Контрольная сумма crc16 modbus

communication.py

 import serial
 import time
+from crc import Calculator, Crc16
 
 def open_serial(port, baudrate):
     try: #пытаемся открыть serial порт
@@ -20,14 +21,23 @@ def open_serial(port, baudrate):
     return serial_port
 
 
-
-def serial_exchange(serial_port, transmit_bytes, required_response_length, timeout = 1):
+#если всё ок, возвращает полученный массив байт
+#если required_response_length == 0, возвращает пустой массив
+#если таймаут или не сходится crc, возвращает None
+def serial_exchange(serial_port, transmit_array, required_response_length, timeout = 1):
     if serial_port is None:
         raise OSError
 
+    transmit_bytes = bytearray(transmit_array)
+
+    crc_calculator = Calculator(Crc16.MODBUS)
+    crc16 = crc_calculator.checksum(transmit_bytes)
+    crc16_bytes = crc16.to_bytes(length=2, byteorder='big')
+    transmit_bytes += crc16_bytes
+
     serial_port.reset_input_buffer()
     serial_port.reset_output_buffer()
-    serial_port.write(bytearray(transmit_bytes))
+    serial_port.write(transmit_bytes)
 
     if required_response_length == 0:
         return bytes([])
@@ -42,4 +52,11 @@ def serial_exchange(serial_port, transmit_bytes, required_response_length, timeo
         return None
 
     response = serial_port.read(required_response_length)
+
+    #минимум 1 байт данных + 2 байта crc
+    if len(response) >= 3:
+        response_crc16 = int.from_bytes([response[-2], response[-1]], byteorder='big', signed=False)
+        if not crc_calculator.verify(response[:-2], response_crc16):
+            return None
+
     return response

hddtempserial.py

@@ -75,18 +75,18 @@ def initialize(serial_port):
         config['controlGroups'][1]['copyFromGroupIndex'],
         config['controlGroups'][2]['copyFromGroupIndex']
     ]
-    response_length = 1
+    response_length = 3
 
     response = serial_exchange(serial_port, transmit_bytes, response_length, config['arduinoTimeoutSec'])
 
     if response is None:
-        print('Initialize failed')
+        print('Initialize no valid response')
     else:
         if response[0] == arduino_response_codes.initialize_ok:
             initialized = True
             print('Initialize ok')
         else:
-            print('Initialize not ok')
+            print('Initialize bad response')
 
 
 def poll(serial_port):
@@ -102,12 +102,12 @@ def poll(serial_port):
         (temperatures[2] >> 8) & 0xff,
         temperatures[2] & 0xff,
     ]
-    response_length = 16
+    response_length = 18
 
     response = serial_exchange(serial_port, transmit_bytes, response_length, config['arduinoTimeoutSec'])
     if response is None:
         initialized = False
-        print('Poll failed')
+        print('Poll no valid response')
     else:
         if response[0] == arduino_response_codes.poll_noinit:
             initialized = False
@@ -128,7 +128,7 @@ def poll(serial_port):
             return True
         else:
             initialized = False
-            print('Poll not ok')
+            print('Poll bad response')
 
     return False
 
@@ -164,11 +164,8 @@ if __name__ == "__main__":
     if baudrate is None:
         print('Baudrate is not specified (neither in config nor in command line)')
         exit()
-    serial_port = open_serial(port, baudrate)
-    if serial_port is None:
-        print('Failed to open serial port')
-        exit()
 
+    serial_port = open_serial(port, baudrate)
 
 
     try:

hddtempserial/hddtempserial.ino

-//#include <Wire.h>
-
 #define FAN_COUNT 6 //Количество вентиляторов
 #define CONTROL_COUNT 3 //Количество групп управления
 #define BAUDRATE 19200 //Скорость serial порта
@@ -161,6 +159,71 @@ bool initialized = false;
 
 
 
+
+
+const unsigned short crc16table[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
+};
+
+uint16_t crc16_calc(uint8_t *data, uint16_t len)
+{
+  uint16_t crc = 0xFFFF;
+  uint8_t nTemp;
+
+  while (len--)
+  {
+    nTemp = *data++ ^ crc;
+    crc >>= 8;
+    crc ^= crc16table[nTemp];
+  }
+
+  return crc;
+}
+
+
+uint8_t add_crc(uint8_t *buf, uint8_t len) {
+  uint16_t crc16 = crc16_calc(buf, len);
+  buf[len] = crc16 >> 8;
+  buf[len+1] = crc16 & 0xff;
+
+  len += 2;
+  return len;
+}
+
+
+
+
 uint16_t get_avg_rpm(fan* fan_ptr) {
   uint32_t avg_rpm = 0;
   
@@ -174,7 +237,6 @@ uint16_t get_avg_rpm(fan* fan_ptr) {
 
 
 void process_command() {
-  uint8_t cmd_code = 0;
   uint8_t cmd_buffer[32] = {};
   uint8_t cmd_length = 0;
   
@@ -183,16 +245,18 @@ void process_command() {
   uint8_t response_length = 1;
 
   //читаем первый байт (код команды)
-  if (Serial.readBytes(&cmd_code, 1) == 0)
+  if (Serial.readBytes(cmd_buffer, 1) == 0)
     return;
 
-  //по коду команды понимаем сколько еще байтов надо принять
+  uint8_t cmd_code = cmd_buffer[0];
+
+  //по коду команды понимаем длину команды (с учетом байта кода команды и двух байт crc)
   switch(cmd_code) {
     case pc_command_codes::initialize:
-      cmd_length = 7;
+      cmd_length = 10;
       break;
     case pc_command_codes::poll:
-      cmd_length = 6;
+      cmd_length = 9;
       break;
     default:
       break;
@@ -200,63 +264,70 @@ void process_command() {
 
   //читаем команду
   if (cmd_length > 0) {
-    uint8_t bytes_read = Serial.readBytes(cmd_buffer, cmd_length);
-
-    //выполняем команду
-    if (bytes_read == cmd_length) {
-      switch(cmd_code) {
-        case pc_command_codes::initialize:          
-          pc_poll_interval_sec = cmd_buffer[0];
-        
-          control_a.target_temperature = cmd_buffer[1];
-          control_b.target_temperature = cmd_buffer[2];
-          control_c.target_temperature = cmd_buffer[3];
-          
-          control_a.copy_from = cmd_buffer[4];
-          control_b.copy_from = cmd_buffer[5];
-          control_c.copy_from = cmd_buffer[6];
-
-          initialized = true;
-          
-          response_buffer[0] = arduino_response_codes::initialize_ok;
-          response_length = 1;
-          break;
-          
-        case pc_command_codes::poll:
-          control_a.temperature = cmd_buffer[0] << 8 | cmd_buffer[1];
-          control_b.temperature = cmd_buffer[2] << 8 | cmd_buffer[3];
-          control_c.temperature = cmd_buffer[4] << 8 | cmd_buffer[5];
-
-          if (initialized)
-            response_buffer[0] = arduino_response_codes::poll_ok;
-          else
-            response_buffer[0] = arduino_response_codes::poll_noinit;
-
-          for (int i = 0; i < FAN_COUNT; i++){
-            uint16_t rpm = get_avg_rpm(&fans[i]);
-            response_buffer[i*2+1] = rpm >> 8;
-            response_buffer[i*2+2] = rpm & 0xff;
-          }
-          response_buffer[13] = OCR1A;
-          response_buffer[14] = OCR2A;
-          response_buffer[15] = OCR2B;
-          response_length = 16;
-          break;
-          
-        default:
-          break;
+    //принимаем оставшиемся байты
+    uint8_t bytes_read = Serial.readBytes(&cmd_buffer[1], cmd_length-1);
+
+    if (bytes_read == cmd_length-1) {
+      uint16_t cmd_crc16 = cmd_buffer[cmd_length-2] << 8 | cmd_buffer[cmd_length-1];
+      uint16_t check_crc16 = crc16_calc(cmd_buffer, cmd_length-2);
+
+      if (cmd_crc16 == check_crc16) {
+        //выполняем команду
+        switch(cmd_code) {
+          case pc_command_codes::initialize:
+            pc_poll_interval_sec = cmd_buffer[1];
+
+            control_a.target_temperature = cmd_buffer[2];
+            control_b.target_temperature = cmd_buffer[3];
+            control_c.target_temperature = cmd_buffer[4];
+            control_a.copy_from = cmd_buffer[5];
+            control_b.copy_from = cmd_buffer[6];
+            control_c.copy_from = cmd_buffer[7];
+
+            initialized = true;
+
+            response_buffer[0] = arduino_response_codes::initialize_ok;
+
+            response_length = 1;
+            break;
+
+          case pc_command_codes::poll:
+            control_a.temperature = cmd_buffer[1] << 8 | cmd_buffer[2];
+            control_b.temperature = cmd_buffer[3] << 8 | cmd_buffer[4];
+            control_c.temperature = cmd_buffer[5] << 8 | cmd_buffer[6];
+
+            if (initialized)
+              response_buffer[0] = arduino_response_codes::poll_ok;
+            else
+              response_buffer[0] = arduino_response_codes::poll_noinit;
+            for (int i = 0; i < FAN_COUNT; i++){
+              uint16_t rpm = get_avg_rpm(&fans[i]);
+              response_buffer[i*2+1] = rpm >> 8;
+              response_buffer[i*2+2] = rpm & 0xff;
+            }
+            response_buffer[13] = OCR1A;
+            response_buffer[14] = OCR2A;
+            response_buffer[15] = OCR2B;
+
+            response_length = 16;
+            response_length = add_crc(response_buffer, response_length);
+            break;
+
+          default:
+            break;
+        }
+
+        last_poll_time = millis();
+        pc_respond = true;
       }
     }
-    
-    last_poll_time = millis();
-    pc_respond = true;
   }
 
   while (Serial.available()) // очистка буфера
     Serial.read();
 
-  //ответ
-  Serial.write(response_buffer, response_length);
+  response_length = add_crc(response_buffer, response_length);
+  Serial.write(response_buffer, response_length); //посылаем ответ
 }