POSIX Serial Programming
I’ve been working on a cross platform Modbus communications library and driver over the last month or so. It involved a number of communication transports – tcp/ip, direct serial port and modem connected serial port. There were a number of subtle differences in the Linux implementation of serial port interaction that threw me for a bit. The following document was a great help for anything to do with unix, linux, serial port, modem communications and the various esoteric ioctl and fcntl calls you can make (now there’s a bunch of keywords I hope will be useful in the future).
http://www.easysw.com/~mike/serial/index.html
Its a pain working with serial RS232 communications these days. You can no longer go down to the local electronics store and expect to be able to buy a range of RS232 cables, connectors and breakout boxes. Its pretty much a dead technology for the mainstream – but I expect it will still be around in the SCADA industry for a while. The worst part is that there are so many combinations to deal with: 9 pin, 25 pin, male connectors, female connectors, dce/dte, various pin out options and then multiply those combinations with the two sides of the cable. Its frustrating sitting there with half a dozen different cable types and a couple of convertors, but knowing none of the combinations are what you actually need!