RS 485 wireless communication

[Armadus]

I am using two Texas Inst. SN75176 (RS 485 Transceivers) to communicate between two PIC 18F242s via 2 wire RS 485. The system works fine with the two wires, but does not work when I replace the wires with a Aerocomm CL4490 , 900mhz, RS 485 wireless transceiver.

I have written a simple Serout and Serin program to send a decimal value (1 to 99) from one PIC to the other. The correct decimal value is displayed on a serial LCD on the recieving PIC when wired, but with the radios I always get value of 0 or 252.

Based on the radio diagnosis and factory engineers the radios appear to be set up and connected correct.

Any suggestions

[Ioannis]

Silly, but have you tried to reverse the wires (a,b) on one side?
Ioannis

[Armadus]

I have tried revesing a and b on each radio, and both radios, but do not get any data transfer when switched.

[Ron Marcus]

I have tried revesing a and b on each radio, and both radios, but do not get any data transfer when switched.

Can the 4490 be run in UART mode? If so, take the converters out of the equation, and hook the 18Fs directly to the wireless modems.

[Darrel Taylor]

Did you do the set-up of the units?

As I understand it, you have to use an RS232 to RS485 adapter and connect it to a PC to configure them for "Master/Client" and baud rate.

Master/Client? (What ever happened to the Slaves?). They take the fun out of everything these days.
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[Armadus]

I did run the set up utility for the units. I have spoke to the Aerocomm engineers and according to them the set up is correct.

I have also ran the diagnosis and using the PC interface the radios seem to be working properly.

Thanks