op7200 serial to USB connector

Rabbit
1

Hi,

I am a newbie in device programming.

I am using OP7200 device which has rabbit 2000 microprocessor.

I have a setup in which we connect 4 op7200 device to RS485 and to the other end of RS485 we connect RS232 and to the other end of RS232 we have an USB connected to the computer.

I am using WIN XP service pack 2.

I wrote a java Program using Java Comm API, which uses RXTX native library to read/write data from serial ports.Our job is to read data alone.

I am able to get Data from 3 devices(OP7200) thought serial port.

Once the fourth device is connected with RS485,we are getting framing error and junk data is read by the java program.

I tried with a C++ Program also , it is the same case.

I also tried with a commecial serial port monitor software also,no use still i am getting junk if the fourth device is connected.

Any help is appreciated.

Thanks & Regards
Gajendran.G

2

I assume you have probably solved this by now anyway.

But i had a similiar issue (not rabbit proccessor, just the rs485 problem). I think the more devices you have on the line the less it will tolerate poor/incorrect wiring.

Make sure your wiring has as physically short branches as possible and try adding termination resistors at the ends if you still have issues. I had a system with 4 rs485 meters and with the termination i could get any 3 to work but adding the 4th would stop all of them. With termination everything worked okay.