I have a piece of obsolete equipment that is no longer made. The company that made this thing is notoriously secret about anything technical, and there is no technical documentation available that I can find. I'm trying to make a compatible replacement of it using Arduino. The device has a "Data In" port and a "Data Out" port. Each port has 5 wires running to it, and each port has a MAX489E chip on the board. The logic on the original board is handled by a MC68HC11E1CFNE2 microcontroller, but I'll be using an Arduino instead.
The MAX489E is an RS422/RS485 chip. I need to figure out 3 things:
- Is it using RS422 or RS485?
- What baudrate is it running at?
- Which wires are used for power, data, etc? What's the pinout? How would I figure this out?
Once I figure out these things, I can build an RS4xx sniffer and put it on the bus to start documenting the protocol. Actually, if I figure out #3, I can probably figure out the other 2 by trial and error.
Here's a photo: