Endless loop in modbus_crc16?

[etet100]

I had a problem running GRBL in simulator mode. It turned out that the code crashes in modbus_crc16x. This function allows length up to 16 bits but the counter (pos) is 8 bits. Is this intentional? In my case, len is 420 and the loop never ends.

[terjeio]

Is this intentional?

Yes, max message length is 256 bytes including the CRC, from MODBUS APPLICATION PROTOCOL SPECIFICATION v1.1:

RS232 / RS485 ADU = 253 bytes + Server address (1 byte) + CRC (2 bytes) = 256 bytes.

[etet100]

I understand. But this function also has an alias calc_checksum.

#if NVS_CRC_BYTES > 1
#define calc_checksum(data, length) modbus_crc16x(data, length)
#else

while calc_checksum is used to check the configuration object, which has 420 bytes.