api/shellmatta.h

@@ -110,7 +110,7 @@ typedef struct shellmatta_cmd
     char                    *cmdAlias;  /**< command alias                          */
     char                    *helpText;  /**< help text to print in "help" command   */
     char                    *usageText; /**< usage text - printed on "help cmd"     */
-    shellmatta_cmdFct_t     cmdFct;     /**< pointer to the cmd callack function    */
+    shellmatta_cmdFct_t     cmdFct;     /**< pointer to the cmd callback function   */
     struct shellmatta_cmd   *next;      /**< pointer to next command or NULL        */
 } shellmatta_cmd_t;
 

doc/shellmatta_transport_layer.dox

@@ -32,18 +32,18 @@
     @section shellmatta_transport_layer_protocol Protocol
 
 
-    | Offset | Length   | Description                                 |
-    |--------|----------|---------------------------------------------|
-    |    0   |     1    | Start of header (\SOH)                      |
-    |    1   |     1    | Protocol version                            |
-    |    2   |     1    | Packet type                                 |
-    |    3   |     1    | Payload Length                              |
-    |    4   |     1    | Source                                      |
-    |    5   |     1    | Destination                                 |
-    |    6   |     1    | Sequence counter host to shellmatta         |
-    |    7   |     1    | Sequence counter shellmatta to host         |
-    |    8   |     4    | CRC32 of header + payload without CRC32     |
-    |    12  | 0 .. 255 | Payload                                     |
+    | Offset | Length        | Description                                 |
+    |--------|---------------|---------------------------------------------|
+    |    0   |     1         | Start of header (\\SOH)                     |
+    |    1   |     1         | Protocol version                            |
+    |    2   |     1         | Packet type                                 |
+    |    3   |     1         | Payload Length                              |
+    |    4   |     1         | Source                                      |
+    |    5   |     1         | Destination                                 |
+    |    6   |     1         | Sequence counter host to shellmatta         |
+    |    7   |     1         | Sequence counter shellmatta to host         |
+    |    8   | L1 = 0 .. 255 | Payload                                     |
+    |8 + L1  |     4         | CRC32 of header + payload without CRC32     |
 
 
     @subsection shellmatta_transport_layer_protocol_packet_Types Packet types

makefile

@@ -20,7 +20,9 @@ SOURCES :=  src/shellmatta.c                \
             src/shellmatta_history.c        \
             src/shellmatta_utils.c          \
             src/shellmatta_escape.c         \
-            src/shellmatta_opt.c
+            src/shellmatta_opt.c            \
+            src/shellmatta_transport.c      \
+            src/shellmatta_crc.c
 
 INCLUDES    := api .
 

src/shellmatta.c

@@ -23,6 +23,7 @@
 #include "shellmatta_utils.h"
 #include "shellmatta_escape.h"
 #include "shellmatta_opt.h"
+#include "shellmatta_transport.h"
 #include <stddef.h>
 #include <string.h>
 #include <stdarg.h>
@@ -117,6 +118,10 @@ shellmatta_retCode_t shellmatta_doInit(
 
         /** -# print the first prompt */
         utils_terminateInput(inst);
+
+        /* init transport layer */
+        shellmatta_init_transport_inst();
+        transportLayerInst.originalWrite = inst->write;
     }
 
     return SHELLMATTA_OK;
@@ -382,6 +387,106 @@ shellmatta_retCode_t shellmatta_processData(shellmatta_handle_t     handle,
     if(     (NULL               != inst)
         &&  (SHELLMATTA_MAGIC   == inst->magic))
     {
+        if (    (transportLayerInst.state != STATE_PROCESS_PAYLOAD)
+            &&  (transportLayerInst.state != STATE_MANUAL_INPUT))
+        {
+            // TODO: Move this into shellmatta_transport.c
+            /* use headerCounter to watch how many header fields have been worked on */
+            uint8_t headerCounter = 0u;
+            while ( (size > headerCounter) 
+                ||  (   (true == transportLayerInst.mandatory)
+                    &&  (size > headerCounter))
+                ||  (true == transportLayerInst.continueStep))
+            {
+                switch (transportLayerInst.state)
+                {
+                case STATE_GET_SOH:
+                    /* wait for SOH or go to payload */
+                    break;
+
+                case STATE_GET_PROTOCOL_VERSION:
+                    protocolVersion = data[headerCounter];
+                    break;
+
+                case STATE_GET_PACKET_TYPE:
+                    packetType = data[headerCounter];
+                    break;
+
+                case STATE_GET_PAYLOAD_LENGTH:
+                    payloadLength = (uint8_t)data[headerCounter];
+                    break;
+
+                case STATE_GET_SOURCE:
+                    source = data[headerCounter];
+                    break;
+
+                case STATE_GET_DESTINATION:
+                    destination = data[headerCounter];
+                    break;
+                
+                case STATE_GET_H2S_SEQUENCE_CNT:
+                    packetSequenceCounter_h2s = data[headerCounter];
+                    break;
+                
+                case STATE_GET_S2H_SEQUENCE_CNT:
+                    packetSequenceCounter_s2h = data[headerCounter];
+                    break;
+
+                case STATE_GET_PAYLOAD:
+                    if (0u == payloadLength)
+                    {
+                        transportLayerInst.continueStep = true;
+                    }
+                    payloadBuffer[payloadCounter++] = data[headerCounter];
+                    break;
+
+                case STATE_GET_CRC:
+                    transportLayerInst.continueStep = false;
+                    crc32 |= (uint8_t)data[headerCounter] << (SHELLMATTA_LENGTH_CRC - 1 - crcCounter++) * 8u;
+                    break;
+                
+                default:
+                    break;
+                }
+                /* handling of transport layer fsm */
+                ret = shellmatta_handle_transport_fsm(data);
+                
+                /* crc error handling */
+                if (SHELLMATTA_ERROR == ret)
+                {
+                    shellmatta_reset_transport();
+                    utils_writeEcho(handle, "crc error\r\n", 11);
+                    utils_terminateInput(inst);
+                    return SHELLMATTA_OK;
+                }
+
+                headerCounter++;
+
+                /* processes payload by forwarding it recursively without transport layer to processData() */
+                if (transportLayerInst.state == STATE_PROCESS_PAYLOAD)
+                {
+                    /* replace inst->write function pointer with transport layer write function */
+                    transportLayerInst.originalWrite = inst->write;
+                    inst->write = shellmatta_write_transport;
+                    
+                    /* recursive call with complete payload */
+                    shellmatta_processData(handle, payloadBuffer, payloadLength);
+                    
+                    /* set back inst->write function pointer to original */
+                    inst->write = transportLayerInst.originalWrite;
+                    shellmatta_handle_transport_fsm(data);
+                    return SHELLMATTA_OK;
+                }
+            }
+        }
+
+        if (    (transportLayerInst.active)
+            &&  (transportLayerInst.state != STATE_PROCESS_PAYLOAD)
+            &&  (transportLayerInst.state != STATE_MANUAL_INPUT))
+        {
+            return SHELLMATTA_OK;
+        }
+
         /** -# in busy mode - keep calling this command */
         if(NULL != inst->busyCmd)
         {
@@ -654,7 +759,7 @@ shellmatta_retCode_t shellmatta_processData(shellmatta_handle_t     handle,
                 }
             }
             /** -# ignore newline as first character (to be compatible to
-             * terminals sending newline after return */
+             * terminals sending newline after return) */
             else if((0u == inst->inputCount) && ('\n' == data[inst->byteCounter]))
             {
                 /* do nothing */
@@ -708,6 +813,13 @@ shellmatta_retCode_t shellmatta_processData(shellmatta_handle_t     handle,
     {
         ret = SHELLMATTA_USE_FAULT;
     }
+
+    /* if manual input happened, reset transport layer fsm back to initial state */
+    if (transportLayerInst.state == STATE_MANUAL_INPUT)
+    {
+        transportLayerInst.state = STATE_GET_SOH;
+    }
+
     return ret;
 }
 

src/shellmatta_crc.c

@@ -0,0 +1,134 @@
+/**
+ * @file    shellmatta_crc.c
+ * @brief   cyclic redundancy check functions of shellmatta
+ * @author  Simon Fischer <fischer.simon.1991@gmail.com>
+ */
+
+#include "shellmatta_crc.h"
+
+#ifndef CRC_NO_LOOKUP
+uint32_t crc32Table[] = {
+    /* 0x04c11db7 reflected */
+    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
+};
+#endif
+
+/**
+ * @brief       Reverses bits of a value.
+ * @param[in]   x       input value
+ * @param[in]   size    amount of bits used in value
+ */
+uint32_t reverse(uint32_t x, int bits)
+{
+    x = ((x & 0x55555555) << 1)  | ((x & 0xAAAAAAAA) >> 1);
+    x = ((x & 0x33333333) << 2)  | ((x & 0xCCCCCCCC) >> 2);
+    x = ((x & 0x0F0F0F0F) << 4)  | ((x & 0xF0F0F0F0) >> 4);
+    x = ((x & 0x00FF00FF) << 8)  | ((x & 0xFF00FF00) >> 8);
+    x = ((x & 0x0000FFFF) << 16) | ((x & 0xFFFF0000) >> 16);
+    return x >> (32 - bits);
+}
+
+/**
+ * @brief       Computes the crc32-checksum of a buffer.
+ * @param[in]   data            pointer to data buffer
+ * @param[in]   size            amount of bytes to be processed
+ */
+uint32_t crc32Calc(char* data, uint16_t size)
+{
+    #ifdef  CRC_NO_LOOKUP
+        return crc32Slow(data, size);
+    #else
+        return crc32Fast(data, size, crc32Table);
+    #endif
+}
+
+/**
+ * @brief       Computes the crc32-checksum of a buffer. O(4n)
+ * @param[in]   data            pointer to data buffer
+ * @param[in]   size            amount of bytes to be processed
+ */
+uint32_t crc32Slow(char* data, uint16_t size)
+{
+    uint16_t i;
+    uint8_t j;
+    uint8_t pivotByte;
+    uint32_t polynom = reverse(CRC32_POLYNOM, 32);
+
+    /* start with 0xffffffff */
+    uint32_t crcTemp = 0xffffffff;
+
+    for (i = 0; i < size; i++)
+    {
+        pivotByte = data[i];
+        for (j = 0; j < BITS_PER_BYTE; j++)
+        {
+            if ((crcTemp & 1) != (pivotByte & 1))
+            {
+                crcTemp = (crcTemp >> 1) ^ polynom;
+            }
+            else
+            {
+                crcTemp >>= 1;
+            }
+            pivotByte >>= 1;
+        }
+    }
+
+    /* final xor */
+    crcTemp ^= 0xffffffff;
+
+    return crcTemp;
+}
+
+#ifndef CRC_NO_LOOKUP
+/**
+ * @brief       Computes the crc32-checksum of a buffer. O(n)
+ * @param[in]   data            pointer to data buffer
+ * @param[in]   size            amount of bytes to be processed
+ * @param[in]   lookupTable     pointer to uint32_t lookup table for crc computation
+ */
+uint32_t crc32Fast(char* data, uint16_t size, uint32_t* lookupTable)
+{
+    uint16_t i;
+    uint32_t crcTemp = 0xffffffff;
+
+    for (i = 0; i < size; i++)
+    {
+        uint8_t index = data[i] ^ (crcTemp & 0xff);
+        crcTemp = lookupTable[index] ^ (crcTemp >> 8);
+    }
+
+    return ~crcTemp;
+}
+#endif

src/shellmatta_crc.h

@@ -0,0 +1,22 @@
+/**
+ * @file    shellmatta_crc.h
+ * @brief   cyclic redundancy check functions of shellmatta
+ * @author  Simon Fischer <fischer.simon.1991@gmail.com>
+ */
+
+#ifndef _SHELLMATTA_CRC_H_
+#define _SHELLMATTA_CRC_H_
+
+#include <stdint.h>
+
+#define CRC32_POLYNOM   0x04c11db7      /* crc-32 ethernet 802.3 */
+#define BITS_PER_BYTE   ((uint8_t)8)    /* amount of bits per byte; to avoid magic number */
+
+uint32_t crc32Calc(char* data, uint16_t size);
+uint32_t crc32Slow(char* data, uint16_t size);
+
+#ifndef CRC_NO_LOOKUP
+uint32_t crc32Fast(char* data, uint16_t size, uint32_t* lookupTable);
+#endif
+
+#endif /* _SHELLMATTA_CRC_H_ */

src/shellmatta_transport.c

@@ -0,0 +1,292 @@
+/**
+ * @file    shellmatta_transport.c
+ * @brief   transport layer functions of shellmatta
+ * @author  Simon Fischer <fischer.simon.1991@gmail.com>
+ */
+
+#include "shellmatta_transport.h"
+#include "shellmatta_crc.h"
+#include <string.h>
+#include <stdio.h>
+
+/* init global variables */
+uint8_t protocolVersion                     = 0u;
+shellmatta_transport_packet_t packetType    = 0u;
+uint32_t payloadLength                      = 0u;
+uint8_t source                              = 0u;
+uint8_t destination                         = 0u;
+uint32_t crc32                              = 0u;
+uint8_t payloadCounter                      = 0u;
+uint8_t crcCounter                          = 0u;
+uint8_t packetSequenceCounter_h2s           = 0u;
+uint8_t packetSequenceCounter_s2h           = 0u;
+shellmatta_transport_layer_t transportLayerInst = {
+    0,
+    0,
+    STATE_GET_SOH,
+    false,
+    false,
+    false,
+    NULL
+};
+char payloadBuffer[SHELLMATTA_PAYLOAD_MAXLENGTH + 1];
+
+/**
+ * @brief       Initializes the transportLayerInst
+ * @return      errorcode   #SHELLMATTA_OK
+ */
+shellmatta_retCode_t shellmatta_init_transport_inst()
+{
+    transportLayerInst.h2s_sequenceCnt = 0;
+    transportLayerInst.s2h_sequenceCnt = 0;
+    transportLayerInst.state = STATE_GET_SOH;
+    transportLayerInst.mandatory = false;
+    transportLayerInst.active = false;
+    transportLayerInst.continueStep = false;
+    memset(payloadBuffer, 0, SHELLMATTA_PAYLOAD_MAXLENGTH + 1);
+
+    return SHELLMATTA_OK;
+}
+
+/**
+ * @brief       Resets all values of tranportLayerInst except for sequence counters
+ * @return      errorcode   #SHELLMATTA_OK
+ */
+shellmatta_retCode_t shellmatta_reset_transport()
+{
+    transportLayerInst.state = STATE_GET_SOH;
+    protocolVersion = 0u;
+    packetType      = 0u;
+    payloadLength   = 0u;
+    source          = 0u;
+    destination     = 0u;
+    crc32           = 0u;
+    payloadCounter  = 0u;
+    crcCounter      = 0u;
+    transportLayerInst.active = false;
+    memset(payloadBuffer, 0, SHELLMATTA_PAYLOAD_MAXLENGTH + 1);
+
+    return SHELLMATTA_OK;
+}
+
+/**
+ * @brief       processes the passed amount of data
+ * @param[in]   data    pointer to input data to process
+ * @return      errorcode   #SHELLMATTA_OK
+ *                          #SHELLMATTA_ERROR   in case of crc error
+ */
+shellmatta_retCode_t shellmatta_handle_transport_fsm(char *data)
+{
+    switch (transportLayerInst.state)
+    {
+    case STATE_GET_SOH:
+        if (SHELLMATTA_START_OF_HEADER == *data)
+        {
+            transportLayerInst.state = STATE_GET_PROTOCOL_VERSION;
+            transportLayerInst.active = true;
+        }
+        else
+        {
+            transportLayerInst.state = STATE_MANUAL_INPUT;
+            transportLayerInst.active = false;
+        }
+        break;
+
+    case STATE_MANUAL_INPUT:
+        break;
+
+    case STATE_GET_PROTOCOL_VERSION:
+        transportLayerInst.state = STATE_GET_PACKET_TYPE;
+        break;
+
+    case STATE_GET_PACKET_TYPE:
+        transportLayerInst.state = STATE_GET_PAYLOAD_LENGTH;
+        break;
+
+    case STATE_GET_PAYLOAD_LENGTH:
+        transportLayerInst.state = STATE_GET_SOURCE;
+        break;
+
+    case STATE_GET_SOURCE:
+        transportLayerInst.state = STATE_GET_DESTINATION;
+        break;
+
+    case STATE_GET_DESTINATION:
+        transportLayerInst.state = STATE_GET_H2S_SEQUENCE_CNT;
+        break;
+
+    case STATE_GET_H2S_SEQUENCE_CNT:
+        transportLayerInst.state = STATE_GET_S2H_SEQUENCE_CNT;
+        break;
+
+    case STATE_GET_S2H_SEQUENCE_CNT:
+        if (packetType == PACKET_SEQ_CNT_REQUEST)
+        {
+            transportLayerInst.state = STATE_GET_CRC;
+        }
+        else
+        {
+            transportLayerInst.state = STATE_GET_PAYLOAD;
+        }
+        break;
+
+    case STATE_GET_PAYLOAD:
+        if (    (payloadLength <= payloadCounter)
+            &&  (true == transportLayerInst.active))
+        {
+            transportLayerInst.state = STATE_GET_CRC;
+        }
+        break;
+
+    case STATE_GET_CRC:
+        if (SHELLMATTA_LENGTH_CRC <= crcCounter)
+        {
+            /* for crc computation only */
+            char crcdata[SHELLMATTA_PAYLOAD_MAXLENGTH + 1 + SHELLMATTA_HEADER_LENGTH];
+            memset(crcdata, 0, SHELLMATTA_PAYLOAD_MAXLENGTH + 1 + SHELLMATTA_HEADER_LENGTH);
+            crcdata[0] = SHELLMATTA_START_OF_HEADER;
+            crcdata[1] = protocolVersion;
+            crcdata[2] = packetType;
+            crcdata[3] = payloadLength;
+            crcdata[4] = source;
+            crcdata[5] = destination;
+            crcdata[6] = packetSequenceCounter_h2s;
+            crcdata[7] = packetSequenceCounter_s2h;
+            strncat(&crcdata[8], payloadBuffer, payloadLength);
+
+            uint32_t refCrc;
+
+            refCrc = crc32Calc(crcdata, SHELLMATTA_HEADER_LENGTH + payloadLength);
+
+            if (crc32 == refCrc)
+            {
+                crcCounter = 0;
+                crc32 = 0;
+                transportLayerInst.state = STATE_GET_SOH;
+
+                /* crc is correct */
+                transportLayerInst.h2s_sequenceCnt++;
+
+                switch (packetType)
+                {
+                case PACKET_DATA:
+                    transportLayerInst.state = STATE_PROCESS_PAYLOAD;
+                    break;
+                
+                case PACKET_SEQ_CNT_REQUEST:
+                    /* change packet type to response */
+                    packetType = PACKET_SEQ_CNT_RESPOND;
+                    /* send out packet with no payload */
+                    shellmatta_write_transport("", 0);
+                    break;
+
+                case PACKET_SEQ_CNT_RESPOND:
+                    break;
+                
+                case PACKET_MAX_BUFFERSIZE_REQUEST:
+                    break;
+
+                case PACKET_MAX_BUFFERSIZE_RESPOND:
+                    break;
+                
+                case PACKET_SEARCH_DEVICE_REQUEST:
+                    break;
+                
+                case PACKET_SEARCH_DEVICE_RESPOND:
+                    break;
+
+                case PACKET_SET_ADDRESS_REQUEST:
+                    break;
+
+                case PACKET_SET_ADDRESS_RESPOND:
+                    break;
+
+                /* wrong packet type */
+                default:
+                    /* undo sequence counter increment */
+                    transportLayerInst.h2s_sequenceCnt--;
+                    break;
+                }
+                break;
+            }
+            else
+            {
+                // TODO: improve this
+                crcCounter = 0;
+                crc32 = 0;
+                transportLayerInst.state = STATE_GET_SOH;
+
+                /* crc is incorrect */
+                return SHELLMATTA_ERROR;
+            }
+        }
+        break;
+
+    case STATE_PROCESS_PAYLOAD:
+        transportLayerInst.state = STATE_GET_SOH;
+        protocolVersion = 0u;
+        packetType      = 0u;
+        payloadLength   = 0u;
+        source          = 0u;
+        destination     = 0u;
+        crc32           = 0u;
+        payloadCounter  = 0u;
+        crcCounter      = 0u;
+        transportLayerInst.active = false;
+        memset(payloadBuffer, 0, SHELLMATTA_PAYLOAD_MAXLENGTH + 1);
+        break;
+    
+    default:
+        break;
+    }
+
+    return SHELLMATTA_OK;
+}
+
+/**
+ * @brief       Wrapper function for the write-function of shellmatta handle
+ * 
+ * This function is used to transmit data with the tranport layer protocol.\n
+ * The input data is copied into a new array along with the header and crc32.\n
+ * The resulting buffer is the forwarded to the original write function.\n
+ * 
+ * @param[in]   data    pointer to input data to process
+ * @return      errorcode   #SHELLMATTA_OK
+ */
+shellmatta_retCode_t shellmatta_write_transport(const char* data, uint32_t length)
+{
+    /* create buffer for data + header + crc with maximum size */
+    uint8_t outputBuffer[   SHELLMATTA_HEADER_LENGTH +          /* length of header */
+                            SHELLMATTA_PAYLOAD_MAXLENGTH + 1 +  /* max length of payload */
+                            SHELLMATTA_LENGTH_CRC];             /* length of crc */
+    
+    uint32_t outPayloadLength = length + SHELLMATTA_HEADER_LENGTH + SHELLMATTA_LENGTH_CRC;
+
+    /* fill buffer with header data */
+    outputBuffer[0] = SHELLMATTA_START_OF_HEADER;           /* start of header */
+    outputBuffer[1] = PROTOCOL_VERSION;                     /* protocol version */
+    outputBuffer[2] = packetType;                           /* packet type */
+    outputBuffer[3] = length;                               /* payload length */
+    outputBuffer[4] = 0x00u;                                /* source */
+    outputBuffer[5] = 0x00u;                                /* destination */
+    outputBuffer[6] = transportLayerInst.h2s_sequenceCnt;   /* sequence counter host to shellmatta */
+    outputBuffer[7] = ++transportLayerInst.s2h_sequenceCnt; /* sequence counter shellmatta to host */
+
+    /* skip copying of payload in case of sequence counter response */
+    if (packetType != PACKET_SEQ_CNT_RESPOND)
+    {
+        memcpy(&outputBuffer[8], data, length);
+    }
+
+    uint32_t outCrc = crc32Calc((char*) outputBuffer, SHELLMATTA_HEADER_LENGTH + length);
+
+    /* append crc to end of payload */
+    outputBuffer[length + SHELLMATTA_HEADER_LENGTH + 0] = (uint8_t)(outCrc >> 0);
+    outputBuffer[length + SHELLMATTA_HEADER_LENGTH + 1] = (uint8_t)(outCrc >> 8);
+    outputBuffer[length + SHELLMATTA_HEADER_LENGTH + 2] = (uint8_t)(outCrc >> 16);
+    outputBuffer[length + SHELLMATTA_HEADER_LENGTH + 3] = (uint8_t)(outCrc >> 24);
+
+    /* use original write function to send full buffer */
+    shellmatta_retCode_t ret = transportLayerInst.originalWrite((char*) outputBuffer, outPayloadLength);
+    return ret;
+}

src/shellmatta_transport.h

@@ -0,0 +1,119 @@
+/**
+ * @file    shellmatta_transport.h
+ * @brief   transport layer functions of shellmatta
+ * @author  Simon Fischer <fischer.simon.1991@gmail.com>
+ */
+
+#ifndef _SHELLMATTA_TRANSPORT_H_
+#define _SHELLMATTA_TRANSPORT_H_
+
+#include "shellmatta.h"
+
+#define PROTOCOL_VERSION                    0x01u
+
+/** @brief value of start-of-header character */
+#define SHELLMATTA_START_OF_HEADER          0x01u
+
+/* payload length defines */
+/** @brief max length of a plain data payload */
+#define SHELLMATTA_PAYLOAD_MAXLENGTH        ((uint8_t)(255))
+/** @brief max length of a request sequence counters payload */
+#define SHELLMATTA_PAYLOAD_LEN_SEQ_REQ      ((uint8_t)(0))
+/** @brief max length of a respond sequence counters payload */
+#define SHELLMATTA_PAYLOAD_LEN_SEQ_RES      ((uint8_t)(0))
+/** @brief max length of a request buffersize payload */
+#define SHELLMATTA_PAYLOAD_LEN_BUFSIZE_REQ  ((uint8_t)(1))
+/** @brief max length of a respond buffersize payload */
+#define SHELLMATTA_PAYLOAD_LEN_BUFSIZE_RES  ((uint8_t)(1))
+
+/* header field length defines */
+#define SHELLMATTA_HEADER_LENGTH            ((uint8_t)(8))
+/** @brief length of headerfield: start of header */
+#define SHELLMATTA_LENGTH_SOH               ((uint8_t)(1))
+/** @brief length of headerfield: protocol version */
+#define SHELLMATTA_LENGTH_PROT_VERSION      ((uint8_t)(1))
+/** @brief length of headerfield: packet type */
+#define SHELLMATTA_LENGTH_PACKET_TYPE       ((uint8_t)(1))
+/** @brief length of headerfield: payload length */
+#define SHELLMATTA_LENGTH_PAYLOAD_LENGTH    ((uint8_t)(1))
+/** @brief length of headerfield: source */
+#define SHELLMATTA_LENGTH_SOURCE            ((uint8_t)(1))
+/** @brief length of headerfield: destination */
+#define SHELLMATTA_LENGTH_DESTINATION       ((uint8_t)(1))
+/** @brief length of headerfield: host to shell sequence counter */
+#define SHELLMATTA_LENGTH_H2S_SEQUENCE_CNT  ((uint8_t)(1))
+/** @brief length of headerfield: shell to host sequence counter */
+#define SHELLMATTA_LENGTH_S2H_SEQUENCE_CNT  ((uint8_t)(1))
+/** @brief length of headerfield: crc32 of header + payload without crc32 */
+#define SHELLMATTA_LENGTH_CRC               ((uint8_t)(4))
+/** @} */
+
+/**
+ * @brief definition of shellmatta transport layer states
+ */
+typedef enum
+{
+    STATE_GET_SOH                =0u,   /**< start of header state of transport layer */
+    STATE_MANUAL_INPUT              ,
+    STATE_GET_PROTOCOL_VERSION      ,   /**< protocol version state of transport layer */
+    STATE_GET_PACKET_TYPE           ,   /**< packet type state of transport layer */
+    STATE_GET_PAYLOAD_LENGTH        ,   /**< payload length state of transport layer */
+    STATE_GET_SOURCE                ,   /**< source state of transport layer */
+    STATE_GET_DESTINATION           ,   /**< destination state of transport layer */
+    STATE_GET_H2S_SEQUENCE_CNT      ,   /**< host to shellmatta sequence counter state of transport layer */
+    STATE_GET_S2H_SEQUENCE_CNT      ,   /**< shellmatta to host sequence counter state of transport layer */
+    STATE_GET_PAYLOAD               ,   /**< payload state of transport layer */
+    STATE_GET_CRC                   ,   /**< crc state of transport layer */
+    STATE_PROCESS_PAYLOAD
+} shellmatta_transport_state_t;
+
+/**
+ * @brief definition of shellmatta transport layer packet types
+ */
+typedef enum
+{
+    PACKET_DATA                     = 0x00u,    /**< packet type to send plain data */
+    PACKET_SEQ_CNT_REQUEST          = 0x01u,    /**< packet type to request sequence counters */
+    PACKET_SEQ_CNT_RESPOND          = 0x81u,    /**< packet type to respond with sequence counters */
+    PACKET_MAX_BUFFERSIZE_REQUEST   = 0x02u,    /**< packet type to set and request max buffersize */
+    PACKET_MAX_BUFFERSIZE_RESPOND   = 0x82u,    /**< packet type to respond with max buffersize */
+    PACKET_SEARCH_DEVICE_REQUEST    = 0x03u,    /**< UNUSED: packet type to request search for a device by unique id */
+    PACKET_SEARCH_DEVICE_RESPOND    = 0x83u,    /**< UNUSED: packet type to respond with search results */
+    PACKET_SET_ADDRESS_REQUEST      = 0x04u,    /**< UNUSED: packet type to set and request an address */
+    PACKET_SET_ADDRESS_RESPOND      = 0x84u     /**< UNUSED: packet type to respond with a set address */
+} shellmatta_transport_packet_t;
+
+typedef struct
+{
+    uint8_t h2s_sequenceCnt;                /**<  */
+    uint8_t s2h_sequenceCnt;                /**<  */
+    shellmatta_transport_state_t state;     /**<  */
+    bool mandatory;                         /**<  */
+    bool active;                            /**<  */
+    bool continueStep;                      /**<  */
+    shellmatta_write_t originalWrite;       /**<  */
+} shellmatta_transport_layer_t;
+
+extern uint8_t protocolVersion;
+extern shellmatta_transport_packet_t packetType;
+extern uint32_t payloadLength;
+extern uint8_t source;
+extern uint8_t destination;
+extern uint32_t crc32;
+extern uint8_t payloadCounter;
+extern uint8_t crcCounter;
+extern uint8_t packetSequenceCounter_h2s;
+extern uint8_t packetSequenceCounter_s2h;
+extern char payloadBuffer[SHELLMATTA_PAYLOAD_MAXLENGTH + 1];
+
+extern shellmatta_transport_layer_t transportLayerInst;
+
+shellmatta_retCode_t shellmatta_reset_transport();
+
+shellmatta_retCode_t shellmatta_init_transport_inst();
+
+shellmatta_retCode_t shellmatta_handle_transport_fsm(char *data);
+
+shellmatta_retCode_t shellmatta_write_transport(const char* data, uint32_t length);
+
+#endif /* _SHELLMATTA_TRANSPORT_H_ */