Modbus over RS-485 full duplex

Anybus Support Software
#1

Hi,

I’m using a HMS-EN2SE-R for Modbus over RS-485 full duplex to communicate to an engine control system. See image for settings on ECS image

I’m getting a response from the device using the specified Modbus addresses in the manual, but they don’t match up with the actual values at all, and they are all static values.Most of the values are temperatures that would change at least a degree every now and then but none of my readings change.

I’ve tweaked with the byte swapping settings to try to manipulate values, but the results are still random static numbers.If this is 4-wire 485, do I choose RS-422 as my physical standard? The RS-422 option was the only way I would get a response from the device at all and have my subnetwork light at least flash green.Are there any other settings I should look at to change?

I’ve attached my configuration and more pictures to give a better idea.Thanks for the assistance.

MG3 WECS.cfg (16.0 KB) MG3 WECS.cfx (39.5 KB)

modbus example addresses
modbus example addresses948×223 55.3 KB
WECS Modbus Old Wiring
WECS Modbus Old Wiring1198×317 28.2 KB

#2

Hello @bmcoleman,

Taking a look at the configuration it looks like you are using the modbus address register and not the register address for the starting address. In the user manual they give you 30178 you will need to subtract 30000 or 30001 to get the address the configuration will need. Typically you subtract 30001 but some device use a base 0 so you will only subtract 30000

Take a look at the example on the follow web site it provides a clear example of the register. http://www.simplymodbus.ca/FC04.htm

Deryck

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#3

Deryck,

Thank you for your help. It looks like that did the trick. I saw the addresses were all 30000 and assumed the command was 03 instead of 04. That in combination with the right address worked. Not sure what values I was reading before.

Thanks,
Blake

1 Like