On Wednesday, September 3, 2014 12:00:10 PM UTC+3, Peter Otten wrote: > dream4soul at gmail.com wrote: > > > > > calc_crc(b'\x00\x00\x34\x35\x38\x35') > > > > > unsigned char a[]={0x30,0x30,0x34,0x35,0x38,0x35}; > > > > The first two bytes differ; you made an error on the input. Dear Peter, my apologies it's my mistake. Thank you for help. Problem solved