diff --git a/TinyFrame/TF_Integration.c b/TinyFrame/TF_Integration.c
index 6aa1b18..fb911df 100644
--- a/TinyFrame/TF_Integration.c
+++ b/TinyFrame/TF_Integration.c
@@ -4,11 +4,11 @@
 // TinyFrame integration
 //
 
-#include <USB/usb_device.h>
 #include "platform.h"
 #include "task_main.h"
 
 #include "USB/usbd_cdc_if.h"
+#include "USB/usb_device.h"
 #include "TinyFrame.h"
 
 extern osSemaphoreId semVcomTxReadyHandle;
@@ -16,6 +16,30 @@ extern osMutexId mutTinyFrameTxHandle;
 
 void TF_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) {
+        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)
+
+    // the assumption here is that all until the last chunk use the full buffer capacity
+    if (real_size == TF_SENDBUF_LEN) {
+        if (pdTRUE != xSemaphoreTake(semVcomTxReadyHandle, 100)) {
+            TF_Error("Tx stalled in WriteImpl");
+            return;
+        }
+    }
+#else
     (void) tf;
 #define CHUNK 64 // same as TF_SENDBUF_LEN, so we should always have only one run of the loop
     int32_t total = (int32_t) len;
@@ -37,16 +61,26 @@ void TF_WriteImpl(TinyFrame *tf, const uint8_t *buff, uint32_t len)
         buff += chunksize;
         total -= chunksize;
     }
+#endif
 }
 
 /** Claim the TX interface before composing and sending a frame */
 bool TF_ClaimTx(TinyFrame *tf)
 {
     (void) tf;
-//    assert_param(osThreadGetId() != tskMainHandle);
-    assert_param(!inIRQ());
+//    assert_param(!inIRQ()); // useless delay
+    assert_param(pdTRUE == xSemaphoreTake(mutTinyFrameTxHandle, 5000)); // trips the wd
+
+    // 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)) {
+        TF_Error("Tx stalled in Claim");
+
+        // release the guarding mutex again
+        assert_param(pdTRUE == xSemaphoreGive(mutTinyFrameTxHandle));
+        return false;
+    }
 
-    assert_param(osOK == osMutexWait(mutTinyFrameTxHandle, 5000));
     return true;
 }
 
@@ -54,5 +88,7 @@ bool TF_ClaimTx(TinyFrame *tf)
 void TF_ReleaseTx(TinyFrame *tf)
 {
     (void) tf;
-    assert_param(osOK == osMutexRelease(mutTinyFrameTxHandle));
+    assert_param(pdTRUE == xSemaphoreGive(mutTinyFrameTxHandle));
+
+    // the last payload is sent asynchronously
 }
diff --git a/TinyFrame/TinyFrame.c b/TinyFrame/TinyFrame.c
index 3489942..11f14b0 100644
--- a/TinyFrame/TinyFrame.c
+++ b/TinyFrame/TinyFrame.c
@@ -870,7 +870,11 @@ static inline uint32_t _TF_FN TF_ComposeTail(uint8_t *outbuff, TF_CKSUM *cksum)
  */
 static bool _TF_FN TF_SendFrame_Begin(TinyFrame *tf, TF_Msg *msg, TF_Listener listener, TF_TICKS timeout)
 {
-    TF_TRY(TF_ClaimTx(tf));
+    bool suc = TF_ClaimTx(tf);
+    if (!suc) {
+        TF_Error("TF lock not free");
+        return false;
+    }
 
     tf->tx_pos = (uint32_t) TF_ComposeHead(tf, tf->sendbuf, msg); // frame ID is incremented here if it's not a response
     tf->tx_len = msg->len;
@@ -1031,10 +1035,10 @@ bool _TF_FN TF_Query_Multipart(TinyFrame *tf, TF_Msg *msg, TF_Listener listener,
     return TF_Query(tf, msg, listener, timeout);
 }
 
-void _TF_FN TF_Respond_Multipart(TinyFrame *tf, TF_Msg *msg)
+bool _TF_FN TF_Respond_Multipart(TinyFrame *tf, TF_Msg *msg)
 {
     msg->data = NULL;
-    TF_Respond(tf, msg);
+    return TF_Respond(tf, msg);
 }
 
 void _TF_FN TF_Multipart_Payload(TinyFrame *tf, const uint8_t *buff, uint32_t length)
diff --git a/TinyFrame/TinyFrame.h b/TinyFrame/TinyFrame.h
index 5f6943c..7766aa1 100644
--- a/TinyFrame/TinyFrame.h
+++ b/TinyFrame/TinyFrame.h
@@ -369,7 +369,7 @@ bool TF_Query_Multipart(TinyFrame *tf, TF_Msg *msg, TF_Listener listener, TF_TIC
  * TF_Respond() with multipart payload.
  * msg.data is ignored and set to NULL
  */
-void TF_Respond_Multipart(TinyFrame *tf, TF_Msg *msg);
+bool TF_Respond_Multipart(TinyFrame *tf, TF_Msg *msg);
 
 /**
  * Send the payload for a started multipart frame. This can be called multiple times
diff --git a/USB/usbd_cdc_if.c b/USB/usbd_cdc_if.c
index b6ee7eb..b636985 100644
--- a/USB/usbd_cdc_if.c
+++ b/USB/usbd_cdc_if.c
@@ -314,7 +314,7 @@ void USBD_CDC_TransmitDone(USBD_HandleTypeDef *pdev)
   assert_param(inIRQ());
 
   portBASE_TYPE taskWoken = pdFALSE;
-  assert_param(xSemaphoreGiveFromISR(semVcomTxReadyHandle, &taskWoken) == pdTRUE);
+  assert_param(pdTRUE == xSemaphoreGiveFromISR(semVcomTxReadyHandle, &taskWoken));
   portYIELD_FROM_ISR(taskWoken);
 }
 /* USER CODE END PRIVATE_FUNCTIONS_IMPLEMENTATION */
diff --git a/comm/messages.c b/comm/messages.c
index 620a17e..7675504 100644
--- a/comm/messages.c
+++ b/comm/messages.c
@@ -65,7 +65,7 @@ static void settings_bulkread_cb(BulkRead *bulk, uint32_t chunk, uint8_t *buffer
     if (buffer == NULL) {
         free_ck(bulk);
         iw_end();
-        dbg("INI read complete.");
+//        dbg("INI read complete.");
         return;
     }
 
@@ -81,7 +81,7 @@ static void settings_bulkread_cb(BulkRead *bulk, uint32_t chunk, uint8_t *buffer
  */
 static TF_Result lst_ini_export(TinyFrame *tf, TF_Msg *msg)
 {
-    dbg("Bulk read INI file");
+//    dbg("Bulk read INI file");
 
     BulkRead *bulk = malloc_ck(sizeof(BulkRead));
     assert_param(bulk != NULL);
@@ -114,7 +114,7 @@ static void settings_bulkwrite_cb(BulkWrite *bulk, const uint8_t *chunk, uint32_
 
         if (bulk->offset > 0) {
             settings_load_ini_end();
-            dbg("INI write complete");
+//            dbg("INI write complete");
         } else {
             dbg("INI write failed");
         }
@@ -131,7 +131,7 @@ static void settings_bulkwrite_cb(BulkWrite *bulk, const uint8_t *chunk, uint32_
  */
 static TF_Result lst_ini_import(TinyFrame *tf, TF_Msg *msg)
 {
-    dbg("Bulk write INI file");
+//    dbg("Bulk write INI file");
 
     BulkWrite *bulk = malloc_ck(sizeof(BulkWrite));
     assert_param(bulk);
diff --git a/platform/plat_compat.h b/platform/plat_compat.h
index 74f1025..585aeb3 100644
--- a/platform/plat_compat.h
+++ b/platform/plat_compat.h
@@ -30,7 +30,7 @@
 
 
 #define BULK_READ_BUF_LEN 256   // Buffer for TF bulk reads
-#define UNIT_TMP_LEN      512   // Buffer for internal unit operations
+#define UNIT_TMP_LEN      256   // Buffer for internal unit operations
 
 #define FLASH_SAVE_BUF_LEN  128 // Malloc'd buffer for saving to flash
 
@@ -38,7 +38,7 @@
 #define RX_QUE_CAPACITY    16 // TinyFrame rx queue size (64 bytes each)
 
 #define TF_MAX_PAYLOAD_RX 512 // TF max Rx payload
-#define TF_SENDBUF_LEN     64 // TF transmit buffer (can be less than a full frame)
+#define TF_SENDBUF_LEN    512 // TF transmit buffer (can be less than a full frame)
 
 #define TF_MAX_ID_LST   4 // Frame ID listener count
 #define TF_MAX_TYPE_LST 6 // Frame Type listener count
diff --git a/units/adc/_adc_core.c b/units/adc/_adc_core.c
index 8a59d8e..c5e7a94 100644
--- a/units/adc/_adc_core.c
+++ b/units/adc/_adc_core.c
@@ -40,7 +40,8 @@ static void UADC_JobSendBlockChunk(Job *job)
         .len = (TF_LEN) (1 /*seq*/ + count * sizeof(uint16_t)),
         .type = type,
     };
-    TF_Respond_Multipart(comm, &msg);
+
+    assert_param(true == TF_Respond_Multipart(comm, &msg));
     TF_Multipart_Payload(comm, &priv->stream_serial, 1);
     TF_Multipart_Payload(comm, (uint8_t *) (priv->dma_buffer + start), count * sizeof(uint16_t));
     TF_Multipart_Close(comm);
@@ -171,7 +172,7 @@ static void handle_httc(Unit *unit, bool tc)
     const bool m_fixcpt = priv->opmode == ADC_OPMODE_BLCAP;
 
     if (ht) {
-        end = (priv->buf_itemcount / 2);
+        end = (priv->buf_itemcount >> 1); // div2
     }
     else {
         end = priv->buf_itemcount;
@@ -234,7 +235,7 @@ static void handle_httc(Unit *unit, bool tc)
         priv->stream_startpos = 0;
     }
     else {
-        priv->stream_startpos = priv->buf_itemcount / 2;
+        priv->stream_startpos = priv->buf_itemcount >> 1; // div2
     }
 }
 
@@ -289,7 +290,7 @@ void UADC_DMA_Handler(void *arg)
         const bool m_stream = priv->opmode == ADC_OPMODE_STREAM;
         const bool m_fixcpt = priv->opmode == ADC_OPMODE_BLCAP;
         if (m_trigd || m_stream || m_fixcpt) {
-            const uint32_t half = (uint32_t) (priv->buf_itemcount / 2);
+            const uint32_t half = (uint32_t) (priv->buf_itemcount >> 1); // div2
             if (ht && tc) {
                 // dual event interrupt - may happen if we missed both and they were pending after
                 // interrupts became enabled again (this can happen due to the EOS or other higher prio irq's)
@@ -336,8 +337,10 @@ void UADC_ADC_EOS_Handler(void *arg)
     if (priv->opmode == ADC_OPMODE_UNINIT) return;
 
     // Wait for the DMA to complete copying the last sample
-    uint32_t dmapos;
-    hw_wait_while((dmapos = DMA_POS(priv)) % priv->nb_channels != 0, 100); // XXX this could be changed to reading it from the DR instead
+    uint32_t dmapos = DMA_POS(priv);
+    if ((DMA_POS(priv) % priv->nb_channels) != 0) {
+        hw_wait_while((dmapos = DMA_POS(priv)) % priv->nb_channels != 0, 100); // XXX this could be changed to reading it from the DR instead
+    }
 
     uint32_t sample_pos;
     if (dmapos == 0) {