CRC check

Amin

Hi,

I have programmed my openIMU300ZA with INS application, the output packet is e2, 123bytes of payload, I need your help to check CRC bytes. do you have any sample code to check CRC of e2 packet?

Best regards,
Amin.

cek

https://forum.aceinna.com/topic/93/top-topics-of-common-operations-with-openimu-products, topic_2 pls check e2 packet example.

online doc also mentioned the crc in "3.6 16-bit CRC-CCITT" of https://openimu.readthedocs.io/en/latest/software/UARTmessaging.html#openimu-uart-messaging-framework

Amin

Hi,

from PDF downloaded from this link : https://readthedocs.org/projects/openimu/downloads/pdf/latest/

3.6 16-bit CRC-CCITT
Packets end with a 16-bit CRC-CCITT calculated on the entire packet excluding the 0x5555 header and
the CRC field itself. A discussion of the 16-bit CRC-CCITT and sample code for implementing the
13.4. OpenIMU UART Messaging Framework 127
OpenIMU Documentation
computation of the CRC is included at the end of this document. This 16-bit CRC standard is maintained
by the International Telecommunication Union (ITU). The highlights are:
Width = 16 bits
Polynomial 0x1021
Initial value = 0xFFFF
No XOR performed on the final value.
See Appendix A for sample code that implements the 16-bit CRC algorithm.

but there is no Appendix A and there is no example code at the end of file.

Best regards,
Amin.

Amin

from crc16.c :

uint16_t CalculateCRC (uint8_t *buf, uint16_t length)
{
uint16_t crc = 0x1D0F; //non-augmented inital value equivalent to the augmented initial value 0xFFFF

for (int i=0; i < length; i++) {
	crc ^= buf[i] << 8;
	
	for (int j=0; j<8; j++) {
		if (crc & 0x8000) {
            crc = (crc << 1) ^ 0x1021;
        }
		else {
            crc = crc << 1;
        }
	}
}

return ((crc << 8 ) & 0xFF00) | ((crc >> 8) & 0xFF);

}

may I use this code to compare received bytes count and CRC bytes?

Best regards,
Amin.

Mike Horton

There is example code in the open source python driver

Check here
https://github.com/Aceinna/python-openimu/blob/master/openimu/openimu.py

There also example code in the open source C++ driver

Check here
https://github.com/Aceinna/cpp-openimu/blob/master/OpenIMUProtoTest/cksum.cpp

There is finally embedded C-code in the open imu library source itself

Check here
https://github.com/Aceinna/OpenIMU330-lib/blob/master/Platform/Core/src/crc16.c