Watlow F4 Modbus 1.1.5.39 Error 38

[SciManStev]

I am trying to communicate to a Watlow F4-SH temperature controller with the latest Modbus API I could find. I can not establish any communication with the controller. I have tried RS232, and RS485 - 2 wire, as described in the Watlow manual. i even tried the Watlow F4 LabVIEW drivers, which did give me errors, stating the controllers name, so I know I have communications, but the drivers were not compatible with the F4 version I have.tried the other Modbus library, and kept getting time outs. With this newer library, I get Error 38. RTU Data Unit.lvclass:Read ADU Packet.vi 5030001. I have tried everything I can think of, and the error is the same. the two functions I am trying to use are writing to a single holding register, and read from input registers. I feel that if I can actually establish communication with the controller, I will be just fine. Any help would be most appreciated.

[cody_a]

Can you post a screenshot of your code?  What versions of all involved software are you using?

[SciManStev]

The problem was with the serial decoder in the chamber. I realize that Modbus 1.1.5.39 is not supported by National Instruments, and was ready to pay the $500 for the Modbus toolset that is supported. Many things were attempted, but in the long run, the RS232 decoder wasn't working in the chamber. I have switched to GPIB, and finally can create the drivers to do some basic functions. These I am creating with simple VISA Write and Read statements. I am still sending a register a particular value, but it is in a string format that the GPIB to RS485 decoder is thranslating into Modbus commands.

Thank you for your reply!