CRC5 creation method and example.

[ldong.1]

Hi. I'm working with L9369 H-bridge driver and i want to know how to calculate CRC code in C programming.

it's polynomial is X^5+X^2+1 and initial value is 0x1F(1 1111)

1. Do you have any documentation regarding CRC implementation in C code?

i got CRC documentable attched document, but i think it's 26 bit and responding CRC value is not matched.

2.i want to know X^5+X^2+1 polynomial's CRC Lookup Table and how to use lookup table in C code. i calculated it by manual, and have some result. i want to know i calculate it correctly.

0->0x0

1-> 0x5

2->0xa

3->0xf

4->0x14

5->0x11

.....

255-> 0x14 

3. i want to know how to use lookup table below 2 cases. and sample code.

when i try to calucate CRC value with lookup-table, it's result is different to the value calculated by manual.

(please let me know how to calculate in case of CRC initial(0x1F) value apply, not apply case)

0x1234 ( 0001 0010 0011 0100)

0x2D40CFF(0010 1101 0100 0000 1100 1111 1111)

4. I attached excel file that i calculate CRC value by manual.

atttched document says 26 bit stream is  "0 0000:0011 0 0000:0000:0000:0000" and CRC value is 0x0B. My CRC value is 0x15(with initial CRC), 0x1A(with out initial CRC)

i don't know why the result is different to me. please help to solve it.

thank you.

thank you.

[Tesla DeLorean]

Prior thread https://community.st.com/s/question/0D53W00001gxfOrSAI/reqeust-for-l9369-crc-calculation-documentation

TX: [0 0000:0011 0 0 0000:0000:0000:0000 01011]
0180000B (32) [0B]
CRC:0B -> 0180000B
 
TX: [0 0000:0010 0 1 0000:0000:0000:0000 11110]
0120001E (32) [1E]
CRC:1E -> 0120001E
 
TX: [0 0000:0100 0 0 0000:0000:0000:0000 01111]
0200000F (32) [0F]
CRC:0F -> 0200000F
 
0 10 0000:0011 0000:0101:0111:0000 0:1111
4060AE0F (32) [0F]
CRC:0F -> 4060AE0F
 
RX: [0 00 0000:0000 0000:0000:0000:0000 10001]
00000011 (32) [11]
CRC:11 -> 00000011
 
RX: [0 10 0000:0011 0000:0101:0111:0000 01111]
4060AE0F (32) [0F]
CRC:0F -> 4060AE0F
 
RX: [0 00 0000:0010 0000:1001:0011:0011 01111] Table 6c, seems inconsistent
0041266F (32) [0F]
CRC:0A -> 0041266A
 
RX: [0 00 0000:0011 0000:0101:0111:0000 00110]
0060AE06 (32) [06]
CRC:06 -> 0060AE06
 
RX: [1000:1000:1111:1111:1111:1111:1111:0010]
88FFFFF2 (32) [12]
CRC:12 -> 88FFFFF2
 
RX: [0 00 1111:1101 0000:0001:0001:1111 00000]
1FA023E0 (32) [00]
CRC:00 -> 1FA023E0
 
RX: [0 00 0000:0011 0000:0101:0111:0000 00110]
0060AE06 (32) [06]
CRC:06 -> 0060AE06

[Tesla DeLorean]

Table 9 test values seem good

Table 9
TX: [0 1001:0000 0 0 0000:0000:0000:0000 01111]
4800000F (32) [0F]
CRC:0F -> 4800000F
 
RX: [0 00 0000:0000 0000:0000:0000:0000 10001]
00000011 (32) [11]
CRC:11 -> 00000011
 
TX: [0 0000:0011 0 1 0000:0000:0000:0000 01011]
01A0000B (32) [0B]
CRC:0B -> 01A0000B
 
RX: [1000:0000:1111:1111:1111:1111:1110:0101]
80FFFFE5 (32) [05]
CRC:05 -> 80FFFFE5
 
TX: [0 0000:0011 0 0 0000:0000:0000:0000 01011]
0180000B (32) [0B]
CRC:0B -> 0180000B
 
RX: [0 00 0000:0011 0000:0101:0111:0010 01100]
0060AE4C (32) [0C]
CRC:0C -> 0060AE4C
 
TX: [0 0000:0011 0 0 0000:0000:0000:0000 01011]
0180000B (32) [0B]
CRC:0B -> 0180000B
 
RX: [0 10 0000:0011 0000:0101:0111:0010 00101]
4060AE45 (32) [05]
CRC:05 -> 4060AE45
 
TX: [0 1111:1101 0 1 0000:0000:0000:0000 00000]
7EA00000 (32) [00]
CRC:00 -> 7EA00000
 
RX: [0 00 0000:0011 0000:0101:0111:0000 00110]
0060AE06 (32) [06]
CRC:06 -> 0060AE06
 
TX: [0 0000:0011 0 0 0000:0000:0000:0000 01011]
0180000B (32) [0B]
CRC:0B -> 0180000B
 
RX: [0 00 1111:1101 0000:0000:0001:1111 11100]
1FA003FC (32) [1C]
CRC:1C -> 1FA003FC

[ldong.1]

hello. thank for reply. i'm modifying your example code for calculate data input with polynomial '100101', it's hard to implement. please help me to make getting CRC code function.

and i calculated your example, it seem that CRC code is wrong.

please check belows.

1. i calculated first Tx message's CRC, but i can't get CRC 0x01011 with initial value 0x1F. i think this example don't care CRC initial value.

TX: [0 0000:0011 0 0 0000:0000:0000:0000 01011]

-> payload is 0x60000, CRC is 0x0B(without initial value)

2.i calculated sencond Tx Message

TX: [0 0000:0010 0 1 0000:0000:0000:0000 11110]

->payload is 0x40000, CRC is 0x0F(without initial value)

[Tesla DeLorean]

void rule21a(uint32_t data)
{
  int i;
  uint32_t test = (data & 0xFFC00000) | ((data & 0x1FFFE0) << 1); // Remove bit 20, high-order align
  uint32_t crc;
 
  crc = 0x1F << 27; // Initial, aligned high-order to match data
  crc = crc ^ test; // Apply data
  for(i=0; i<26; i++) // Consume data (shortened)
    if (crc & 0x80000000)
      crc = (crc << 1) ^ (0x05 << 27); // Bitwise application
    else
      crc <<= 1;
 
  crc = (crc >> 27) & 0x1F; // Recover, align, mask computed value
 
  printf("CRC:%02X -> %08X %s\n\n", crc, (data & 0xFFFFFFE0) ^ crc, ((data & 0x1F) != crc) ? "???" : "");
} // sourcer32@gmail.com

[Tesla DeLorean]

My 8-bit table ended up like this

  static const uint8_t crctbl[] = { // CRC-5 8-bit table, sourcer32@gmail.com
    0x00,0x28,0x50,0x78,0xA0,0x88,0xF0,0xD8,0x68,0x40,0x38,0x10,0xC8,0xE0,0x98,0xB0,
    0xD0,0xF8,0x80,0xA8,0x70,0x58,0x20,0x08,0xB8,0x90,0xE8,0xC0,0x18,0x30,0x48,0x60,
    0x88,0xA0,0xD8,0xF0,0x28,0x00,0x78,0x50,0xE0,0xC8,0xB0,0x98,0x40,0x68,0x10,0x38,
    0x58,0x70,0x08,0x20,0xF8,0xD0,0xA8,0x80,0x30,0x18,0x60,0x48,0x90,0xB8,0xC0,0xE8,
    0x38,0x10,0x68,0x40,0x98,0xB0,0xC8,0xE0,0x50,0x78,0x00,0x28,0xF0,0xD8,0xA0,0x88,
    0xE8,0xC0,0xB8,0x90,0x48,0x60,0x18,0x30,0x80,0xA8,0xD0,0xF8,0x20,0x08,0x70,0x58,
    0xB0,0x98,0xE0,0xC8,0x10,0x38,0x40,0x68,0xD8,0xF0,0x88,0xA0,0x78,0x50,0x28,0x00,
    0x60,0x48,0x30,0x18,0xC0,0xE8,0x90,0xB8,0x08,0x20,0x58,0x70,0xA8,0x80,0xF8,0xD0,
    0x70,0x58,0x20,0x08,0xD0,0xF8,0x80,0xA8,0x18,0x30,0x48,0x60,0xB8,0x90,0xE8,0xC0,
    0xA0,0x88,0xF0,0xD8,0x00,0x28,0x50,0x78,0xC8,0xE0,0x98,0xB0,0x68,0x40,0x38,0x10,
    0xF8,0xD0,0xA8,0x80,0x58,0x70,0x08,0x20,0x90,0xB8,0xC0,0xE8,0x30,0x18,0x60,0x48,
    0x28,0x00,0x78,0x50,0x88,0xA0,0xD8,0xF0,0x40,0x68,0x10,0x38,0xE0,0xC8,0xB0,0x98,
    0x48,0x60,0x18,0x30,0xE8,0xC0,0xB8,0x90,0x20,0x08,0x70,0x58,0x80,0xA8,0xD0,0xF8,
    0x98,0xB0,0xC8,0xE0,0x38,0x10,0x68,0x40,0xF0,0xD8,0xA0,0x88,0x50,0x78,0x00,0x28,
    0xC0,0xE8,0x90,0xB8,0x60,0x48,0x30,0x18,0xA8,0x80,0xF8,0xD0,0x08,0x20,0x58,0x70,
    0x10,0x38,0x40,0x68,0xB0,0x98,0xE0,0xC8,0x78,0x50,0x28,0x00,0xD8,0xF0,0x88,0xA0 };

[Tesla DeLorean]

I can make the Programmable HW CRC peripheral process it too, but the value/utility is questionable.

[ldong.1]

Hello. thank you very much for replying to my refit repetitive question.

i know above source code how to get CRC. but i have one question.

if data is not 32bit data, for example, 0x40000000, in this case, below initial value shifting seems wrong.

" crc = 0x1F << 27; // Initial, aligned high-order to match data"

i think above code works propely only when in case MSB(31bit) exist.

correct?

[ldong.1]

Hello. thank you very much for replying to my refit repetitive question.

i have 2 question.

1. Do you use polynomial X^5+X^2+1? it seems wrong, for second data of CRCtable, crctbl[1] = 0x28.

but the value i calculate is 0x05. how to you get 0x28?

1. i want to know how to use look up table. i already know how to use CRC-8 lookup table, but when i try it with CRC-5 table, it's result was wrong. do you know how to use CRC-5 lookuptable? and have any sourcecode?

thank you.

[Tesla DeLorean]

I am left aligning in the register for computational efficiency, allowing me to process 1, 2, 4 or 8-bits via tables

For the 26-bit value the least significant 6-bits (right) are zero, [5..0]=0, so the data exists in [31..6]