topic Re: LPC824 CRC CALC in LPC Microcontrollers

LPC824 CRC CALC

pauloferreira — Tue, 18 Jul 2017 14:55:23 GMT

Using LPC824 CRC engine :

Polynomial = x16 + x12 + x5 + 1 (ccitt)
Seed Value = 0xFFFF
Bit order reverse for data input: Yes
1's complement for data input: NO
Bit order reverse for CRC sum: Yes
1's complement for CRC sum: NO
CRC_MODE = 0x0000 0014
CRC_SEED = 0x0000 FFFF

For string "ABC" result crc 0x10f0

Using another devices to calc with same parameters result 0x60d0 (ex. CRC calculation )

Any ideas please ?

Re: LPC824 CRC CALC

kerryzhou — Thu, 20 Jul 2017 07:43:53 GMT

Hello PAULO FERREIRA,

I think your problem is caused by your LPC824 CRC configuration.

Because I also test your desired CRC for "ABC" =0x41,0x42,0x43, I can get the correct CRC data 0x60d.

Now, post my test code for your reference.

1. Your desired information

Polynomial = x16 + x12 + x5 + 1 (ccitt)
Seed Value = 0xFFFF
Bit order reverse for data input: Yes
1's complement for data input: NO
Bit order reverse for CRC sum: Yes
1's complement for CRC sum: NO

According to the register description

So, MODE should be:0x14 .

2. function

static const uint8_t kerrytest[] = {0x41,0x42,0x43};

uint32_t kerry_result;

In main, call:

int main(void)
{

   /* Board Initialization */
   SystemCoreClockUpdate();
   Board_Init();

/* Chip Initialization */
Chip_CRC_Init();

/* Enable SysTick Timer */
SysTick_Config(SystemCoreClock / TICKRATE_HZ);

   /* Loop tests with occasional forced error */
   while (1) {
      kerry_test(kerrytest,3);

}
}

void kerry_test(const uint8_t *data, uint32_t bytes)
{

   LPC_CRC->MODE = 0x14;
   LPC_CRC->SEED = CRC_SEED_CCITT;

   while (bytes > 0) {
       Chip_CRC_Write8(*data);
       data++;
       bytes--;
   }
   kerry_result = Chip_CRC_Sum();//Chip_CRC_CRC8(kerrytest, 3);
}

After test, the debug result is:

You can find the kerry_result is 0x60d0 .

3. Use CRC calculation tool

CRC calculation

In conclusion, you can find the result in CRC calculation tool and the LPC824 code is the same.

Wish it helps you!

If you still have question, please kindly let me know!

Have a great day,
Kerry

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Re: LPC824 CRC CALC

pauloferreira — Thu, 20 Jul 2017 13:23:31 GMT

Thanks Kerry.

My mistake was definition of CRC_WR_DATA pointer like uint32_t .

I was writing 32 bits at a time, and the correct was 8 bits to each sum.

Nice help. Regards.

Re: LPC824 CRC CALC

kerryzhou — Fri, 21 Jul 2017 01:46:22 GMT

Hello PAULO FERREIRA,

That's very good to hear your problem is solved.

If your problem is solved, please help me to mark the correct answer to close this question.

Thank you and have a nice day!

Kerry