Batboard

I built a copy of the UPI to use with Minitor 3, 4, and 5 pagers. I keep getting a serial communication - data transmission error. Anyone have any suggestions for this? Also, would it be possible to use a RIB as a UPI? Not sure if that can be done or not, never really taken a good look at a RIB schematic.
Thanks, Ryan

After a quick look at the RIB schematic, I don't think you'll have much luck using it with pagers. The pager UPI is simply an RS-232 to TTL level converter, and there are separate TX and RX lines going to the pager. The RIB converts the TX and RX signals from the computer serial port onto a communications bus that the radio talks on.

As for troubleshooting your UPI, the first thing to do is check and double check the wiring...common mistakes include getting the TX and RX swapped and having the wrong polarity on the capacitors on the MAX232 chip. +12V on the RS-232 side should give you 0V on the pager side, -12V on the RS-232 side should give you +5V on the pager side, and vice versa.

Andy