TMAG5170: TMAG5170 CRC Algorithm

David Walker

Part Number: TMAG5170

There have been a lot of questions about the CRC on this part. Most of the recommendations are to send a command to disable the CRC or alternatively use a slow, bit-by-bit algorithm. The below code implements the CRC for this part using a byte-by-byte algorithm. It is based on a state machine approach where the present state is the current CRC and the input data is eight bits of data.

static const uint8_t crc_lut[16][128] = {
  {48, 86, 252, 154, 139, 237, 71, 33, 101, 3, 169, 207, 222, 184, 18, 116, 154, 252, 86, 48, 33, 71, 237, 139, 207, 169, 3, 101, 116, 18, 184, 222, 71, 33, 139, 237, 252, 154, 48, 86, 18, 116, 222, 184, 169, 207, 101, 3, 237, 139, 33, 71, 86, 48, 154, 252, 184, 222, 116, 18, 3, 101, 207, 169, 222, 184, 18, 116, 101, 3, 169, 207, 139, 237, 71, 33, 48, 86, 252, 154, 116, 18, 184, 222, 207, 169, 3, 101, 33, 71, 237, 139, 154, 252, 86, 48, 169, 207, 101, 3, 18, 116, 222, 184, 252, 154, 48, 86, 71, 33, 139, 237, 3, 101, 207, 169, 184, 222, 116, 18, 86, 48, 154, 252, 237, 139, 33, 71},
  {101, 3, 169, 207, 222, 184, 18, 116, 48, 86, 252, 154, 139, 237, 71, 33, 207, 169, 3, 101, 116, 18, 184, 222, 154, 252, 86, 48, 33, 71, 237, 139, 18, 116, 222, 184, 169, 207, 101, 3, 71, 33, 139, 237, 252, 154, 48, 86, 184, 222, 116, 18, 3, 101, 207, 169, 237, 139, 33, 71, 86, 48, 154, 252, 139, 237, 71, 33, 48, 86, 252, 154, 222, 184, 18, 116, 101, 3, 169, 207, 33, 71, 237, 139, 154, 252, 86, 48, 116, 18, 184, 222, 207, 169, 3, 101, 252, 154, 48, 86, 71, 33, 139, 237, 169, 207, 101, 3, 18, 116, 222, 184, 86, 48, 154, 252, 237, 139, 33, 71, 3, 101, 207, 169, 184, 222, 116, 18},
  {154, 252, 86, 48, 33, 71, 237, 139, 207, 169, 3, 101, 116, 18, 184, 222, 48, 86, 252, 154, 139, 237, 71, 33, 101, 3, 169, 207, 222, 184, 18, 116, 237, 139, 33, 71, 86, 48, 154, 252, 184, 222, 116, 18, 3, 101, 207, 169, 71, 33, 139, 237, 252, 154, 48, 86, 18, 116, 222, 184, 169, 207, 101, 3, 116, 18, 184, 222, 207, 169, 3, 101, 33, 71, 237, 139, 154, 252, 86, 48, 222, 184, 18, 116, 101, 3, 169, 207, 139, 237, 71, 33, 48, 86, 252, 154, 3, 101, 207, 169, 184, 222, 116, 18, 86, 48, 154, 252, 237, 139, 33, 71, 169, 207, 101, 3, 18, 116, 222, 184, 252, 154, 48, 86, 71, 33, 139, 237},
  {207, 169, 3, 101, 116, 18, 184, 222, 154, 252, 86, 48, 33, 71, 237, 139, 101, 3, 169, 207, 222, 184, 18, 116, 48, 86, 252, 154, 139, 237, 71, 33, 184, 222, 116, 18, 3, 101, 207, 169, 237, 139, 33, 71, 86, 48, 154, 252, 18, 116, 222, 184, 169, 207, 101, 3, 71, 33, 139, 237, 252, 154, 48, 86, 33, 71, 237, 139, 154, 252, 86, 48, 116, 18, 184, 222, 207, 169, 3, 101, 139, 237, 71, 33, 48, 86, 252, 154, 222, 184, 18, 116, 101, 3, 169, 207, 86, 48, 154, 252, 237, 139, 33, 71, 3, 101, 207, 169, 184, 222, 116, 18, 252, 154, 48, 86, 71, 33, 139, 237, 169, 207, 101, 3, 18, 116, 222, 184},
  {71, 33, 139, 237, 252, 154, 48, 86, 18, 116, 222, 184, 169, 207, 101, 3, 237, 139, 33, 71, 86, 48, 154, 252, 184, 222, 116, 18, 3, 101, 207, 169, 48, 86, 252, 154, 139, 237, 71, 33, 101, 3, 169, 207, 222, 184, 18, 116, 154, 252, 86, 48, 33, 71, 237, 139, 207, 169, 3, 101, 116, 18, 184, 222, 169, 207, 101, 3, 18, 116, 222, 184, 252, 154, 48, 86, 71, 33, 139, 237, 3, 101, 207, 169, 184, 222, 116, 18, 86, 48, 154, 252, 237, 139, 33, 71, 222, 184, 18, 116, 101, 3, 169, 207, 139, 237, 71, 33, 48, 86, 252, 154, 116, 18, 184, 222, 207, 169, 3, 101, 33, 71, 237, 139, 154, 252, 86, 48},
  {18, 116, 222, 184, 169, 207, 101, 3, 71, 33, 139, 237, 252, 154, 48, 86, 184, 222, 116, 18, 3, 101, 207, 169, 237, 139, 33, 71, 86, 48, 154, 252, 101, 3, 169, 207, 222, 184, 18, 116, 48, 86, 252, 154, 139, 237, 71, 33, 207, 169, 3, 101, 116, 18, 184, 222, 154, 252, 86, 48, 33, 71, 237, 139, 252, 154, 48, 86, 71, 33, 139, 237, 169, 207, 101, 3, 18, 116, 222, 184, 86, 48, 154, 252, 237, 139, 33, 71, 3, 101, 207, 169, 184, 222, 116, 18, 139, 237, 71, 33, 48, 86, 252, 154, 222, 184, 18, 116, 101, 3, 169, 207, 33, 71, 237, 139, 154, 252, 86, 48, 116, 18, 184, 222, 207, 169, 3, 101},
  {237, 139, 33, 71, 86, 48, 154, 252, 184, 222, 116, 18, 3, 101, 207, 169, 71, 33, 139, 237, 252, 154, 48, 86, 18, 116, 222, 184, 169, 207, 101, 3, 154, 252, 86, 48, 33, 71, 237, 139, 207, 169, 3, 101, 116, 18, 184, 222, 48, 86, 252, 154, 139, 237, 71, 33, 101, 3, 169, 207, 222, 184, 18, 116, 3, 101, 207, 169, 184, 222, 116, 18, 86, 48, 154, 252, 237, 139, 33, 71, 169, 207, 101, 3, 18, 116, 222, 184, 252, 154, 48, 86, 71, 33, 139, 237, 116, 18, 184, 222, 207, 169, 3, 101, 33, 71, 237, 139, 154, 252, 86, 48, 222, 184, 18, 116, 101, 3, 169, 207, 139, 237, 71, 33, 48, 86, 252, 154},
  {184, 222, 116, 18, 3, 101, 207, 169, 237, 139, 33, 71, 86, 48, 154, 252, 18, 116, 222, 184, 169, 207, 101, 3, 71, 33, 139, 237, 252, 154, 48, 86, 207, 169, 3, 101, 116, 18, 184, 222, 154, 252, 86, 48, 33, 71, 237, 139, 101, 3, 169, 207, 222, 184, 18, 116, 48, 86, 252, 154, 139, 237, 71, 33, 86, 48, 154, 252, 237, 139, 33, 71, 3, 101, 207, 169, 184, 222, 116, 18, 252, 154, 48, 86, 71, 33, 139, 237, 169, 207, 101, 3, 18, 116, 222, 184, 33, 71, 237, 139, 154, 252, 86, 48, 116, 18, 184, 222, 207, 169, 3, 101, 139, 237, 71, 33, 48, 86, 252, 154, 222, 184, 18, 116, 101, 3, 169, 207},
  {222, 184, 18, 116, 101, 3, 169, 207, 139, 237, 71, 33, 48, 86, 252, 154, 116, 18, 184, 222, 207, 169, 3, 101, 33, 71, 237, 139, 154, 252, 86, 48, 169, 207, 101, 3, 18, 116, 222, 184, 252, 154, 48, 86, 71, 33, 139, 237, 3, 101, 207, 169, 184, 222, 116, 18, 86, 48, 154, 252, 237, 139, 33, 71, 48, 86, 252, 154, 139, 237, 71, 33, 101, 3, 169, 207, 222, 184, 18, 116, 154, 252, 86, 48, 33, 71, 237, 139, 207, 169, 3, 101, 116, 18, 184, 222, 71, 33, 139, 237, 252, 154, 48, 86, 18, 116, 222, 184, 169, 207, 101, 3, 237, 139, 33, 71, 86, 48, 154, 252, 184, 222, 116, 18, 3, 101, 207, 169},
  {139, 237, 71, 33, 48, 86, 252, 154, 222, 184, 18, 116, 101, 3, 169, 207, 33, 71, 237, 139, 154, 252, 86, 48, 116, 18, 184, 222, 207, 169, 3, 101, 252, 154, 48, 86, 71, 33, 139, 237, 169, 207, 101, 3, 18, 116, 222, 184, 86, 48, 154, 252, 237, 139, 33, 71, 3, 101, 207, 169, 184, 222, 116, 18, 101, 3, 169, 207, 222, 184, 18, 116, 48, 86, 252, 154, 139, 237, 71, 33, 207, 169, 3, 101, 116, 18, 184, 222, 154, 252, 86, 48, 33, 71, 237, 139, 18, 116, 222, 184, 169, 207, 101, 3, 71, 33, 139, 237, 252, 154, 48, 86, 184, 222, 116, 18, 3, 101, 207, 169, 237, 139, 33, 71, 86, 48, 154, 252},
  {116, 18, 184, 222, 207, 169, 3, 101, 33, 71, 237, 139, 154, 252, 86, 48, 222, 184, 18, 116, 101, 3, 169, 207, 139, 237, 71, 33, 48, 86, 252, 154, 3, 101, 207, 169, 184, 222, 116, 18, 86, 48, 154, 252, 237, 139, 33, 71, 169, 207, 101, 3, 18, 116, 222, 184, 252, 154, 48, 86, 71, 33, 139, 237, 154, 252, 86, 48, 33, 71, 237, 139, 207, 169, 3, 101, 116, 18, 184, 222, 48, 86, 252, 154, 139, 237, 71, 33, 101, 3, 169, 207, 222, 184, 18, 116, 237, 139, 33, 71, 86, 48, 154, 252, 184, 222, 116, 18, 3, 101, 207, 169, 71, 33, 139, 237, 252, 154, 48, 86, 18, 116, 222, 184, 169, 207, 101, 3},
  {33, 71, 237, 139, 154, 252, 86, 48, 116, 18, 184, 222, 207, 169, 3, 101, 139, 237, 71, 33, 48, 86, 252, 154, 222, 184, 18, 116, 101, 3, 169, 207, 86, 48, 154, 252, 237, 139, 33, 71, 3, 101, 207, 169, 184, 222, 116, 18, 252, 154, 48, 86, 71, 33, 139, 237, 169, 207, 101, 3, 18, 116, 222, 184, 207, 169, 3, 101, 116, 18, 184, 222, 154, 252, 86, 48, 33, 71, 237, 139, 101, 3, 169, 207, 222, 184, 18, 116, 48, 86, 252, 154, 139, 237, 71, 33, 184, 222, 116, 18, 3, 101, 207, 169, 237, 139, 33, 71, 86, 48, 154, 252, 18, 116, 222, 184, 169, 207, 101, 3, 71, 33, 139, 237, 252, 154, 48, 86},
  {169, 207, 101, 3, 18, 116, 222, 184, 252, 154, 48, 86, 71, 33, 139, 237, 3, 101, 207, 169, 184, 222, 116, 18, 86, 48, 154, 252, 237, 139, 33, 71, 222, 184, 18, 116, 101, 3, 169, 207, 139, 237, 71, 33, 48, 86, 252, 154, 116, 18, 184, 222, 207, 169, 3, 101, 33, 71, 237, 139, 154, 252, 86, 48, 71, 33, 139, 237, 252, 154, 48, 86, 18, 116, 222, 184, 169, 207, 101, 3, 237, 139, 33, 71, 86, 48, 154, 252, 184, 222, 116, 18, 3, 101, 207, 169, 48, 86, 252, 154, 139, 237, 71, 33, 101, 3, 169, 207, 222, 184, 18, 116, 154, 252, 86, 48, 33, 71, 237, 139, 207, 169, 3, 101, 116, 18, 184, 222},
  {252, 154, 48, 86, 71, 33, 139, 237, 169, 207, 101, 3, 18, 116, 222, 184, 86, 48, 154, 252, 237, 139, 33, 71, 3, 101, 207, 169, 184, 222, 116, 18, 139, 237, 71, 33, 48, 86, 252, 154, 222, 184, 18, 116, 101, 3, 169, 207, 33, 71, 237, 139, 154, 252, 86, 48, 116, 18, 184, 222, 207, 169, 3, 101, 18, 116, 222, 184, 169, 207, 101, 3, 71, 33, 139, 237, 252, 154, 48, 86, 184, 222, 116, 18, 3, 101, 207, 169, 237, 139, 33, 71, 86, 48, 154, 252, 101, 3, 169, 207, 222, 184, 18, 116, 48, 86, 252, 154, 139, 237, 71, 33, 207, 169, 3, 101, 116, 18, 184, 222, 154, 252, 86, 48, 33, 71, 237, 139},
  {3, 101, 207, 169, 184, 222, 116, 18, 86, 48, 154, 252, 237, 139, 33, 71, 169, 207, 101, 3, 18, 116, 222, 184, 252, 154, 48, 86, 71, 33, 139, 237, 116, 18, 184, 222, 207, 169, 3, 101, 33, 71, 237, 139, 154, 252, 86, 48, 222, 184, 18, 116, 101, 3, 169, 207, 139, 237, 71, 33, 48, 86, 252, 154, 237, 139, 33, 71, 86, 48, 154, 252, 184, 222, 116, 18, 3, 101, 207, 169, 71, 33, 139, 237, 252, 154, 48, 86, 18, 116, 222, 184, 169, 207, 101, 3, 154, 252, 86, 48, 33, 71, 237, 139, 207, 169, 3, 101, 116, 18, 184, 222, 48, 86, 252, 154, 139, 237, 71, 33, 101, 3, 169, 207, 222, 184, 18, 116},
  {86, 48, 154, 252, 237, 139, 33, 71, 3, 101, 207, 169, 184, 222, 116, 18, 252, 154, 48, 86, 71, 33, 139, 237, 169, 207, 101, 3, 18, 116, 222, 184, 33, 71, 237, 139, 154, 252, 86, 48, 116, 18, 184, 222, 207, 169, 3, 101, 139, 237, 71, 33, 48, 86, 252, 154, 222, 184, 18, 116, 101, 3, 169, 207, 184, 222, 116, 18, 3, 101, 207, 169, 237, 139, 33, 71, 86, 48, 154, 252, 18, 116, 222, 184, 169, 207, 101, 3, 71, 33, 139, 237, 252, 154, 48, 86, 207, 169, 3, 101, 116, 18, 184, 222, 154, 252, 86, 48, 33, 71, 237, 139, 101, 3, 169, 207, 222, 184, 18, 116, 48, 86, 252, 154, 139, 237, 71, 33},
};

static inline uint8_t get_next_crc(uint8_t crc, uint8_t data) {
  uint8_t crc_hl = crc_lut[crc][data / 2];
  return (data & 1) ? (crc_hl >> 4) : (crc_hl & 0xF);
}

static uint8_t calc_crc(uint32_t data) {
  uint8_t crc;

  crc = get_next_crc(0xF, (data >> 24) & 0xFF);  // first CRC value is 0xF (the initial value)
  crc = get_next_crc(crc, (data >> 16) & 0xFF);
  crc = get_next_crc(crc, (data >>  8) & 0xFF);
  crc = get_next_crc(crc, (data >>  0) & 0xF0);  // note the 0xF0 for the zero padding
  return crc;
}

If anyone can think of a way to reduce the table size further, let me know.

over 2 years ago

0 Scott Bryson over 2 years ago

TI__Genius 15250 points

David,

Please note the reference code on this reply:

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/980300/tmag5170-q1-crc-calculation-target-range

Thanks,

Scott

0 David Walker over 2 years ago in reply to Scott Bryson

Prodigy 40 points

Certainly, that algorithm is correct, but I'm working in C, not Verilog.

+1 Scott Bryson over 2 years ago in reply to David Walker

TI__Genius 15250 points

David,

The snippet at the bottom of that thread that condenses the calculation was taken from this code written in C:

dataTx[0] = (address) | 0x80; // Address + read bit (Start with 1)
dataTx[3] = 0x10; // CMD = 0b01

uint32_t n;
n= (dataTx[0] << 24)|(dataTx[1] << 16)|(dataTx[2] << 8)|(dataTx[3]);
int j = 0;
while (n>0)
{
d[j] = n%2;
n = n/2;
j++;
}

crc[0] = d[30] ^ d[26] ^ d[25] ^ d[24] ^ d[23] ^ d[21] ^ d[19] ^ d[18] ^ d[15] ^ d[11] ^ d[10] ^ d[9] ^ d[8] ^ d[6] ^ d[4] ^ d[3] ^ d[0] ^ 1;
crc[1] = d[31] ^ d[30] ^ d[27] ^ d[23] ^ d[22] ^ d[21] ^ d[20] ^ d[18] ^ d[16] ^ d[15] ^ d[12] ^ d[8] ^ d[7] ^ d[6] ^ d[5] ^ d[3] ^ d[1] ^ d[0] ^ 1 ^ 1;
crc[2] = d[31] ^ d[28] ^ d[24] ^ d[23] ^ d[22] ^ d[21] ^ d[19] ^ d[17] ^ d[16] ^ d[13] ^ d[9] ^ d[8] ^ d[7] ^ d[6] ^ d[4] ^ d[2] ^ d[1] ^ 1 ^ 1;
crc[3] = d[29] ^ d[25] ^ d[24] ^ d[23] ^ d[22] ^ d[20] ^ d[18] ^ d[17] ^ d[14] ^ d[10] ^ d[9] ^ d[8] ^ d[7] ^ d[5] ^ d[3] ^ d[2] ^ 1;

dataTx[3] = dataTx[3] | (crc[3] << 3) | (crc[2] << 2) | (crc[1] << 1) | (crc[0]);

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TMAG5170: TMAG5170 CRC Algorithm