SNAP-SCM-485-422 start of message character



I have a SNAP-SCM-485-422 that I want to use to control a Yokogawa UT-150 tempature controller. In the documentation for the UT-150 it specifies the start of message character as Chr$(2). The documentation for the SNAP-SCM-485-422 says that the start bit cannot be configured but I can not find what start bit it uses.

I’m just trying to verify that the start bit isn’t going to be a problem.



Hello Andrew,

Welcome to the OptoForums!

Looking at this [U][B]UT100 series communications manual[/B][/U], specifically pages 10 & 16, I think you’re confusing:
[I]configuration settings[/I] (baud rate, stop bit, etc.) with the [I]command[/I]/packet, which you’ll build and send with your control strategy created using PAC Control.

You can set & save your module’s baud rate, etc., using [B]PAC Manager[/B] under Tools > Inspect > Communications > Serial Modules, select your Serial Module number there from the drop-down (I’m showing module 7 here), and configure as needed:

Then save that config also in [B]PAC Manager [/B]under Inspect > Status Write, choose “Store configuration to flash” and click “Send Command.”

Then you’ll use a communication handle variable in your [B]PAC Control[/B] strategy to build that [I]command[/I] (starting with the 2). Check out [U][B]this post on Comm Handles 101[/B][/U].

When you build your string, if you’re using OptoScript it might look something like this:

sCommand = chr(2) + chr(nUT150Address) + chr(1) + chr(0) + chr(nThisCommand) + ....

Or if you’re using regular instruction blocks, you’d use the [B]Append Character to String[/B] command:

Looks like you’ll also need the built-in [B]Generate Checksum on String[/B] command as you finish building your command/packet.

I hope that helps!