At 09:56 AM 2/25/2006, Jesse Lackey wrote: >Hello all, I often have designs that need rs-485 with some relatively >simple microcontroller code, and it is always been a two-chip solution: >75176 (or equivalent with improvements) and a PIC of some sort. > >Does anyone know of a microcontroller with a built-in RS-485 >transceiver? Ideally it would have a UART (pretty much a necessity, but >not absolutely required), 16 pins or less, and a decent C compiler >available from the vendor or 3rd party that doesn't cost a kilobuck. >Freeware versions limited to say 4K codespace are acceptable. I've not ever seen a micro with built-in RS-232 or RS-422 or RS-485 drivers. I suspect one of the reasons is the requirement to withstand some serious electrical abuse. Couple of points: 1) I always try to use a socketed DIP RS-xxx driver in my designs - even those boards that are otherwise completely SMT. I've spent far too much time replacing blown interface chips on other people's designs. Friend of mine goes through the same thing whenever we get serious thunderstorms near our local stadium - RS422 drivers and receivers die in the Sony Jumbotron video screen. Sadly - those are so14. Easy to change but the pads get tired after several dozen replacements. 2) If all you need is RS-422 or RS-485 transmit only (no receive), bit-bang it. I've done balanced data (2 complimentary outputs) transmit at 250Kb/s (DMX) on a 4 MHz PIC. IOW - 4 instructions per bit with both output lines changing state at the same instant. PIC outputs are protected with a couple of P6KE7.5A tranzorbs. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 22 years of Engineering Innovation (1984 - 2006) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist