Hi Matt. I'm about to start a similar exercise so am quite interested in your result= s. Is yours similar to the one at ?? It would seem to have very similar capabilities. Richard P 2010/1/13 Matt Callow : > Hi, > > I've been trying to decode the signals from an RF temperature and > humidity sensor. The sensor is a small battery powered sensor which > comes as part of an home 'weather station' > The messages are all 36 bits long, I've worked out most of it, but it > looks like there may be a 4 bit checksum or crc at the end, which I > have been unable to work out. > > Here are some examples, with the information I know. Each message > contains a ID (which changes every time the sensor is reset and it > used to 'pair' the sensor to the display unit), =A0channel id, 12 bit > signed temperature reading and humidity as 2 BCD digits. I think the > last 4 bits are some sort of checksum/crc > > This is what I know of the protocol so far > > ID?=A0 CH ?????? Temperature =A0Humidity =A0CRC? > 0001 01 001010 010100110000 1100 0010 1100 > 0001 10 001010 111100110000 0010 0010 0111 > 0001 11 001010 011100110000 1100 0010 0111 > 0001 10 001000 111000110000 0010 0010 0101 > 0001 10 001000 000100110000 0010 0010 1001 > 0001 10 001000 100100110000 0010 0010 0001 > > I think the bits marked ?????? include battery level, and I'm not sure > what else. > > I have lots of data, so I'm thinking that it should be possible to > work out the CRC algorithm, however I've tried various crc calculators > such as http://www.lammertbies.nl/comm/info/crc-calculation.html but > have not been able to find the crc parameters. > > I've also tried crcbfs.pl to find the crc parameters, however this > method requires that I have at least 2 strings of different lengths > (which I don't have). > > Does anyone have any suggestions of how I might work out this CRC (if > indeed it is a CRC)? > > Regards > > Matt > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist