I am having trouble writing the correct data to a relay board using mbpoll.
It uses Modbus RTU, and the data that I NEED to write is: 01 06 00 01 01 00 D9 9A
The command I am using is: sudo ./mbpoll -m rtu -b 9600 -0 -t 4:hex -P none -v /dev/ttyUSB0 -1 0001
This gives me a result of:
Protocol configuration: Modbus RTU
Slave configuration...: address = [1]
start reference = 1, count = 1
Communication.........: /dev/ttyUSB0, 9600-8N1
t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, output (holding) register table
[01][06][00][01][00][01][19][CA]
Waiting for a confirmation...
<01><06><00><01><00><01><19><CA>
Written 1 references.
It is slightly off and the relay board does not respond. Any idea how I can use mbpoll to write the correct formatted data?
Thank you very much!!!!!
You need to request register 256 (PDU addressing as you have specified -0). So the following (using different port) should work:
mbpoll -m rtu -b 9600 -0 -t 4:hex -P none -v /dev/ttymxc0 -1 256
Results in:
Protocol configuration: Modbus RTU
Slave configuration...: address = [1]
start reference = 1, count = 1
Communication.........: /dev/ttymxc0, 9600-8N1
t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, output (holding) register table
[01][06][00][01][01][00][D9][9A]