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Eurotherm RS232 El-Bisynch Communication

Question asked by Lars on Aug 5, 2011
Latest reply on Aug 5, 2011 by Lars

I find my self a bit lost at the moment. I'm trying to communicate from my Vee application with an Eurotherm temperature controller. As protocol I intent to use the propriatary Bisynch via an RS232 port instead of Modbus for the ease of use (at least I hoped so). My Vee Version is 9.22. The Agilent Connection Expert is 16.1. I try to access the Instrument via a Direct I/O ASRL device.

The Bisynch RS232 communication requires RS232 to be set in this case to 19.2k Baud, 7Bit, LSB, Parity=Even, Stop Bit=1. I have configured speed, data width and so on via the Connection Expert and LSB in the advanced device options under Vee.

An example data request would look like (Hex): 04 30 30 31 31 50 56 05
The expected response would look like (Hex): 02 50 56 56 ?? ?? ?? 03 ??

If I send the request directly to the serial port via a terminal application I receive the expected response. Response time is max 10ms.

When I send the request via a Direct I/O Object (as Text or Binary) I can see the correct Hex values being send via the I/O Monitor. But I can catch no response from the serial port regardless of what I try. I always get a timeout. Somehow I must be missing some crucial part here.

With best regards, Lars Sölter