Modbus RTU - "Response not from selected slave"

[iJAF]

Disable RTU port in mapper and use this script to show what LM sees during communication in Logs tab. Change port parameters, slave id and register address as needed.

Code:

require('luamodbus')
mb = luamodbus.rtu()

mb:open('/dev/RS485', 38400, 'E', 8, 1, 'H')
mb:connect()

buffer = {}
mb:setdebug(function(msg)
 buffer[ #buffer + 1 ] = msg
end)

mb:setslave(10)

mb:readregisters(1)

mb:close()

log(table.concat(buffer))

Hello, thank you for the feedback.

I have used your script and the frame received by the master is the same from Modbus Slave software Traffic log !

The result is here:

EDIT: The frame sent is the same, but the response from the slave is a bit strange, comparing with traffic log !

---

In those requests you can see an almost successful frame at 09:57:21.

There is a byte <FF> preceding the correct answer.

this is a bit strange !