Duplicate x^8 + x^5 + x^4 + x^0 CRC with ST IP?

[hbarta2]

Posted on January 12, 2017 at 21:10

This CRC is used by an I2C peripheral and documented at 

http://www.sensirion.co.jp/fileadmin/user_upload/customers/sensirion/Dokumente/GasFlow/Sensirion_Gas_Flow_SFM3000_CRC_Checksum.pdf

  

Can this CRC be duplicated using the CRC IP on the STM32F7? The HAL library defaults to X^4 + X^2 + X^1 and I seem unable to change that (and it states that the exponents must be less than 8.) I tried substituting the code for the polynomial above (0x131) and the HAL initialization code rejected it.

Is this a shortcoming of the library or a limit of the H/W?

Code to init the CRC produced by Cube is:

/* CRC init function */

static void MX_CRC_Init(void)

{

hcrc.Instance = CRC;

hcrc.Init.DefaultPolynomialUse = DEFAULT_POLYNOMIAL_DISABLE;

hcrc.Init.DefaultInitValueUse = DEFAULT_INIT_VALUE_DISABLE;

hcrc.Init.GeneratingPolynomial = 0x7;

hcrc.Init.CRCLength = CRC_POLYLENGTH_8B;

hcrc.Init.InitValue = 65535;

hcrc.Init.InputDataInversionMode = CRC_INPUTDATA_INVERSION_NONE;

hcrc.Init.OutputDataInversionMode = CRC_OUTPUTDATA_INVERSION_DISABLE;

hcrc.InputDataFormat = CRC_INPUTDATA_FORMAT_BYTES;

if (HAL_CRC_Init(&hcrc) != HAL_OK)

{

      Error_Handler();

}

}

(Hmmm not sure I've got this code formatting thing right.)

(Hmmm.2 - two CRC posts in one day!)

#crc

[Tesla DeLorean]

Posted on January 12, 2017 at 21:15

Would be 0x31, the high order bit is inferred. Initial value is zero.

[hbarta2]

Posted on January 12, 2017 at 21:29

Yes, that works - Thanks!

Cube accepts X5+X4+X0 as the polynomial and it generates the desired result.

I should add that the other thing I needed to change was the initial value to 0xFF in the model code. I don't know if it was done differently with a different devide (I'm working with a different Sensiron sensor) or if it was an oversight in the example code, but that was necessary to get the correct results for the data read from the Sensiron humidity/temperature sensor. (Or perhaps it was misapplication of the code.) I made a similar change in the CRC IP configuration.

thanks,

hank

[Tesla DeLorean]

Posted on January 12, 2017 at 21:43

//****************************************************************************
// CRC x8 + x5 + x4 + 1 Sensirion
// http://www.sensirion.co.jp/fileadmin/user_upload/customers/sensirion/Dokumente/GasFlow/Sensirion_Gas_Flow_SFM3000_CRC_Checksum.pdf
// Implementation Copyright (C) 2017 [e-mail] All Rights Reserved
//****************************************************************************
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
typedef unsigned char uint8_t;
#define POLY 0x31 // Polynomial x8 + x5 + x4 + 1, left shifting
//****************************************************************************
uint8_t Slow_CRC_Cal8Bits(uint8_t crc, size_t Size, uint8_t *Buffer)
{
 int i;
 while(Size--)
 {
 crc = crc ^ *Buffer++;
 for(i=0; i<8; i++)
 {
 if (crc & 0x80)
 crc = (crc << 1) ^ POLY;
 else
 crc = (crc << 1);
 }
 }
 return(crc);
}
//****************************************************************************
uint8_t Quick_CRC_Cal8Bits(uint8_t crc, size_t Size, uint8_t *Buffer)
{
 static const uint8_t CrcTable[] = { // Sensirion 8-bit CRC x8+x5+x4+1
 0x00,0x31,0x62,0x53,0xC4,0xF5,0xA6,0x97, // 0x31 nibble table - [e-mail]
 0xB9,0x88,0xDB,0xEA,0x7D,0x4C,0x1F,0x2E };
 while(Size--)
 {
 crc = crc ^ *Buffer++; // Apply data byte
 crc = (crc << 4) ^ CrcTable[(crc >> 4) & 0xF]; // Apply CRC 4-bit at a time, 2 rounds
 crc = (crc << 4) ^ CrcTable[(crc >> 4) & 0xF];
 }
 return(crc);
}
//****************************************************************************
uint8_t Fast_CRC_Cal8Bits(uint8_t crc, size_t Size, uint8_t *Buffer)
{
 static const uint8_t CrcTable[] = { // Sensirion 8-bit CRC x8+x5+x4+1
 0x00,0x31,0x62,0x53,0xC4,0xF5,0xA6,0x97, // 0x31 byte table - [e-mail]
 0xB9,0x88,0xDB,0xEA,0x7D,0x4C,0x1F,0x2E,
 0x43,0x72,0x21,0x10,0x87,0xB6,0xE5,0xD4,
 0xFA,0xCB,0x98,0xA9,0x3E,0x0F,0x5C,0x6D,
 0x86,0xB7,0xE4,0xD5,0x42,0x73,0x20,0x11,
 0x3F,0x0E,0x5D,0x6C,0xFB,0xCA,0x99,0xA8,
 0xC5,0xF4,0xA7,0x96,0x01,0x30,0x63,0x52,
 0x7C,0x4D,0x1E,0x2F,0xB8,0x89,0xDA,0xEB,
 0x3D,0x0C,0x5F,0x6E,0xF9,0xC8,0x9B,0xAA,
 0x84,0xB5,0xE6,0xD7,0x40,0x71,0x22,0x13,
 0x7E,0x4F,0x1C,0x2D,0xBA,0x8B,0xD8,0xE9,
 0xC7,0xF6,0xA5,0x94,0x03,0x32,0x61,0x50,
 0xBB,0x8A,0xD9,0xE8,0x7F,0x4E,0x1D,0x2C,
 0x02,0x33,0x60,0x51,0xC6,0xF7,0xA4,0x95,
 0xF8,0xC9,0x9A,0xAB,0x3C,0x0D,0x5E,0x6F,
 0x41,0x70,0x23,0x12,0x85,0xB4,0xE7,0xD6,
 0x7A,0x4B,0x18,0x29,0xBE,0x8F,0xDC,0xED,
 0xC3,0xF2,0xA1,0x90,0x07,0x36,0x65,0x54,
 0x39,0x08,0x5B,0x6A,0xFD,0xCC,0x9F,0xAE,
 0x80,0xB1,0xE2,0xD3,0x44,0x75,0x26,0x17,
 0xFC,0xCD,0x9E,0xAF,0x38,0x09,0x5A,0x6B,
 0x45,0x74,0x27,0x16,0x81,0xB0,0xE3,0xD2,
 0xBF,0x8E,0xDD,0xEC,0x7B,0x4A,0x19,0x28,
 0x06,0x37,0x64,0x55,0xC2,0xF3,0xA0,0x91,
 0x47,0x76,0x25,0x14,0x83,0xB2,0xE1,0xD0,
 0xFE,0xCF,0x9C,0xAD,0x3A,0x0B,0x58,0x69,
 0x04,0x35,0x66,0x57,0xC0,0xF1,0xA2,0x93,
 0xBD,0x8C,0xDF,0xEE,0x79,0x48,0x1B,0x2A,
 0xC1,0xF0,0xA3,0x92,0x05,0x34,0x67,0x56,
 0x78,0x49,0x1A,0x2B,0xBC,0x8D,0xDE,0xEF,
 0x82,0xB3,0xE0,0xD1,0x46,0x77,0x24,0x15,
 0x3B,0x0A,0x59,0x68,0xFF,0xCE,0x9D,0xAC };
 while(Size--)
 {
 crc = crc ^ *Buffer++; // Apply data byte
 crc = CrcTable[crc & 0xFF]; // Apply CRC 8-bits at a time
 }
 return(crc);
}
//****************************************************************************
int main(int argc, char **argv)
{
 uint8_t crc;
 uint8_t test[2] = { 0x87,0x01 }; // 0xBC
 printf('crc=%02X Slow
', Slow_CRC_Cal8Bits(0x00, sizeof(test), test));
 printf('crc=%02X Quick
', Quick_CRC_Cal8Bits(0x00, sizeof(test), test));
 printf('crc=%02X Fast
', Fast_CRC_Cal8Bits(0x00, sizeof(test), test));
 return(1);
}
//****************************************************************************
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