Arduino sending data with checksum CRC16

bally94 · October 9, 2021, 11:18am

Now, as I have deleted all unnessesary serial outputs I get all the sent data on the master and on the slave side! What is the problem sometimes, that the master does not get all the data, but after pressing the reset button it works perfectly. Perhaps a problem after uploading the code or because the slave Arduino is not an original Arduino!?

Master sender code:

/*Arduino 1 has the SC16IS750 connected on SDA/SCL
 *TX/RX of the SC16IS750 is connected to Arduino 2
 *VCC/GND
 *I2C of the SC16IS750 is connected to VCC
 *A0 and A1 of the SC16IS750 is connected as shown in the address table below
 */
 
#include <Wire.h>
#include <SC16IS750.h>

SC16IS750 i2cuart = SC16IS750(SC16IS750_PROTOCOL_I2C,SC16IS750_ADDRESS_AA);   /*Address table:  A1    A0    Address
                                                                                               VDD   VDD    0x90 => AA
                                                                                               VDD   GND    0x92 => AB
                                                                                               VDD   SCL    0x94 => AC
                                                                                               VDD   SDA    0x96 => AD
                                                                                               GND   VDD    0x98 => BA
                                                                                               GND   GND    0x9A => BB
                                                                                               GND   SCL    0x9C => BC
                                                                                               GND   SDA    0x9E => BD
                                                                                               SCL   VDD    0xA0 => CA
                                                                                               SCL   GND    0xA2 => CB
                                                                                               SCL   SCL    0xA4 => CC
                                                                                               SCL   SDA    0xA6 => CD
                                                                                               SDA   VDD    0xA8 => DA
                                                                                               SDA   GND    0xAA => DB
                                                                                               SDA   SCL    0xAC => DC
                                                                                               SDA   SDA    0xAE => DD
                                                                                               */

const byte bufferSize {10};
char serialBuffer[bufferSize+1] {""};
char incomingData[bufferSize] {""};
char value[bufferSize] {""};
char variable[bufferSize] {""};
uint16_t crc = 0;    //checksum crc
byte crcData[2] {""};        //create array for packet serial
byte crcDataRec[2] {""};        //create array for packet serial

int E = 0;
int F = 0;
int G = 0;
int H = 0;
int BUT = 0;


void setup()
{
  i2cuart.begin(38400);
  Serial.begin(38400);
}

void loop()
{
  readCommand();
  
  
  Serial.print("E = ");
  Serial.println(E);
  Serial.print("F = ");
  Serial.println(F);
  Serial.print("G = ");
  Serial.println(G);
  Serial.print("H = ");
  Serial.println(H);
  Serial.print("BUT = ");
  Serial.println(BUT);

  
  command("A01");
  command("B57");
  command("C183");
  command("D122");
  command("@19");
 
}



void command(String value) {
  memset(serialBuffer, 0, sizeof serialBuffer);
  sendToI2CUART(serialBuffer, value);
}


void sendToI2CUART (char *const buffer, String command)
{
  command.toCharArray(buffer, bufferSize);
  const size_t characters {strlen(buffer)};
  Serial.print("laenge: "); Serial.println(characters);

  for(byte index = 0; index < characters; index++){            //create the checksum for the array data[i] with 0 <= i <= 3
        crc16(buffer[index]);                                  //call the function crc16
      }
      crc = getCRC();
      byte crcIndex = characters;
      byte crcIndex2 = crcIndex++;
      buffer[crcIndex] = crc >> 8;                         //store checksum in data array
      buffer[crcIndex2] = crc;
      crc = 0;
      
  for (byte i = 0; i < characters; i++)
  {
    i2cuart.write(buffer[i]);
    Serial.print("gesendet: ");
    Serial.println(buffer[i]);
  }
  i2cuart.write('\0');
  i2cuart.write(buffer[crcIndex]);
  //Serial.print("gesendet CRC: ");
  //Serial.println(buffer[crcIndex],HEX);
  i2cuart.write(buffer[crcIndex2]);
  //Serial.print("gesendet CRC: ");
  //Serial.println(buffer[crcIndex2],HEX);
  i2cuart.write('\n');

}


//Calculates CRC16 of nBytes of data[index] in byte array
void crc16(uint8_t data) {

  int i;
  crc = crc ^ ((uint16_t)data << 8);
  for (i=0; i<8; i++){
    if (crc & 0x8000){
      crc = (crc << 1) ^ 0x1021;
    }
    else{
      crc <<= 1;
    }
  }
}

uint16_t getCRC() {
  return crc;
}


void readCommand(){

  char var;
  int val = 0;
  byte i = 0;
  byte j = 0;
  byte k = 0;
  byte state = 0;

  while(i2cuart.available()) {
    char m = i2cuart.read();
    if(m == '\0') {
      state = 1;
      i = 0;
    }

    if(m == '\n') {
      state = 2;
      i = 0;
    }

    switch(state){
      case 0: incomingData[i++] = m;
              //Serial.print("incomingData = ");
              //Serial.println(incomingData[i]);
              break;
      case 1: if(m != '\0'){
                crcData[i++] = m;
                //Serial.print("empfangen CRC: ");
                //Serial.println(crcData[i]);
              }
              else {
                break;
              }
              break;
      case 2: for(byte index = 0; index < strlen(incomingData); index++){            //create the checksum for the array data[i] with 0 <= i <= 3
                crc16(incomingData[index]);                                  //call the function crc16
              }
              crc = getCRC();
              crcDataRec[0] = crc >> 8;                         //store checksum in data array
              crcDataRec[1] = crc;
              crc = 0;

              //Serial.print("crcData[0] = ");
              //Serial.println(crcData[0],HEX);
              //Serial.print("crcDataRec[0] = ");
              //Serial.println(crcDataRec[0],HEX);
              //Serial.print("crcData[1] = ");
              //Serial.println(crcData[1],HEX);
              //Serial.print("crcDataRec[1] = ");
              //Serial.println(crcDataRec[1],HEX);

              if(crcData[0] == crcDataRec[0] && crcData[1] == crcDataRec[1]) {
                while(i <= strlen(incomingData) ) {
                  if(isdigit(incomingData[i]) == true) {
                    value[j] = incomingData[i];
                    j++;
                    i++;
                  }
                  else {
                    variable[k] = incomingData[i];
                    k++;
                    i++;
                  }
                }
                memset(incomingData, 0, sizeof incomingData);
                j = 0;
                k = 0;
                i = 0;
      
                val = atoi(value);  //making the integer part
                var = variable[0];

                memset(value, 0, sizeof value);
                memset(variable, 0, sizeof variable);

                switch(var) {
                  case 'E' : E = val;
                             break;
                  case 'F' : F = val;
                             break;
                  case 'G' : G = val;
                             break;
                  case 'H' : H = val;
                             break;
                  case '#' : BUT = val;
                             break;
                }
              }
              else if(crcData[0] != crcDataRec[0] || crcData[1] != crcDataRec[1]){
                memset(incomingData, 0, sizeof incomingData);
              }
              state = 0;
              memset(crcData, 0, sizeof crcData);
              memset(crcDataRec, 0, sizeof crcDataRec);
              break;
    }
  }
}

Slave receiver code:

/*Arduino 2 has the SC16IS750 connected on TX/RX
 */

const byte bufferSize {10};
char serialBuffer[bufferSize+1] {""};
char incomingData[bufferSize] {""};
char value[bufferSize] {""};
char variable[bufferSize] {""};
uint16_t crc = 0;    //checksum crc
byte crcData[2] {""};
byte crcDataRec[2] {""};

int A = 0;
int B = 0;
int C = 0;
int D = 0;
int BUT = 0;

  
void setup()
{
  Serial.begin(38400);
  
}

void loop() {

  readCommand();

  
  Serial.print("A = ");
  Serial.println(A);
  Serial.print("B = ");
  Serial.println(B);
  Serial.print("C = ");
  Serial.println(C);
  Serial.print("D = ");
  Serial.println(D);
  Serial.print("BUT = ");
  Serial.println(BUT);


  command("E10");
  command("F5");
  command("G147");
  command("H251");
  command("#33");
  
}


void command(String value) {
  memset(serialBuffer, 0, sizeof serialBuffer);
  sendToUART(serialBuffer, value);
}


void sendToUART (char *const buffer, String command)
{
  command.toCharArray(buffer, bufferSize);
  const size_t characters {strlen(buffer)};
  //Serial.print("laenge: "); Serial.println(characters);

  for(byte index = 0; index < characters; index++){            //create the checksum for the array data[i] with 0 <= i <= 3
        crc16(buffer[index]);                                  //call the function crc16
      }
      crc = getCRC();
      byte crcIndex = characters;
      byte crcIndex2 = crcIndex++;
      buffer[crcIndex] = crc >> 8;                         //store checksum in data array
      buffer[crcIndex2] = crc;
      crc = 0;

  for (byte i = 0; i < characters; i++)
  {
    Serial.write(buffer[i]);
    //Serial.print("gesendet: ");
    //Serial.println(buffer[i]);
  }
  Serial.write('\0');
  Serial.write(buffer[crcIndex]);
  //Serial.print("gesendet CRC: ");
  //Serial.println(buffer[crcIndex],HEX);
  Serial.write(buffer[crcIndex2]);
  //Serial.print("gesendet CRC: ");
  //Serial.println(buffer[crcIndex2],HEX);
  Serial.write('\n');

}


//Calculates CRC16 of nBytes of data[index] in byte array
void crc16(uint8_t data) {

  int i;
  crc = crc ^ ((uint16_t)data << 8);
  for (i=0; i<8; i++){
    if (crc & 0x8000){
      crc = (crc << 1) ^ 0x1021;
    }
    else{
      crc <<= 1;
    }
  }
}

uint16_t getCRC() {
  return crc;
}


void readCommand(){

  char var;
  int val = 0;
  byte i = 0;
  byte j = 0;
  byte k = 0;
  byte state = 0;
  
  while(Serial.available()) {
    char m = Serial.read();
    if(m == '\0') {
      state = 1;
      i = 0;
    }

    if(m == '\n') {
      state = 2;
      i = 0;
    }

    switch(state){
      case 0: incomingData[i++] = m;
              //Serial.print("incomingData = ");
              //Serial.println(incomingData[i]);
              break;
      case 1: if(m != '\0'){
                crcData[i++] = m;
                //Serial.print("empfangen CRC: ");
                //Serial.println(crcData[i]);
              }
              else {
                break;
              }
              break;
      case 2: for(byte index = 0; index < strlen(incomingData); index++){            //create the checksum for the array data[i] with 0 <= i <= 3
                crc16(incomingData[index]);                                  //call the function crc16
              }
              crc = getCRC();
              crcDataRec[0] = crc >> 8;                         //store checksum in data array
              crcDataRec[1] = crc;
              crc = 0;

              //Serial.print("crcData[0] = ");
              //Serial.println(crcData[0],HEX);
              //Serial.print("crcDataRec[0] = ");
              //Serial.println(crcDataRec[0],HEX);
              //Serial.print("crcData[1] = ");
              //Serial.println(crcData[1],HEX);
              //Serial.print("crcDataRec[1] = ");
              //Serial.println(crcDataRec[1],HEX);
  
              if(crcData[0] == crcDataRec[0] && crcData[1] == crcDataRec[1]) {
                while(i <= strlen(incomingData) ) {
                  if(isdigit(incomingData[i]) == true) {
                    value[j] = incomingData[i];
                    j++;
                    i++;
                  }
                  else {
                    variable[k] = incomingData[i];
                    k++;
                    i++;
                  }
                }
                memset(incomingData, 0, sizeof incomingData);
                j = 0;
                k = 0;
                i = 0;
      
                val = atoi(value);  //making the integer part
                var = variable[0];

                memset(value, 0, sizeof value);
                memset(variable, 0, sizeof variable);

                switch(var) {
                case 'A' : A = val;
                           break;
                case 'B' : B = val;
                           break;
                case 'C' : C = val;
                           break;
                case 'D' : D = val;
                           break;
                case '@' : BUT = val;
                           break;
                }
              }
              else if(crcData[0] != crcDataRec[0] || crcData[1] != crcDataRec[1]){
                memset(incomingData, 0, sizeof incomingData);
              }
              state = 0;
              memset(crcData, 0, sizeof crcData);
              memset(crcDataRec, 0, sizeof crcDataRec);
              break;
    }
  }
}

Master serial monitor output:

laenge: 3
gesendet: A
gesendet: 0
gesendet: 1
laenge: 3
gesendet: B
gesendet: 5
gesendet: 7
laenge: 4
gesendet: C
gesendet: 1
gesendet: 8
gesendet: 3
laenge: 4
gesendet: D
gesendet: 1
gesendet: 2
gesendet: 2
laenge: 3
gesendet: @
gesendet: 1
gesendet: 9
E = 10
F = 5
G = 147
H = 251
BUT = 33
laenge: 3
gesendet: A
gesendet: 0
gesendet: 1
laenge: 3
gesendet: B
gesendet: 5
gesendet: 7
laenge: 4
gesendet: C
gesendet: 1
gesendet: 8
gesendet: 3
laenge: 4
gesendet: D
gesendet: 1
gesendet: 2
gesendet: 2
laenge: 3
gesendet: @
gesendet: 1
gesendet: 9
E = 10
F = 5
G = 147
H = 251
BUT = 33
laenge: 3
gesendet: A
gesendet: 0
gesendet: 1
laenge: 3
gesendet: B
gesendet: 5
gesendet: 7
laenge: 4
gesendet: C
gesendet: 1
gesendet: 8
gesendet: 3
laenge: 4
gesendet: D
gesendet: 1
gesendet: 2
gesendet: 2
laenge: 3
gesendet: @
gesendet: 1
gesendet: 9
E = 10
F = 5
G = 147
H = 251
BUT = 33
laenge: 3
gesendet: A
gesendet: 0
gesendet: 1
laenge: 3
gesendet: B
gesendet: 5
gesendet: 7
laenge: 4
gesendet: C
gesendet: 1
gesendet: 8
gesendet: 3
laenge: 4
gesendet: D
gesendet: 1
gesendet: 2
gesendet: 2
laenge: 3
gesendet: @
gesendet: 1
gesendet: 9
E = 10
F = 5
G = 147
H = 251
BUT = 33
laenge: 3
gesendet: A
gesendet: 0
gesendet: 1
laenge: 3
gesendet: B
gesendet: 5
gesendet: 7
laenge: 4
gesendet: C
gesendet: 1
gesendet: 8
gesendet: 3
laenge: 4
gesendet: D
gesendet: 1
gesendet: 2
gesendet: 2
laenge: 3
gesendet: @
gesendet: 1
gesendet: 9
E = 10
F = 5
G = 147
H = 251
BUT = 33

Slave serial montiro output:

E10 □□
F5 □□
G147 B□
H251 □□
#33 □`
A = 1
B = 57
C = 183
D = 122
BUT = 19
E10 □□
F5 □□
G147 B□
H251 □□
#33 □`
A = 1
B = 57
C = 183
D = 122
BUT = 19
E10 □□
F5 □□
G147 B□
H251 □□
#33 □`
A = 1
B = 57
C = 183
D = 122
BUT = 19
E10 □□
F5 □□
G147 B□
H251 □□
#33 □`
A = 1
B = 57
C = 183
D = 122
BUT = 19

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Arduino sending data with checksum CRC16

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