXTI are always available
+    rsc_free_range(NULL, R_EXTI0, R_EXTI15);
+
     // --- platform specific resource releases and claims ---
 
 #if defined(GEX_PLAT_F103_BLUEPILL)
diff --git a/units/digital_in/_din_init.c b/units/digital_in/_din_init.c
index 7d501ce..ff3edff 100644
--- a/units/digital_in/_din_init.c
+++ b/units/digital_in/_din_init.c
@@ -54,7 +54,19 @@ error_t DIn_init(Unit *unit)
     // Claim all needed pins
     TRY(rsc_claim_gpios(unit, priv->port_name, priv->pins));
 
-    uint16_t mask = 1;
+    uint16_t mask;
+
+    // claim the needed EXTIs
+    mask = 1;
+    for (int i = 0; i < 16; i++, mask <<= 1) {
+        if (priv->pins & mask) {
+            if ((priv->trig_rise|priv->trig_fall) & mask) {
+                TRY(rsc_claim(unit, R_EXTI0+i));
+            }
+        }
+    }
+
+    mask = 1;
     for (int i = 0; i < 16; i++, mask <<= 1) {
         if (priv->pins & mask) {
             uint32_t ll_pin = hw_pin2ll((uint8_t) i, &suc);