hi, i am fresher to this stm32 , i am doing project on modbus but i am not able to calculate crc value and i am not getting what i need to add to my code to calculate crc in modbus . can anyone help me its urgent. Thank you

[Tesla DeLorean]

I posted some examples in the past, the search is pretty hopeless here

This is an old one, gives a couple of working examples of MODBUS CRC computation

https://community.st.com/s/contentdocument/0690X0000060JWXQA2

https://community.st.com/s/question/0D50X00009XkgXtSAJ/programmable-crc-peripheral-in-newer-stm32-devices

https://community.st.com/s/question/0D50X00009XkbNMSAZ/crc-computation

// sourcer32@gmail.com
// 16-Bit CRC of Right Shifting MODBUS Polynomial 0xA001
 
#include <windows.h>
#include <stdio.h>
 
typedef unsigned char uint8_t;
typedef unsigned short uint16_t;
 
uint16_t Crc16Modbus(uint16_t Crc, uint8_t Data)
{
  int i;
  Crc = Crc ^ Data;
  for(i=0; i<8; i++)
    if (Crc & 0x0001)
      Crc = (Crc >> 1) ^ 0xA001; // Polynomial used by MODBUS
    else
      Crc = (Crc >> 1); // Right shifting algorithm
  return(Crc);
}
 
int main(int argc, char **argv)
{
  uint8_t TestData[] = { 0x01,0x04,0x75,0x54,0x00,0x02 };
  uint16_t crc;
  int i;
  crc = 0xFFFF; // Initial state
  for(i=0; i<sizeof(TestData); i++)
    crc = Crc16Modbus(crc, TestData[i]);
  printf("CRC = %04X\n", crc);
  return(1);
}

http://www.catb.org/~esr/faqs/smart-questions.html#urgent

[waclawek.jan]

Which STM32?

What did you do?

JW

[Tesla DeLorean]

Based on recent postings stm32f103, so needs to be done in software.

Faster methods described in one of attached posts.

[Lchal.1]

Thank you