RS 485 wireless communication

[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

[Armadus]

RE: Uart mode

I cannot see any method to change the radio to Uart Mode using the Configuration Utility, but I will look into this.

Thanks

[Ron Marcus]

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

If the PC works, then it is your link from the 18Fs to the converters. Now, the PC has a 232 port I assume? How do you connect the PC to the 4490s? I would emulate this with the 18Fs, without the converters. I have worked extensively with 422s, but not 485 converters. I know the parallel resistor across A & B are crucial. If the 4490 system already has one, you may not need another in parallel on your board. Conversely, if it does not, you may need to add one.
You know the link works. The converters work hardwired, if you set up the 18Fs as quasi 232s and establish a link like the PCs (without the converters), all fingers point to the 485 converters. I used Maxims with no problems on my 422 projects FWIW.

Ron

[Armadus]

Ron,

Thanks for the insight.

I used a B&B electronics RS 232 to RS 485 converter to connect the 4490 to the PC.

According to Aerocomm there is no need for a terminating resistor, but I have tried a 100 ohm resistor and it made no difference.

At this time I believe that the S75176 converters and the 4490 are just not compatable. I will look into the Max converter that you mentioned.

Thanks
Greg

[Ron Marcus]

Can you hook up the PICs directly to the 232 side of the 232 to 485 converters? At least this will prove it is a problem with the TI part. It would bite if you got the Max parts and found out it was something else! I replaced every part on an RF comm board (including connectors!), to find out I mixed up the RTS and CTS lines in my code. That was five hours better spent elsewhere. "The length of time debugging is directly proportional to the stupidity of the error." This I have gleaned from personal experience.
Ron