Philip, RS-232 standards are good to 10 metres or more depending on noise and cable specs. If you are missing bits then it sounds like you may have a timing issue. Make sure you are using a crystal because the error with a RC network is often too great for reliable comms unless you are transcieving at very slow speeds. You also have to sample the bits in the centre of the BIT time. Taking many samples towards the centre of the bit and then going on the highest ratio or a set standard ratio (say 80%) will improve things. ----- Original Message ----- From: "Philip Addicott" To: Sent: Friday, August 25, 2000 3:21 PM Subject: [PIC]: Protocols for Serial Communications > I have been working towards a stable serial link with a PC. I am not sending > a lot of data, things like date,time stamps plus the odd 6 or 8 byte codes. > However it has become pretty clear that good serial coms has a lot more to > it than banning bits in and out of a PIC, bits DO go missing or get > corrupted. It also seems that the pins for hardware handshaking are never > used so there must be protocols involved, so here are my questions. > > Is there a standard protocol or at least a guideline that one could work > from? > > Do I need to use CRC or is a xor check sum ok? > > Thanking you in advance. > Philip > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu