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

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Do you have the termination resistor jumpers in on all of the devices?

If so, you should remove them from all but the devices at each end of
the chain. I assume that is the PC adapter and the last OP7200. See the
OP7200 schematic for how to set them.

Are you sure all of the devices have a unique ID in whatever protocol
you are using? Multiple devices answering a query will cause contention
on the lines.

Mark
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