diff --git a/.gitignore b/.gitignore
index c6127b3..ffe84c0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -50,3 +50,6 @@ modules.order
 Module.symvers
 Mkfile.old
 dkms.conf
+
+.idea/
+cmake-build-debug/
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..e0ca3c5
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,31 @@
+cmake_minimum_required(VERSION 3.10)
+project(gex_client)
+
+set(CMAKE_C_STANDARD 99)
+
+set(SOURCE_FILES
+        main.c
+        gex/serial/serial.c
+        gex/serial/serial.h
+        gex/gex_client.c
+        gex/gex_client.h
+        gex/hexdump.c
+        gex/hexdump.h
+        gex/TF_Integration.c
+        gex/protocol/payload_builder.c
+        gex/protocol/payload_builder.h
+        gex/protocol/payload_parser.c
+        gex/protocol/payload_parser.h
+        gex/protocol/TF_Config.h
+        gex/protocol/TinyFrame.c
+        gex/protocol/TinyFrame.h
+        gex/protocol/type_coerce.h
+)
+
+include_directories(
+        gex
+        gex/protocol
+        gex/serial
+)
+
+add_executable(gex_client ${SOURCE_FILES})
diff --git a/gex/TF_Integration.c b/gex/TF_Integration.c
new file mode 100644
index 0000000..244f578
--- /dev/null
+++ b/gex/TF_Integration.c
@@ -0,0 +1,29 @@
+#include "TinyFrame.h"
+#include "gex_client.h"
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+#include <errno.h>
+
+void TF_WriteImpl(const uint8_t *buff, size_t len)
+{
+	assert(gex_serial_fd != 0);
+
+    ssize_t rv = write(gex_serial_fd, buff, len);
+	if (rv != len) {
+		fprintf(stderr, "ERROR %d in TF write: %s\n", errno, strerror(errno));
+	}
+}
+
+/** Claim the TX interface before composing and sending a frame */
+void TF_ClaimTx(void)
+{
+    //
+}
+
+/** Free the TX interface after composing and sending a frame */
+void TF_ReleaseTx(void)
+{
+    //
+}
diff --git a/gex/gex_client.c b/gex/gex_client.c
new file mode 100644
index 0000000..15a3059
--- /dev/null
+++ b/gex/gex_client.c
@@ -0,0 +1,102 @@
+//
+// Created by MightyPork on 2017/12/12.
+//
+
+#include <malloc.h>
+#include <assert.h>
+#include <unistd.h>
+#include <signal.h>
+#include  <stdlib.h>
+#include <protocol/TinyFrame.h>
+#include <string.h>
+#include <errno.h>
+
+#include "gex_client.h"
+#include "serial.h"
+#include "hexdump.h"
+
+int gex_serial_fd = -1;
+
+
+static void sigintHandler(int sig)
+{
+	if (gex_serial_fd != -1) {
+		close(gex_serial_fd);
+	}
+	exit(0);
+}
+
+TF_Result connectivityCheckCb(TF_Msg *msg)
+{
+	GexClient *gc = msg->userdata;
+	gc->connected = true;
+	fprintf(stderr, "GEX connected! Version string: %.*s\n", msg->len, msg->data);
+
+	msg->userdata = NULL;
+	return TF_CLOSE;
+}
+
+GexClient *GEX_Init(const char *device, int timeout_ms)
+{
+	assert(device != NULL);
+
+	GexClient *gc = calloc(1, sizeof(GexClient));
+	assert(gc != NULL);
+
+	// Bind ^C handler for safe shutdown
+	signal(SIGINT, sigintHandler);
+
+	// Open the device
+	gc->acm_device = device;
+	gc->acm_fd = serial_open(device, false, (timeout_ms+50)/100);
+	if (gc->acm_fd == -1) {
+		free(gc);
+		return NULL;
+	}
+
+	gex_serial_fd = gc->acm_fd;
+
+	// Test connectivity
+	TF_Msg msg;
+	TF_ClearMsg(&msg);
+	msg.type = 0x01; // TODO use constant
+	msg.userdata = gc;
+	TF_Query(&msg, connectivityCheckCb, 0);
+	GEX_Poll(gc);
+
+	if (!gc->connected) {
+		fprintf(stderr, "GEX doesn't respond to ping!\n");
+		GEX_DeInit(gc);
+		return NULL;
+	}
+
+	// TODO load and store unit callsigns + names
+
+	return gc;
+}
+
+
+void GEX_Poll(GexClient *gc)
+{
+	static uint8_t pollbuffer[4096];
+
+	assert(gc != NULL);
+
+	ssize_t len = read(gc->acm_fd, pollbuffer, 4096);
+	if (len < 0) {
+		fprintf(stderr, "ERROR %d in GEX Poll: %s\n", errno, strerror(errno));
+	} else {
+//		hexDump("Received", pollbuffer, (uint32_t) len);
+		TF_Accept(pollbuffer, (size_t) len);
+	}
+}
+
+
+void GEX_DeInit(GexClient *gc)
+{
+	if (gc == NULL) return;
+
+	close(gc->acm_fd);
+	gex_serial_fd = -1;
+	free(gc);
+}
diff --git a/gex/gex_client.h b/gex/gex_client.h
new file mode 100644
index 0000000..057b057
--- /dev/null
+++ b/gex/gex_client.h
@@ -0,0 +1,49 @@
+//
+// Created by MightyPork on 2017/12/12.
+//
+
+#ifndef GEX_CLIENT_GEX_CLIENT_H
+#define GEX_CLIENT_GEX_CLIENT_H
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+struct gex_client_ {
+	const char *acm_device;
+	int acm_fd;
+	bool connected;
+};
+
+typedef struct gex_client_ GexClient;
+
+/**
+ * Initialize the GEX client
+ *
+ * @param device - device, e.g. /dev/ttyACM0
+ * @param timeout_ms - read timeout in ms (allowed only multiples of 100 ms, others are rounded)
+ * @return an allocated client instance
+ */
+GexClient *GEX_Init(const char *device, int timeout_ms);
+
+/**
+ * Poll for new messages
+ * @param gc - client
+ */
+void GEX_Poll(GexClient *gc);
+
+/**
+ * Safely release all resources used up by GEX_Init()
+ *
+ * @param gc - the allocated client structure
+ */
+void GEX_DeInit(GexClient *gc);
+
+// --- Internal ---
+/**
+ * This is accessed by TF_WriteImpl().
+ * To be removed once TF supports multiple instances, i.e. without globals
+ */
+extern int gex_serial_fd;
+
+#endif //GEX_CLIENT_GEX_CLIENT_H
diff --git a/gex/hexdump.c b/gex/hexdump.c
new file mode 100644
index 0000000..6c51edc
--- /dev/null
+++ b/gex/hexdump.c
@@ -0,0 +1,61 @@
+//
+// Created by MightyPork on 2017/12/04.
+//
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include "hexdump.h"
+
+void hexDump(const char *restrict desc, const void *restrict addr, uint32_t len)
+{
+    uint32_t i;
+    uint8_t buff[17];
+    uint8_t *pc = (unsigned char*)addr;
+
+    // Output description if given.
+    if (desc != NULL)
+        fprintf(stderr, "%s:\r\n", desc);
+
+    if (len == 0) {
+        fprintf(stderr, "  ZERO LENGTH\r\n");
+        return;
+    }
+
+    // Process every byte in the data.
+    for (i = 0; i < len; i++) {
+        // Multiple of 16 means new line (with line offset).
+
+        if ((i % 16) == 0) {
+            // Just don't print ASCII for the zeroth line.
+            if (i != 0)
+                fprintf(stderr, "  %s\r\n", buff);
+
+            // Output the offset.
+            fprintf(stderr, "  %04"PRIx32" ", i);
+        }
+
+        // Now the hex code for the specific character.
+        fprintf(stderr, " %02x", pc[i]);
+
+        // And store a printable ASCII character for later.
+        if ((pc[i] < 0x20) || (pc[i] > 0x7e))
+            buff[i % 16] = '.';
+        else
+            buff[i % 16] = pc[i];
+        buff[(i % 16) + 1] = '\0';
+    }
+
+    // Pad out last line if not exactly 16 characters.
+    while ((i % 16) != 0) {
+        fprintf(stderr, "   ");
+        i++;
+    }
+
+    // And print the final ASCII bit.
+    fprintf(stderr, "  %s\r\n", buff);
+
+    (void)buff;
+}
diff --git a/gex/hexdump.h b/gex/hexdump.h
new file mode 100644
index 0000000..c1de480
--- /dev/null
+++ b/gex/hexdump.h
@@ -0,0 +1,19 @@
+//
+// Created by MightyPork on 2017/12/04.
+//
+
+#ifndef GEX_HEXDUMP_H
+#define GEX_HEXDUMP_H
+
+#include <stdint.h>
+
+/**
+ * HEXDUMP https://stackoverflow.com/a/7776146/2180189
+ *
+ * @param desc - description printed above the dump
+ * @param addr - address to dump
+ * @param len - number of bytes
+ */
+void hexDump(const char *restrict desc, const void *restrict addr, uint32_t len);
+
+#endif //GEX_HEXDUMP_H
diff --git a/gex/protocol/TF_Config.h b/gex/protocol/TF_Config.h
new file mode 100644
index 0000000..4dc088d
--- /dev/null
+++ b/gex/protocol/TF_Config.h
@@ -0,0 +1,72 @@
+//
+// Rename to TF_Config.h
+//
+
+#ifndef TF_CONFIG_H
+#define TF_CONFIG_H
+
+#include <stdint.h>
+//#include <esp8266.h> // when using with esphttpd
+
+//----------------------------- FRAME FORMAT ---------------------------------
+// The format can be adjusted to fit your particular application needs
+
+// If the connection is reliable, you can disable the SOF byte and checksums.
+// That can save up to 9 bytes of overhead.
+
+// ,-----+----+-----+------+------------+- - - -+------------,
+// | SOF | ID | LEN | TYPE | HEAD_CKSUM | DATA  | PLD_CKSUM  |
+// | 1   | ?  | ?   | ?    | ?          | ...   | ?          | <- size (bytes)
+// '-----+----+-----+------+------------+- - - -+------------'
+
+// !!! BOTH SIDES MUST USE THE SAME SETTINGS !!!
+
+// Adjust sizes as desired (1,2,4)
+#define TF_ID_BYTES     2
+#define TF_LEN_BYTES    2
+#define TF_TYPE_BYTES   1
+
+// Checksum type
+//#define TF_CKSUM_TYPE TF_CKSUM_NONE
+#define TF_CKSUM_TYPE TF_CKSUM_XOR
+//#define TF_CKSUM_TYPE TF_CKSUM_CRC16
+//#define TF_CKSUM_TYPE TF_CKSUM_CRC32
+
+// Use a SOF byte to mark the start of a frame
+#define TF_USE_SOF_BYTE 1
+// Value of the SOF byte (if TF_USE_SOF_BYTE == 1)
+#define TF_SOF_BYTE     0x01
+
+//----------------------- PLATFORM COMPATIBILITY ----------------------------
+
+// used for timeout tick counters - should be large enough for all used timeouts
+typedef uint16_t TF_TICKS;
+
+// used in loops iterating over listeners
+typedef uint8_t TF_COUNT;
+
+//----------------------------- PARAMETERS ----------------------------------
+
+// Maximum received payload size (static buffer)
+// Larger payloads will be rejected.
+#define TF_MAX_PAYLOAD_RX 4096
+// Size of the sending buffer. Larger payloads will be split to pieces and sent
+// in multiple calls to the write function. This can be lowered to reduce RAM usage.
+#define TF_SENDBUF_LEN 1024
+
+// --- Listener counts - determine sizes of the static slot tables ---
+
+// Frame ID listeners (wait for response / multi-part message)
+#define TF_MAX_ID_LST   10
+// Frame Type listeners (wait for frame with a specific first payload byte)
+#define TF_MAX_TYPE_LST 10
+// Generic listeners (fallback if no other listener catches it)
+#define TF_MAX_GEN_LST  1
+
+// Timeout for receiving & parsing a frame
+// ticks = number of calls to TF_Tick()
+#define TF_PARSER_TIMEOUT_TICKS 10
+
+//------------------------- End of user config ------------------------------
+
+#endif //TF_CONFIG_H
diff --git a/gex/protocol/TinyFrame.c b/gex/protocol/TinyFrame.c
new file mode 100644
index 0000000..f165743
--- /dev/null
+++ b/gex/protocol/TinyFrame.c
@@ -0,0 +1,872 @@
+//---------------------------------------------------------------------------
+#include "TinyFrame.h"
+#include <string.h>
+//---------------------------------------------------------------------------
+
+// Compatibility with ESP8266 SDK
+#ifdef ICACHE_FLASH_ATTR
+#define _TF_FN ICACHE_FLASH_ATTR
+#else
+#define _TF_FN
+#endif
+
+// Helper macros
+#define TF_MAX(a, b) ((a)>(b)?(a):(b))
+#define TF_MIN(a, b) ((a)<(b)?(a):(b))
+
+enum TFState {
+	TFState_SOF = 0,      //!< Wait for SOF
+	TFState_LEN,          //!< Wait for Number Of Bytes
+	TFState_HEAD_CKSUM,   //!< Wait for header Checksum
+	TFState_ID,           //!< Wait for ID
+	TFState_TYPE,         //!< Wait for message type
+	TFState_DATA,         //!< Receive payload
+	TFState_DATA_CKSUM    //!< Wait for Checksum
+};
+
+typedef struct _IdListener_struct_ {
+	TF_ID id;
+	TF_Listener fn;
+	TF_TICKS timeout;     // nr of ticks remaining to disable this listener
+	TF_TICKS timeout_max; // the original timeout is stored here
+	void *userdata;
+	void *userdata2;
+} IdListener;
+
+typedef struct _TypeListener_struct_ {
+	TF_TYPE type;
+	TF_Listener fn;
+} TypeListener;
+
+typedef struct _GenericListener_struct_ {
+	TF_Listener fn;
+} GenericListener;
+
+/**
+ * Frame parser internal state
+ */
+static struct TinyFrameStruct {
+	/* Own state */
+	TF_Peer peer_bit;       //!< Own peer bit (unqiue to avoid msg ID clash)
+	TF_ID next_id;          //!< Next frame / frame chain ID
+
+	/* Parser state */
+	enum TFState state;
+	TF_TICKS parser_timeout_ticks;
+	TF_ID id;               //!< Incoming packet ID
+	TF_LEN len;             //!< Payload length
+	uint8_t data[TF_MAX_PAYLOAD_RX]; //!< Data byte buffer
+	TF_LEN rxi;             //!< Field size byte counter
+	TF_CKSUM cksum;         //!< Checksum calculated of the data stream
+	TF_CKSUM ref_cksum;     //!< Reference checksum read from the message
+	TF_TYPE type;           //!< Collected message type number
+	bool discard_data;      //!< Set if (len > TF_MAX_PAYLOAD) to read the frame, but ignore the data.
+
+	/* --- Callbacks --- */
+
+	/* Transaction callbacks */
+	IdListener id_listeners[TF_MAX_ID_LST];
+	TypeListener type_listeners[TF_MAX_TYPE_LST];
+	GenericListener generic_listeners[TF_MAX_GEN_LST];
+
+	// Those counters are used to optimize look-up times.
+	// They point to the highest used slot number,
+	// or close to it, depending on the removal order.
+	TF_COUNT count_id_lst;
+	TF_COUNT count_type_lst;
+	TF_COUNT count_generic_lst;
+
+	// Buffer for building frames
+	uint8_t sendbuf[TF_SENDBUF_LEN];
+} tf;
+
+//region Checksums
+
+#if TF_CKSUM_TYPE == TF_CKSUM_NONE
+
+// NONE
+#define CKSUM_RESET(cksum)
+#define CKSUM_ADD(cksum, byte)
+#define CKSUM_FINALIZE(cksum)
+
+#elif TF_CKSUM_TYPE == TF_CKSUM_XOR
+
+// ~XOR
+#define CKSUM_RESET(cksum) do { (cksum) = 0; } while (0)
+#define CKSUM_ADD(cksum, byte) do { (cksum) ^= (byte); } while(0)
+#define CKSUM_FINALIZE(cksum)  do { (cksum) = (TF_CKSUM)~cksum; } while(0)
+
+#elif TF_CKSUM_TYPE == TF_CKSUM_CRC16
+
+/** CRC table for the CRC-16. The poly is 0x8005 (x^16 + x^15 + x^2 + 1) */
+static const uint16_t crc16_table[256] = {
+	0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
+	0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
+	0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
+	0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
+	0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
+	0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
+	0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
+	0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
+	0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
+	0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
+	0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
+	0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
+	0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
+	0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
+	0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
+	0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
+	0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
+	0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
+	0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
+	0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
+	0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
+	0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
+	0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
+	0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
+	0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
+	0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
+	0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
+	0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
+	0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
+	0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
+	0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
+	0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040
+};
+
+static inline uint16_t crc16_byte(uint16_t cksum, const uint8_t byte)
+{
+	return (cksum >> 8) ^ crc16_table[(cksum ^ byte) & 0xff];
+}
+
+#define CKSUM_RESET(cksum) do { (cksum) = 0; } while (0)
+#define CKSUM_ADD(cksum, byte) do { (cksum) = crc16_byte((cksum), (byte)); } while(0)
+#define CKSUM_FINALIZE(cksum)
+
+#elif TF_CKSUM_TYPE == TF_CKSUM_CRC32
+
+static const uint32_t crc32_table[] = { /* CRC polynomial 0xedb88320 */
+	0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
+	0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
+	0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
+	0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
+	0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
+	0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
+	0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
+	0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
+	0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
+	0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
+	0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
+	0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
+	0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
+	0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
+	0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
+	0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
+	0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
+	0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
+	0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
+	0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
+	0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
+	0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
+	0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
+	0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
+	0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
+	0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
+	0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
+	0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
+	0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
+	0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
+	0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
+	0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
+	0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
+	0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
+	0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
+	0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
+	0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
+	0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
+	0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
+	0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
+	0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
+	0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
+	0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
+};
+
+static inline uint32_t crc32_byte(uint32_t cksum, const uint8_t byte)
+{
+	return (crc32_table[((cksum) ^ ((uint8_t)byte)) & 0xff] ^ ((cksum) >> 8));
+}
+
+#define CKSUM_RESET(cksum) do { (cksum) = (TF_CKSUM)0xFFFFFFFF; } while (0)
+#define CKSUM_ADD(cksum, byte) do { (cksum) = crc32_byte(cksum, byte); } while(0)
+#define CKSUM_FINALIZE(cksum)  do { (cksum) = (TF_CKSUM)~(cksum); } while(0)
+
+#endif
+
+//endregion
+
+
+void _TF_FN TF_Init(TF_Peer peer_bit)
+{
+	// Zero it out
+	memset(&tf, 0, sizeof(struct TinyFrameStruct));
+
+	tf.peer_bit = peer_bit;
+}
+
+//region Listeners
+
+static void _TF_FN renew_id_listener(IdListener *lst)
+{
+	lst->timeout = lst->timeout_max;
+}
+
+/**
+ * Notify callback about ID listener demise & clean it
+ *
+ * @param lst - listener to clean
+ */
+static void _TF_FN cleanup_id_listener(TF_COUNT i, IdListener *lst)
+{
+	TF_Msg msg;
+	if (lst->fn == NULL) return;
+
+	// Make user clean up their data - only if not NULL
+	if (lst->userdata != NULL) {
+		msg.userdata = lst->userdata;
+		msg.userdata2 = lst->userdata2;
+		msg.data = NULL; // this is a signal that the listener should clean up
+		lst->fn(&msg); // return value is ignored here - use TF_STAY or TF_CLOSE
+	}
+
+	lst->fn = NULL; // Discard listener
+
+	if (i == tf.count_id_lst - 1) {
+		tf.count_id_lst--;
+	}
+}
+
+/**
+ * Clean up Type listener
+ *
+ * @param lst - listener to clean
+ */
+static inline void _TF_FN cleanup_type_listener(TF_COUNT i, TypeListener *lst)
+{
+	lst->fn = NULL; // Discard listener
+	if (i == tf.count_type_lst - 1) {
+		tf.count_type_lst--;
+	}
+}
+
+/**
+ * Clean up Generic listener
+ *
+ * @param lst - listener to clean
+ */
+static inline void _TF_FN cleanup_generic_listener(TF_COUNT i, GenericListener *lst)
+{
+	lst->fn = NULL; // Discard listener
+	if (i == tf.count_generic_lst - 1) {
+		tf.count_generic_lst--;
+	}
+}
+
+bool _TF_FN TF_AddIdListener(TF_Msg *msg, TF_Listener cb, TF_TICKS timeout)
+{
+	TF_COUNT i;
+	IdListener *lst;
+	for (i = 0; i < TF_MAX_ID_LST; i++) {
+		lst = &tf.id_listeners[i];
+		// test for empty slot
+		if (lst->fn == NULL) {
+			lst->fn = cb;
+			lst->id = msg->frame_id;
+			lst->userdata = msg->userdata;
+			lst->userdata2 = msg->userdata2;
+			lst->timeout_max = lst->timeout = timeout;
+			if (i >= tf.count_id_lst) {
+				tf.count_id_lst = (TF_COUNT) (i + 1);
+			}
+			return true;
+		}
+	}
+	return false;
+}
+
+bool _TF_FN TF_AddTypeListener(TF_TYPE frame_type, TF_Listener cb)
+{
+	TF_COUNT i;
+	TypeListener *lst;
+	for (i = 0; i < TF_MAX_TYPE_LST; i++) {
+		lst = &tf.type_listeners[i];
+		// test for empty slot
+		if (lst->fn == NULL) {
+			lst->fn = cb;
+			lst->type = frame_type;
+			if (i >= tf.count_type_lst) {
+				tf.count_type_lst = (TF_COUNT) (i + 1);
+			}
+			return true;
+		}
+	}
+	return false;
+}
+
+bool _TF_FN TF_AddGenericListener(TF_Listener cb)
+{
+	TF_COUNT i;
+	GenericListener *lst;
+	for (i = 0; i < TF_MAX_GEN_LST; i++) {
+		lst = &tf.generic_listeners[i];
+		// test for empty slot
+		if (lst->fn == NULL) {
+			lst->fn = cb;
+			if (i >= tf.count_generic_lst) {
+				tf.count_generic_lst = (TF_COUNT) (i + 1);
+			}
+			return true;
+		}
+	}
+	return false;
+}
+
+bool _TF_FN TF_RemoveIdListener(TF_ID frame_id)
+{
+	TF_COUNT i;
+	IdListener *lst;
+	for (i = 0; i < tf.count_id_lst; i++) {
+		lst = &tf.id_listeners[i];
+		// test if live & matching
+		if (lst->fn != NULL && lst->id == frame_id) {
+			cleanup_id_listener(i, lst);
+			return true;
+		}
+	}
+	return false;
+}
+
+bool _TF_FN TF_RemoveTypeListener(TF_TYPE type)
+{
+	TF_COUNT i;
+	TypeListener *lst;
+	for (i = 0; i < tf.count_type_lst; i++) {
+		lst = &tf.type_listeners[i];
+		// test if live & matching
+		if (lst->fn != NULL	&& lst->type == type) {
+			cleanup_type_listener(i, lst);
+			return true;
+		}
+	}
+	return false;
+}
+
+bool _TF_FN TF_RemoveGenericListener(TF_Listener cb)
+{
+	TF_COUNT i;
+	GenericListener *lst;
+	for (i = 0; i < tf.count_generic_lst; i++) {
+		lst = &tf.generic_listeners[i];
+		// test if live & matching
+		if (lst->fn == cb) {
+			cleanup_generic_listener(i, lst);
+			return true;
+		}
+	}
+	return false;
+}
+
+/** Handle a message that was just collected & verified by the parser */
+static void _TF_FN TF_HandleReceivedMessage(void)
+{
+	TF_COUNT i;
+	IdListener *ilst;
+	TypeListener *tlst;
+	GenericListener *glst;
+	TF_Result res;
+
+	// Prepare message object
+	TF_Msg msg;
+	msg.frame_id = tf.id;
+	msg.is_response = false;
+	msg.type = tf.type;
+	msg.data = tf.data;
+	msg.len = tf.len;
+
+	//dumpFrameInfo(&msg);
+
+	// Any listener can consume the message (return true),
+	// or let someone else handle it.
+
+	// The loop upper bounds are the highest currently used slot index
+	// (or close to it, depending on the order of listener removals)
+
+	// ID listeners first
+	for (i = 0; i < tf.count_id_lst; i++) {
+		ilst = &tf.id_listeners[i];
+		if (ilst->fn && ilst->id == msg.frame_id) {
+			msg.userdata = ilst->userdata; // pass userdata pointer to the callback
+			msg.userdata2 = ilst->userdata2;
+			res = ilst->fn(&msg);
+			ilst->userdata = msg.userdata; // put it back (may have changed the pointer or set to NULL)
+			ilst->userdata2 = msg.userdata2; // put it back (may have changed the pointer or set to NULL)
+
+			if (res != TF_NEXT) {
+				if (res == TF_CLOSE) {
+					cleanup_id_listener(i, ilst);
+				}
+				else if (res == TF_RENEW) {
+					renew_id_listener(ilst);
+				}
+				return;
+			}
+		}
+	}
+	msg.userdata = NULL;
+	msg.userdata2 = NULL;
+	// clean up for the following listeners that don't use userdata
+
+	// Type listeners
+	for (i = 0; i < tf.count_type_lst; i++) {
+		tlst = &tf.type_listeners[i];
+		if (tlst->fn && tlst->type == msg.type) {
+			res = tlst->fn(&msg);
+
+			if (res != TF_NEXT) {
+				if (res == TF_CLOSE) {
+					cleanup_type_listener(i, tlst);
+				}
+				return;
+			}
+		}
+	}
+
+	// Generic listeners
+	for (i = 0; i < tf.count_generic_lst; i++) {
+		glst = &tf.generic_listeners[i];
+		if (glst->fn) {
+			res = glst->fn(&msg);
+
+			if (res != TF_NEXT) {
+				if (res == TF_CLOSE) {
+					cleanup_generic_listener(i, glst);
+				}
+				return;
+			}
+		}
+	}
+}
+
+//endregion Listeners
+
+void _TF_FN TF_Accept(const uint8_t *buffer, size_t count)
+{
+	size_t i;
+	for (i = 0; i < count; i++) {
+		TF_AcceptChar(buffer[i]);
+	}
+}
+
+void _TF_FN TF_ResetParser(void)
+{
+	tf.state = TFState_SOF;
+}
+
+/** SOF was received */
+static void _TF_FN TF_ParsBeginFrame(void) {
+	// Reset state vars
+	CKSUM_RESET(tf.cksum);
+#if TF_USE_SOF_BYTE
+	CKSUM_ADD(tf.cksum, TF_SOF_BYTE);
+#endif
+
+	tf.discard_data = false;
+
+	// Enter ID state
+	tf.state = TFState_ID;
+	tf.rxi = 0;
+}
+
+void _TF_FN TF_AcceptChar(unsigned char c)
+{
+	// Parser timeout - clear
+	if (tf.parser_timeout_ticks >= TF_PARSER_TIMEOUT_TICKS) {
+		TF_ResetParser();
+	}
+	tf.parser_timeout_ticks = 0;
+
+// DRY snippet - collect multi-byte number from the input stream
+#define COLLECT_NUMBER(dest, type) dest = (type)(((dest) << 8) | c); \
+								   if (++tf.rxi == sizeof(type))
+
+#if !TF_USE_SOF_BYTE
+	if (tf.state == TFState_SOF) {
+			TF_ParsBeginFrame();
+		}
+#endif
+
+	switch (tf.state) {
+		case TFState_SOF:
+			if (c == TF_SOF_BYTE) {
+				TF_ParsBeginFrame();
+			}
+			break;
+
+		case TFState_ID:
+			CKSUM_ADD(tf.cksum, c);
+			COLLECT_NUMBER(tf.id, TF_ID) {
+				// Enter LEN state
+				tf.state = TFState_LEN;
+				tf.rxi = 0;
+			}
+			break;
+
+		case TFState_LEN:
+			CKSUM_ADD(tf.cksum, c);
+			COLLECT_NUMBER(tf.len, TF_LEN) {
+				// Enter TYPE state
+				tf.state = TFState_TYPE;
+				tf.rxi = 0;
+			}
+			break;
+
+		case TFState_TYPE:
+			CKSUM_ADD(tf.cksum, c);
+			COLLECT_NUMBER(tf.type, TF_TYPE) {
+#if TF_CKSUM_TYPE == TF_CKSUM_NONE
+				tf.state = TFState_DATA;
+				tf.rxi = 0;
+#else
+				// enter HEAD_CKSUM state
+				tf.state = TFState_HEAD_CKSUM;
+				tf.rxi = 0;
+				tf.ref_cksum = 0;
+#endif
+			}
+			break;
+
+		case TFState_HEAD_CKSUM:
+			COLLECT_NUMBER(tf.ref_cksum, TF_CKSUM) {
+				// Check the header checksum against the computed value
+				CKSUM_FINALIZE(tf.cksum);
+
+				if (tf.cksum != tf.ref_cksum) {
+					TF_ResetParser();
+					break;
+				}
+
+				if (tf.len == 0) {
+					TF_HandleReceivedMessage();
+					TF_ResetParser();
+					break;
+				}
+
+				// Enter DATA state
+				tf.state = TFState_DATA;
+				tf.rxi = 0;
+
+				CKSUM_RESET(tf.cksum); // Start collecting the payload
+
+				if (tf.len >= TF_MAX_PAYLOAD_RX) {
+					// ERROR - frame too long. Consume, but do not store.
+					tf.discard_data = true;
+				}
+			}
+			break;
+
+		case TFState_DATA:
+			if (tf.discard_data) {
+				tf.rxi++;
+			} else {
+				CKSUM_ADD(tf.cksum, c);
+				tf.data[tf.rxi++] = c;
+			}
+
+			if (tf.rxi == tf.len) {
+#if TF_CKSUM_TYPE == TF_CKSUM_NONE
+				// All done
+				TF_HandleReceivedMessage();
+				TF_ResetParser();
+#else
+				// Enter DATA_CKSUM state
+				tf.state = TFState_DATA_CKSUM;
+				tf.rxi = 0;
+				tf.ref_cksum = 0;
+#endif
+			}
+			break;
+
+		case TFState_DATA_CKSUM:
+			COLLECT_NUMBER(tf.ref_cksum, TF_CKSUM) {
+				// Check the header checksum against the computed value
+				CKSUM_FINALIZE(tf.cksum);
+				if (!tf.discard_data && tf.cksum == tf.ref_cksum) {
+					TF_HandleReceivedMessage();
+				}
+
+				TF_ResetParser();
+			}
+			break;
+	}
+
+	// we get here after finishing HEAD, if no data are to be received - handle and clear
+	if (tf.len == 0 && tf.state == TFState_DATA) {
+		TF_HandleReceivedMessage();
+		TF_ResetParser();
+	}
+}
+
+// Helper macros for the Compose functions
+// use variables: si - signed int, b - byte, outbuf - target buffer, pos - count of bytes in buffer
+#define WRITENUM_BASE(type, num, xtra) \
+	for (si = sizeof(type)-1; si>=0; si--) { \
+		b = (uint8_t)((num) >> (si*8) & 0xFF); \
+		outbuff[pos++] = b; \
+		xtra; \
+	}
+#define _NOOP()
+#define WRITENUM(type, num)       WRITENUM_BASE(type, num, _NOOP())
+#define WRITENUM_CKSUM(type, num) WRITENUM_BASE(type, num, CKSUM_ADD(cksum, b))
+
+/**
+ * Compose a frame (used internally by TF_Send and TF_Respond).
+ * The frame can be sent using TF_WriteImpl(), or received by TF_Accept()
+ *
+ * @param outbuff - buffer to store the result in
+ * @param msgid - message ID is stored here, if not NULL
+ * @param type - message type
+ * @param len - payload size in bytes
+ * @param explicit_id - ID to use in the frame (8-bit)
+ * @param use_expl_id - whether to use the previous param
+ * @return nr of bytes in outbuff used by the frame, 0 on failure
+ */
+static inline size_t _TF_FN TF_ComposeHead(uint8_t *outbuff, TF_ID *id_ptr,
+									   TF_TYPE type, TF_LEN data_len,
+									   TF_ID explicit_id, bool use_expl_id)
+{
+	int8_t si = 0; // signed small int
+	uint8_t b = 0;
+	TF_ID id = 0;
+	TF_CKSUM cksum = 0;
+	size_t pos = 0; // can be needed to grow larger than TF_LEN
+
+	(void)cksum;
+
+	CKSUM_RESET(cksum);
+
+	// Gen ID
+	if (use_expl_id) {
+		id = explicit_id;
+	}
+	else {
+		id = (TF_ID) (tf.next_id++ & TF_ID_MASK);
+		if (tf.peer_bit) {
+			id |= TF_ID_PEERBIT;
+		}
+	}
+
+	if (id_ptr != NULL) *id_ptr = id;
+
+	// --- Start ---
+	CKSUM_RESET(cksum);
+
+#if TF_USE_SOF_BYTE
+	outbuff[pos++] = TF_SOF_BYTE;
+	CKSUM_ADD(cksum, TF_SOF_BYTE);
+#endif
+
+	WRITENUM_CKSUM(TF_ID, id);
+	WRITENUM_CKSUM(TF_LEN, data_len);
+	WRITENUM_CKSUM(TF_TYPE, type);
+
+#if TF_CKSUM_TYPE != TF_CKSUM_NONE
+	CKSUM_FINALIZE(cksum);
+	WRITENUM(TF_CKSUM, cksum);
+#endif
+
+	return pos;
+}
+
+/**
+ * Compose a frame (used internally by TF_Send and TF_Respond).
+ * The frame can be sent using TF_WriteImpl(), or received by TF_Accept()
+ *
+ * @param outbuff - buffer to store the result in
+ * @param data - data buffer
+ * @param data_len - data buffer len
+ * @param cksum - checksum variable, used for all calls to TF_ComposeBody. Must be reset before first use! (CKSUM_RESET(cksum);)
+ * @return nr of bytes in outbuff used
+ */
+static size_t _TF_FN TF_ComposeBody(uint8_t *outbuff, const uint8_t *data, TF_LEN data_len, TF_CKSUM *cksum)
+{
+	TF_LEN i = 0;
+	uint8_t b = 0;
+	size_t pos = 0;
+
+	for (i = 0; i < data_len; i++) {
+		b = data[i];
+		outbuff[pos++] = b;
+		CKSUM_ADD(*cksum, b);
+	}
+
+	return pos;
+}
+
+/**
+ * Finalize a frame
+ *
+ * @param outbuff - buffer to store the result in
+ * @param cksum - checksum variable used for the body
+ * @return nr of bytes in outbuff used
+ */
+static size_t _TF_FN TF_ComposeTail(uint8_t *outbuff, TF_CKSUM *cksum)
+{
+	int8_t si = 0; // signed small int
+	uint8_t b = 0;
+	size_t pos = 0;
+
+#if TF_CKSUM_TYPE != TF_CKSUM_NONE
+	CKSUM_FINALIZE(*cksum);
+	WRITENUM(TF_CKSUM, *cksum);
+#endif
+	return pos;
+}
+
+// send with listener
+static bool _TF_FN TF_SendFrame(TF_Msg *msg, TF_Listener listener, TF_TICKS timeout)
+{
+	size_t len = 0;
+	size_t remain = 0;
+	size_t sent = 0;
+	TF_CKSUM cksum = 0;
+
+	TF_ClaimTx();
+
+	len = TF_ComposeHead(tf.sendbuf,
+					 &msg->frame_id,
+					 msg->type,
+					 msg->len,
+					 msg->frame_id,
+					 msg->is_response);
+
+	if (listener) TF_AddIdListener(msg, listener, timeout);
+
+	CKSUM_RESET(cksum);
+
+	remain = msg->len;
+	while (remain > 0) {
+		size_t chunk = TF_MIN(TF_SENDBUF_LEN - len, remain);
+		len += TF_ComposeBody(tf.sendbuf+len, msg->data+sent, (TF_LEN) chunk, &cksum);
+		remain -= chunk;
+		sent += chunk;
+
+		// Flush if the buffer is full and we have more to send
+		if (remain > 0 && len == TF_SENDBUF_LEN) {
+			TF_WriteImpl((const uint8_t *) tf.sendbuf, len);
+			len = 0;
+		}
+	}
+
+	// Flush if checksum wouldn't fit in the buffer
+	if (TF_SENDBUF_LEN - len < sizeof(TF_CKSUM)) {
+		TF_WriteImpl((const uint8_t *) tf.sendbuf, len);
+		len = 0;
+	}
+
+	// Add checksum, flush what remains to be sent
+	len += TF_ComposeTail(tf.sendbuf+len, &cksum);
+	TF_WriteImpl((const uint8_t *) tf.sendbuf, len);
+
+	TF_ReleaseTx();
+
+	return true;
+}
+
+// send without listener
+bool _TF_FN TF_Send(TF_Msg *msg)
+{
+	return TF_SendFrame(msg, NULL, 0);
+}
+
+// send without listener and struct
+bool _TF_FN TF_SendSimple(TF_TYPE type, const uint8_t *data, TF_LEN len)
+{
+	TF_Msg msg;
+	TF_ClearMsg(&msg);
+	msg.type = type;
+	msg.data = data;
+	msg.len = len;
+	return TF_Send(&msg);
+}
+
+// send without listener and struct
+bool _TF_FN TF_QuerySimple(TF_TYPE type, const uint8_t *data, TF_LEN len, TF_Listener listener, TF_TICKS timeout, void *userdata)
+{
+	TF_Msg msg;
+	TF_ClearMsg(&msg);
+	msg.type = type;
+	msg.data = data;
+	msg.len = len;
+	msg.userdata = userdata;
+	return TF_SendFrame(&msg, listener, timeout);
+}
+
+// send with listener
+bool _TF_FN TF_Query(TF_Msg *msg, TF_Listener listener, TF_TICKS timeout)
+{
+	return TF_SendFrame(msg, listener, timeout);
+}
+
+// Like TF_Send, but with explicit frame ID
+bool _TF_FN TF_Respond(TF_Msg *msg)
+{
+	msg->is_response = true;
+	return TF_Send(msg);
+}
+
+bool _TF_FN TF_RenewIdListener(TF_ID id)
+{
+	TF_COUNT i;
+	IdListener *lst;
+	for (i = 0; i < tf.count_id_lst; i++) {
+		lst = &tf.id_listeners[i];
+		// test if live & matching
+		if (lst->fn != NULL && lst->id == id) {
+			renew_id_listener(lst);
+			return true;
+		}
+	}
+	return false;
+}
+
+/** Timebase hook - for timeouts */
+void _TF_FN TF_Tick(void)
+{
+	TF_COUNT i = 0;
+	IdListener *lst;
+
+	// increment parser timeout (timeout is handled when receiving next byte)
+	if (tf.parser_timeout_ticks < TF_PARSER_TIMEOUT_TICKS) {
+		tf.parser_timeout_ticks++;
+	}
+
+	// decrement and expire ID listeners
+	for (i = 0; i < tf.count_id_lst; i++) {
+		lst = &tf.id_listeners[i];
+		if (!lst->fn || lst->timeout == 0) continue;
+		// count down...
+		if (--lst->timeout == 0) {
+			// Listener has expired
+			cleanup_id_listener(i, lst);
+		}
+	}
+}
+
+void __attribute__((weak)) TF_ClaimTx(void)
+{
+	// do nothing
+}
+
+void __attribute__((weak)) TF_ReleaseTx(void)
+{
+	// do nothing
+}
diff --git a/gex/protocol/TinyFrame.h b/gex/protocol/TinyFrame.h
new file mode 100644
index 0000000..3dc9372
--- /dev/null
+++ b/gex/protocol/TinyFrame.h
@@ -0,0 +1,280 @@
+#ifndef TinyFrameH
+#define TinyFrameH
+
+/**
+ * TinyFrame protocol library
+ * 
+ * (c) Ondřej Hruška 2017, MIT License 
+ * no liability/warranty, free for any use, must retain this notice & license
+ * 
+ * Upstream URL: https://github.com/MightyPork/TinyFrame
+ */
+
+#define TF_VERSION "1.2.0"
+
+//---------------------------------------------------------------------------
+#include <stdint.h>  // for uint8_t etc
+#include <stdbool.h> // for bool
+#include <stdlib.h>  // for NULL
+//---------------------------------------------------------------------------
+
+// Select checksum type (0 = none, 8 = ~XOR, 16 = CRC16 0x8005, 32 = CRC32)
+#define TF_CKSUM_NONE  0
+#define TF_CKSUM_XOR   8
+#define TF_CKSUM_CRC16 16
+#define TF_CKSUM_CRC32 32
+
+#include <TF_Config.h>
+
+//region Resolve data types
+
+#if TF_LEN_BYTES == 1
+	typedef uint8_t TF_LEN;
+#elif TF_LEN_BYTES == 2
+	typedef uint16_t TF_LEN;
+#elif TF_LEN_BYTES == 4
+	typedef uint32_t TF_LEN;
+#else
+	#error Bad value of TF_LEN_BYTES, must be 1, 2 or 4
+#endif
+
+
+#if TF_TYPE_BYTES == 1
+	typedef uint8_t TF_TYPE;
+#elif TF_TYPE_BYTES == 2
+	typedef uint16_t TF_TYPE;
+#elif TF_TYPE_BYTES == 4
+	typedef uint32_t TF_TYPE;
+#else
+	#error Bad value of TF_TYPE_BYTES, must be 1, 2 or 4
+#endif
+
+
+#if TF_ID_BYTES == 1
+	typedef uint8_t TF_ID;
+#elif TF_ID_BYTES == 2
+	typedef uint16_t TF_ID;
+#elif TF_ID_BYTES == 4
+	typedef uint32_t TF_ID;
+#else
+	#error Bad value of TF_ID_BYTES, must be 1, 2 or 4
+#endif
+
+
+#if TF_CKSUM_TYPE == TF_CKSUM_XOR || TF_CKSUM_TYPE == TF_CKSUM_NONE
+	// ~XOR (if 0, still use 1 byte - it won't be used)
+	typedef uint8_t TF_CKSUM;
+#elif TF_CKSUM_TYPE == TF_CKSUM_CRC16
+	// CRC16
+	typedef uint16_t TF_CKSUM;
+#elif TF_CKSUM_TYPE == TF_CKSUM_CRC32
+	// CRC32
+	typedef uint32_t TF_CKSUM;
+#else
+	#error Bad value for TF_CKSUM_TYPE, must be 8, 16 or 32
+#endif
+
+//endregion
+
+//---------------------------------------------------------------------------
+
+// Type-dependent masks for bit manipulation in the ID field
+#define TF_ID_MASK (TF_ID)(((TF_ID)1 << (sizeof(TF_ID)*8 - 1)) - 1)
+#define TF_ID_PEERBIT (TF_ID)((TF_ID)1 << ((sizeof(TF_ID)*8) - 1))
+
+//---------------------------------------------------------------------------
+
+/** Peer bit enum (used for init) */
+typedef enum {
+	TF_SLAVE = 0,
+	TF_MASTER,
+} TF_Peer;
+
+typedef enum {
+	TF_NEXT = 0,   //!< Not handled, let other listeners handle it
+	TF_STAY = 1,   //!< Handled, stay
+	TF_RENEW = 2,  //!< Handled, stay, renew - useful only with listener timeout
+	TF_CLOSE = 3,  //!< Handled, remove self
+} TF_Result;
+
+/** Data structure for sending / receiving messages */
+typedef struct _TF_MSG_STRUCT_ {
+	TF_ID frame_id;       //!< message ID
+	bool is_response;     //!< internal flag, set when using the Respond function. frame_id is then kept unchanged.
+	TF_TYPE type;         //!< received or sent message type
+	const uint8_t *data;  //!< buffer of received data or data to send. NULL = listener timed out, free userdata!
+	TF_LEN len;           //!< length of the buffer
+	void *userdata;       //!< here's a place for custom data; this data will be stored with the listener
+	void *userdata2;
+} TF_Msg;
+
+/**
+ * Clear message struct
+ */
+static inline void TF_ClearMsg(TF_Msg *msg)
+{
+	msg->frame_id = 0;
+	msg->is_response = false;
+	msg->type = 0;
+	msg->data = NULL;
+	msg->len = 0;
+	msg->userdata = NULL;
+	msg->userdata2 = NULL;
+}
+
+/**
+ * TinyFrame Type Listener callback
+ *
+ * @param frame_id - ID of the received frame
+ * @param type - type field from the message
+ * @param data - byte buffer with the application data
+ * @param len - number of bytes in the buffer
+ * @return listener result
+ */
+typedef TF_Result (*TF_Listener)(TF_Msg *msg);
+
+/**
+ * Initialize the TinyFrame engine.
+ * This can also be used to completely reset it (removing all listeners etc)
+ *
+ * @param peer_bit - peer bit to use for self
+ */
+void TF_Init(TF_Peer peer_bit);
+
+/**
+ * Reset the frame parser state machine.
+ * This does not affect registered listeners.
+ */
+void TF_ResetParser(void);
+
+/**
+ * Register a frame type listener.
+ *
+ * @param msg - message (contains frame_id and userdata)
+ * @param cb - callback
+ * @param timeout - timeout in ticks to auto-remove the listener (0 = keep forever)
+ * @return slot index (for removing), or TF_ERROR (-1)
+ */
+bool TF_AddIdListener(TF_Msg *msg, TF_Listener cb, TF_TICKS timeout);
+
+/**
+ * Remove a listener by the message ID it's registered for
+ *
+ * @param frame_id - the frame we're listening for
+ */
+bool TF_RemoveIdListener(TF_ID frame_id);
+
+/**
+ * Register a frame type listener.
+ *
+ * @param frame_type - frame type to listen for
+ * @param cb - callback
+ * @return slot index (for removing), or TF_ERROR (-1)
+ */
+bool TF_AddTypeListener(TF_TYPE frame_type, TF_Listener cb);
+
+/**
+ * Remove a listener by type.
+ *
+ * @param type - the type it's registered for
+ */
+bool TF_RemoveTypeListener(TF_TYPE type);
+
+/**
+ * Register a generic listener.
+ *
+ * @param cb - callback
+ * @return slot index (for removing), or TF_ERROR (-1)
+ */
+bool TF_AddGenericListener(TF_Listener cb);
+
+/**
+ * Remove a generic listener by function pointer
+ *
+ * @param cb - callback function to remove
+ */
+bool TF_RemoveGenericListener(TF_Listener cb);
+
+/**
+ * Send a frame, no listener
+ *
+ * @param msg - message struct. ID is stored in the frame_id field
+ * @return success
+ */
+bool TF_Send(TF_Msg *msg);
+
+/**
+ * Like TF_Send, but without the struct
+ */
+bool TF_SendSimple(TF_TYPE type, const uint8_t *data, TF_LEN len);
+
+/**
+ * Like TF_Query, but without the struct
+ */
+bool TF_QuerySimple(TF_TYPE type, const uint8_t *data, TF_LEN len, TF_Listener listener, TF_TICKS timeout, void *userdata);
+
+/**
+ * Send a frame, and optionally attach an ID listener.
+ *
+ * @param msg - message struct. ID is stored in the frame_id field
+ * @param listener - listener waiting for the response (can be NULL)
+ * @param timeout - listener expiry time in ticks
+ * @return success
+ */
+bool TF_Query(TF_Msg *msg, TF_Listener listener, TF_TICKS timeout);
+
+/**
+ * Send a response to a received message.
+ *
+ * @param msg - message struct. ID is read from frame_id. set ->renew to reset listener timeout
+ * @return success
+ */
+bool TF_Respond(TF_Msg *msg);
+
+/**
+ * Renew ID listener timeout
+ *
+ * @param id - listener ID to renew
+ * @return true if listener was found and renewed
+ */
+bool TF_RenewIdListener(TF_ID id);
+
+/**
+ * Accept incoming bytes & parse frames
+ *
+ * @param buffer - byte buffer to process
+ * @param count - nr of bytes in the buffer
+ */
+void TF_Accept(const uint8_t *buffer, size_t count);
+
+/**
+ * Accept a single incoming byte
+ *
+ * @param c - a received char
+ */
+void TF_AcceptChar(uint8_t c);
+
+/**
+ * 'Write bytes' function that sends data to UART
+ *
+ * ! Implement this in your application code !
+ */
+extern void TF_WriteImpl(const uint8_t *buff, size_t len);
+
+/**
+ * This function should be called periodically.
+ *
+ * The time base is used to time-out partial frames in the parser and
+ * automatically reset it.
+ *
+ * (suggestion - call this in a SysTick handler)
+ */
+void TF_Tick(void);
+
+/** Claim the TX interface before composing and sending a frame */
+extern void TF_ClaimTx(void);
+
+/** Free the TX interface after composing and sending a frame */
+extern void TF_ReleaseTx(void);
+
+#endif
diff --git a/gex/protocol/payload_builder.c b/gex/protocol/payload_builder.c
new file mode 100644
index 0000000..d228d80
--- /dev/null
+++ b/gex/protocol/payload_builder.c
@@ -0,0 +1,100 @@
+#include <string.h>
+#include "payload_builder.h"
+
+#define pb_check_capacity(pb, needed) \
+    if ((pb)->current + (needed) > (pb)->end) { \
+        if ((pb)->full_handler == NULL || !(pb)->full_handler(pb, needed)) (pb)->ok = 0; \
+    }
+
+/** Write from a buffer */
+bool pb_buf(PayloadBuilder *pb, const uint8_t *buf, uint32_t len)
+{
+    pb_check_capacity(pb, len);
+    if (!pb->ok) return false;
+
+    memcpy(pb->current, buf, len);
+    pb->current += len;
+    return true;
+}
+
+/** Write s zero terminated string */
+bool pb_string(PayloadBuilder *pb, const char *str)
+{
+    uint32_t len = (uint32_t) strlen(str);
+    pb_check_capacity(pb, len+1);
+    if (!pb->ok) return false;
+
+    memcpy(pb->current, str, len+1);
+    pb->current += len+1;
+    return true;
+}
+
+/** Write uint8_t to the buffer */
+bool pb_u8(PayloadBuilder *pb, uint8_t byte)
+{
+    pb_check_capacity(pb, 1);
+    if (!pb->ok) return false;
+
+    *pb->current++ = byte;
+    return true;
+}
+
+/** Write uint16_t to the buffer. */
+bool pb_u16(PayloadBuilder *pb, uint16_t word)
+{
+    pb_check_capacity(pb, 2);
+    if (!pb->ok) return false;
+
+    if (pb->bigendian) {
+        *pb->current++ = (uint8_t) ((word >> 8) & 0xFF);
+        *pb->current++ = (uint8_t) (word & 0xFF);
+    } else {
+        *pb->current++ = (uint8_t) (word & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 8) & 0xFF);
+    }
+    return true;
+}
+
+/** Write uint32_t to the buffer. */
+bool pb_u32(PayloadBuilder *pb, uint32_t word)
+{
+    pb_check_capacity(pb, 4);
+    if (!pb->ok) return false;
+
+    if (pb->bigendian) {
+        *pb->current++ = (uint8_t) ((word >> 24) & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 16) & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 8) & 0xFF);
+        *pb->current++ = (uint8_t) (word & 0xFF);
+    } else {
+        *pb->current++ = (uint8_t) (word & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 8) & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 16) & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 24) & 0xFF);
+    }
+    return true;
+}
+
+/** Write int8_t to the buffer. */
+bool pb_i8(PayloadBuilder *pb, int8_t byte)
+{
+    return pb_u8(pb, ((union conv8){.i8 = byte}).u8);
+}
+
+/** Write int16_t to the buffer. */
+bool pb_i16(PayloadBuilder *pb, int16_t word)
+{
+    return pb_u16(pb, ((union conv16){.i16 = word}).u16);
+}
+
+/** Write int32_t to the buffer. */
+bool pb_i32(PayloadBuilder *pb, int32_t word)
+{
+    return pb_u32(pb, ((union conv32){.i32 = word}).u32);
+}
+
+/** Write 4-byte float to the buffer. */
+bool pb_float(PayloadBuilder *pb, float f)
+{
+    return pb_u32(pb, ((union conv32){.f32 = f}).u32);
+}
diff --git a/gex/protocol/payload_builder.h b/gex/protocol/payload_builder.h
new file mode 100644
index 0000000..e4d6568
--- /dev/null
+++ b/gex/protocol/payload_builder.h
@@ -0,0 +1,110 @@
+#ifndef PAYLOAD_BUILDER_H
+#define PAYLOAD_BUILDER_H
+
+/**
+ * PayloadBuilder, part of the TinyFrame utilities collection
+ * 
+ * (c) Ondřej Hruška, 2014-2017. MIT license.
+ * 
+ * The builder supports big and little endian which is selected when 
+ * initializing it or by accessing the bigendian struct field.
+ * 
+ * This module helps you with building payloads (not only for TinyFrame)
+ *
+ * The builder performs bounds checking and calls the provided handler when 
+ * the requested write wouldn't fit. Use the handler to realloc / flush the buffer
+ * or report an error.
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include "type_coerce.h"
+
+typedef struct PayloadBuilder_ PayloadBuilder;
+
+/**
+ * Full buffer handler. 
+ * 
+ * 'needed' more bytes should be written but the end of the buffer was reached.
+ * 
+ * Return true if the problem was solved (e.g. buffer was flushed and the 
+ * 'current' pointer moved to the beginning).
+ * 
+ * If false is returned, the 'ok' flag on the struct is set to false
+ * and all following writes are discarded.
+ */
+typedef bool (*pb_full_handler)(PayloadBuilder *pb, uint32_t needed);
+
+struct PayloadBuilder_ {
+    uint8_t *start;   //!< Pointer to the beginning of the buffer
+    uint8_t *current; //!< Pointer to the next byte to be read
+    uint8_t *end;     //!< Pointer to the end of the buffer (start + length)
+    pb_full_handler full_handler; //!< Callback for buffer overrun
+    bool bigendian;   //!< Flag to use big-endian parsing
+    bool ok;          //!< Indicates that all reads were successful
+};
+
+// --- initializer helper macros ---
+
+/** Start the builder. */
+#define pb_start_e(buf, capacity, bigendian, full_handler) ((PayloadBuilder){buf, buf, (buf)+(capacity), full_handler, bigendian, 1})
+
+/** Start the builder in big-endian mode */
+#define pb_start_be(buf, capacity, full_handler) pb_start_e(buf, capacity, 1, full_handler)
+
+/** Start the builder in little-endian mode */
+#define pb_start_le(buf, capacity, full_handler) pb_start_e(buf, capacity, 0, full_handler)
+
+/** Start the parser in little-endian mode (default) */
+#define pb_start(buf, capacity, full_handler) pb_start_le(buf, capacity, full_handler)
+
+// --- utilities ---
+
+/** Get already used bytes count */
+#define pb_length(pb) ((pb)->current - (pb)->start)
+
+/** Reset the current pointer to start */
+#define pb_rewind(pb) do { pb->current = pb->start; } while (0)
+
+
+/** Write from a buffer */
+bool pb_buf(PayloadBuilder *pb, const uint8_t *buf, uint32_t len);
+
+/** Write a zero terminated string */
+bool pb_string(PayloadBuilder *pb, const char *str);
+
+/** Write uint8_t to the buffer */
+bool pb_u8(PayloadBuilder *pb, uint8_t byte);
+
+/** Write boolean to the buffer. */
+static inline bool pb_bool(PayloadBuilder *pb, bool b)
+{
+    return pb_u8(pb, (uint8_t) b);
+}
+
+/** Write uint16_t to the buffer. */
+bool pb_u16(PayloadBuilder *pb, uint16_t word);
+
+/** Write uint32_t to the buffer. */
+bool pb_u32(PayloadBuilder *pb, uint32_t word);
+
+/** Write int8_t to the buffer. */
+bool pb_i8(PayloadBuilder *pb, int8_t byte);
+
+/** Write char (int8_t) to the buffer. */
+static inline bool pb_char(PayloadBuilder *pb, char c)
+{
+    return pb_i8(pb, c);
+}
+
+/** Write int16_t to the buffer. */
+bool pb_i16(PayloadBuilder *pb, int16_t word);
+
+/** Write int32_t to the buffer. */
+bool pb_i32(PayloadBuilder *pb, int32_t word);
+
+/** Write 4-byte float to the buffer. */
+bool pb_float(PayloadBuilder *pb, float f);
+
+#endif // PAYLOAD_BUILDER_H
diff --git a/gex/protocol/payload_parser.c b/gex/protocol/payload_parser.c
new file mode 100644
index 0000000..ca80605
--- /dev/null
+++ b/gex/protocol/payload_parser.c
@@ -0,0 +1,121 @@
+#include "payload_parser.h"
+
+#define pp_check_capacity(pp, needed) \
+    if ((pp)->current + (needed) > (pp)->end) { \
+        if ((pp)->empty_handler == NULL || !(pp)->empty_handler(pp, needed)) {(pp)->ok = 0;} ; \
+    }
+
+void pp_skip(PayloadParser *pp, uint32_t num)
+{
+    pp->current += num;
+}
+
+uint8_t pp_u8(PayloadParser *pp)
+{
+    pp_check_capacity(pp, 1);
+    if (!pp->ok) return 0;
+
+    return *pp->current++;
+}
+
+uint16_t pp_u16(PayloadParser *pp)
+{
+    pp_check_capacity(pp, 2);
+    if (!pp->ok) return 0;
+
+    uint16_t x = 0;
+
+    if (pp->bigendian) {
+        x |= *pp->current++ << 8;
+        x |= *pp->current++;
+    } else {
+        x |= *pp->current++;
+        x |= *pp->current++ << 8;
+    }
+    return x;
+}
+
+uint32_t pp_u32(PayloadParser *pp)
+{
+    pp_check_capacity(pp, 4);
+    if (!pp->ok) return 0;
+
+    uint32_t x = 0;
+
+    if (pp->bigendian) {
+        x |= (uint32_t) (*pp->current++ << 24);
+        x |= (uint32_t) (*pp->current++ << 16);
+        x |= (uint32_t) (*pp->current++ << 8);
+        x |= *pp->current++;
+    } else {
+        x |= *pp->current++;
+        x |= (uint32_t) (*pp->current++ << 8);
+        x |= (uint32_t) (*pp->current++ << 16);
+        x |= (uint32_t) (*pp->current++ << 24);
+    }
+    return x;
+}
+
+const uint8_t *pp_tail(PayloadParser *pp, uint32_t *length)
+{
+    int32_t len = (int) (pp->end - pp->current);
+    if (!pp->ok || len <= 0) {
+        if (length != NULL) *length = 0;
+        return NULL;
+    }
+
+    if (length != NULL) {
+        *length = (uint32_t) len;
+    }
+
+    return pp->current;
+}
+
+/** Read int8_t from the payload. */
+int8_t pp_i8(PayloadParser *pp)
+{
+    return ((union conv8) {.u8 = pp_u8(pp)}).i8;
+}
+
+/** Read int16_t from the payload. */
+int16_t pp_i16(PayloadParser *pp)
+{
+    return ((union conv16) {.u16 = pp_u16(pp)}).i16;
+}
+
+/** Read int32_t from the payload. */
+int32_t pp_i32(PayloadParser *pp)
+{
+    return ((union conv32) {.u32 = pp_u32(pp)}).i32;
+}
+
+/** Read 4-byte float from the payload. */
+float pp_float(PayloadParser *pp)
+{
+    return ((union conv32) {.u32 = pp_u32(pp)}).f32;
+}
+
+/** Read a zstring */
+uint32_t pp_string(PayloadParser *pp, char *buffer, uint32_t maxlen)
+{
+    pp_check_capacity(pp, 1);
+    uint32_t len = 0;
+    while (len < maxlen-1 && pp->current != pp->end) {
+        char c = *buffer++ = *pp->current++;
+        if (c == 0) break;
+        len++;
+    }
+    *buffer = 0;
+    return len;
+}
+
+/** Read a buffer */
+uint32_t pp_buf(PayloadParser *pp, uint8_t *buffer, uint32_t maxlen)
+{
+    uint32_t len = 0;
+    while (len < maxlen && pp->current != pp->end) {
+        *buffer++ = *pp->current++;
+        len++;
+    }
+    return len;
+}
diff --git a/gex/protocol/payload_parser.h b/gex/protocol/payload_parser.h
new file mode 100644
index 0000000..cddab1b
--- /dev/null
+++ b/gex/protocol/payload_parser.h
@@ -0,0 +1,143 @@
+#ifndef PAYLOAD_PARSER_H
+#define PAYLOAD_PARSER_H
+
+/**
+ * PayloadParser, part of the TinyFrame utilities collection
+ * 
+ * (c) Ondřej Hruška, 2016-2017. MIT license.
+ * 
+ * This module helps you with parsing payloads (not only from TinyFrame).
+ * 
+ * The parser supports big and little-endian which is selected when 
+ * initializing it or by accessing the bigendian struct field.
+ *
+ * The parser performs bounds checking and calls the provided handler when 
+ * the requested read doesn't have enough data. Use the callback to take
+ * appropriate action, e.g. report an error.
+ * 
+ * If the handler function is not defined, the pb->ok flag is set to false
+ * (use this to check for success), and further reads won't have any effect 
+ * and always result in 0 or empty array.
+ */
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include "type_coerce.h"
+
+typedef struct PayloadParser_ PayloadParser;
+
+/**
+ * Empty buffer handler. 
+ * 
+ * 'needed' more bytes should be read but the end was reached.
+ * 
+ * Return true if the problem was solved (e.g. new data loaded into 
+ * the buffer and the 'current' pointer moved to the beginning).
+ *  
+ * If false is returned, the 'ok' flag on the struct is set to false
+ * and all following reads will fail / return 0.
+ */
+typedef bool (*pp_empty_handler)(PayloadParser *pp, uint32_t needed);
+
+struct PayloadParser_ {
+    uint8_t *start;   //!< Pointer to the beginning of the buffer
+    uint8_t *current; //!< Pointer to the next byte to be read
+    uint8_t *end;     //!< Pointer to the end of the buffer (start + length)
+    pp_empty_handler empty_handler; //!< Callback for buffer underrun
+    bool bigendian;   //!< Flag to use big-endian parsing
+    bool ok;          //!< Indicates that all reads were successful
+};
+
+// --- initializer helper macros ---
+
+/** Start the parser. */
+#define pp_start_e(buf, length, bigendian, empty_handler) ((PayloadParser){buf, buf, (buf)+(length), empty_handler, bigendian, 1})
+
+/** Start the parser in big-endian mode */
+#define pp_start_be(buf, length, empty_handler) pp_start_e(buf, length, 1, empty_handler)
+
+/** Start the parser in little-endian mode */
+#define pp_start_le(buf, length, empty_handler) pp_start_e(buf, length, 0, empty_handler)
+
+/** Start the parser in little-endian mode (default) */
+#define pp_start(buf, length, empty_handler) pp_start_le(buf, length, empty_handler)
+
+// --- utilities ---
+
+/** Get remaining length */
+#define pp_length(pp) ((pp)->end - (pp)->current)
+
+/** Reset the current pointer to start */
+#define pp_rewind(pp) do { pp->current = pp->start; } while (0)
+
+
+/**
+ * @brief Get the remainder of the buffer.
+ *
+ * Returns NULL and sets 'length' to 0 if there are no bytes left.
+ *
+ * @param pp
+ * @param length : here the buffer length will be stored. NULL to do not store.
+ * @return the remaining portion of the input buffer
+ */
+const uint8_t *pp_tail(PayloadParser *pp, uint32_t *length);
+
+/** Read uint8_t from the payload. */
+uint8_t pp_u8(PayloadParser *pp);
+
+/** Read bool from the payload. */
+static inline int8_t pp_bool(PayloadParser *pp)
+{
+    return pp_u8(pp) != 0;
+}
+
+/** Skip bytes */
+void pp_skip(PayloadParser *pp, uint32_t num);
+
+/** Read uint16_t from the payload. */
+uint16_t pp_u16(PayloadParser *pp);
+
+/** Read uint32_t from the payload. */
+uint32_t pp_u32(PayloadParser *pp);
+
+/** Read int8_t from the payload. */
+int8_t pp_i8(PayloadParser *pp);
+
+/** Read char (int8_t) from the payload. */
+static inline int8_t pp_char(PayloadParser *pp)
+{
+    return pp_i8(pp);
+}
+
+/** Read int16_t from the payload. */
+int16_t pp_i16(PayloadParser *pp);
+
+/** Read int32_t from the payload. */
+int32_t pp_i32(PayloadParser *pp);
+
+/** Read 4-byte float from the payload. */
+float pp_float(PayloadParser *pp);
+
+/**
+ * Parse a zero-terminated string
+ *
+ * @param pp - parser
+ * @param buffer - target buffer
+ * @param maxlen - buffer size
+ * @return actual number of bytes, excluding terminator
+ */
+uint32_t pp_string(PayloadParser *pp, char *buffer, uint32_t maxlen);
+
+/**
+ * Parse a buffer
+ *
+ * @param pp - parser
+ * @param buffer - target buffer
+ * @param maxlen - buffer size
+ * @return actual number of bytes, excluding terminator
+ */
+uint32_t pp_buf(PayloadParser *pp, uint8_t *buffer, uint32_t maxlen);
+
+
+#endif // PAYLOAD_PARSER_H
diff --git a/gex/protocol/type_coerce.h b/gex/protocol/type_coerce.h
new file mode 100644
index 0000000..2e4d0c6
--- /dev/null
+++ b/gex/protocol/type_coerce.h
@@ -0,0 +1,32 @@
+#ifndef TYPE_COERCE_H
+#define TYPE_COERCE_H
+
+/**
+ * Structs for conversion between types,
+ * part of the TinyFrame utilities collection
+ * 
+ * (c) Ondřej Hruška, 2016-2017. MIT license.
+ * 
+ * This is a support header file for PayloadParser and PayloadBuilder.
+ */
+
+#include <stdint.h>
+#include <stddef.h>
+
+union conv8 {
+    uint8_t u8;
+    int8_t i8;
+};
+
+union conv16 {
+    uint16_t u16;
+    int16_t i16;
+};
+
+union conv32 {
+    uint32_t u32;
+    int32_t i32;
+    float f32;
+};
+
+#endif // TYPE_COERCE_H
diff --git a/gex/serial/serial.c b/gex/serial/serial.c
new file mode 100644
index 0000000..d53d5fa
--- /dev/null
+++ b/gex/serial/serial.c
@@ -0,0 +1,77 @@
+#include "serial.h"
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <termios.h>
+#include <unistd.h>
+
+static int set_interface_attribs(int fd, int speed, int parity)
+{
+	struct termios tty;
+	memset(&tty, 0, sizeof tty);
+	if (tcgetattr(fd, &tty) != 0) {
+		printf("error %d from tcgetattr\n", errno);
+		return -1;
+	}
+
+	cfsetospeed(&tty, (speed_t) speed);
+	cfsetispeed(&tty, (speed_t) speed);
+
+	tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8;     // 8-bit chars
+	// disable IGNBRK for mismatched speed tests; otherwise receive break
+	// as \000 chars
+	tty.c_iflag &= ~IGNBRK;         // disable break processing
+	tty.c_lflag = 0;                // no signaling chars, no echo,
+	// no canonical processing
+	tty.c_oflag = 0;                // no remapping, no delays
+	tty.c_cc[VMIN] = 0;            // read doesn't block
+	tty.c_cc[VTIME] = 5;            // 0.5 seconds read timeout
+
+	tty.c_iflag &= ~(IXON | IXOFF | IXANY); // shut off xon/xoff ctrl
+
+	tty.c_cflag |= (CLOCAL | CREAD);// ignore modem controls,
+	// enable reading
+	tty.c_cflag &= ~(PARENB | PARODD);      // shut off parity
+	tty.c_cflag |= parity;
+	tty.c_cflag &= ~CSTOPB;
+	tty.c_cflag &= ~CRTSCTS;
+
+	if (tcsetattr(fd, TCSANOW, &tty) != 0) {
+		printf("error %d from tcsetattr\n", errno);
+		return -1;
+	}
+	return 0;
+}
+
+static void set_blocking(int fd, bool should_block, int read_timeout_0s1)
+{
+	struct termios tty;
+	memset(&tty, 0, sizeof tty);
+	if (tcgetattr(fd, &tty) != 0) {
+		fprintf(stderr, "error %d from tggetattr\n", errno);
+		return;
+	}
+
+	tty.c_cc[VMIN] = (cc_t) (should_block ? 1 : 0);
+	tty.c_cc[VTIME] = (cc_t) read_timeout_0s1;
+
+	if (tcsetattr(fd, TCSANOW, &tty) != 0)
+		fprintf(stderr, "error %d setting term attributes\n", errno);
+}
+
+int serial_open(const char *device, bool blocking, int timeout_0s1)
+{
+	int fd = open (device, O_RDWR | O_NOCTTY | O_SYNC);
+	if (fd < 0) {
+		fprintf (stderr, "FAILED TO OPEN SERIAL! Error %d opening %s: %s\n", errno, device, strerror (errno));
+		return -1;
+	}
+
+	set_interface_attribs(fd, B115200, 0);
+	set_blocking (fd, blocking, timeout_0s1);
+
+	return fd;
+}
diff --git a/gex/serial/serial.h b/gex/serial/serial.h
new file mode 100644
index 0000000..992c58a
--- /dev/null
+++ b/gex/serial/serial.h
@@ -0,0 +1,17 @@
+#ifndef SERIAL_H
+#define SERIAL_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+/**
+ * Open a serial port
+ *
+ * @param device - device to open, e.g. /dev/ttyACM0
+ * @param blocking - true for `read()` to block until at least 1 byte is read
+ * @param timeout_0s1 - timeout for `read()` - if blocking, starts after the first character
+ * @return file descriptor
+ */
+int serial_open(const char *device, bool blocking, int timeout_0s1);
+
+#endif
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..a4e2f6a
--- /dev/null
+++ b/main.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "gex_client.h"
+
+int main()
+{
+	GexClient *gex = GEX_Init("/dev/ttyACM0", 200);
+	if (!gex) {
+		fprintf(stderr, "FAILED TO CONNECT, ABORTING!\n");
+		exit(1);
+	}
+
+	printf("Hello, World!\n");
+
+	GEX_DeInit(gex);
+	return 0;
+}