debugging ModBus

[alf@emcom.no]

Hi.
I am using the Modbus master with a physical connection to the RS-485 port on the RevPi Connect.
The Modbus-part is set up, and I read the values with piTest etc.

It seems to work fine, BUT - I saw that if the slave does not answer, the values in the process-image are kept.
How can I pick up on this ?

Alf

[dirk]

Hi Alf, you have to read and reset the status values, see here under "Help! Error!"

Modbus_Master_Status
Master_Status_Reset
Modbus_Action_Status_[1… 32]
Action_Status_Reset_[1… 32]

[alf@emcom.no]

OK, so I can get the status, but when communication is restored, the read Modbus-values themselves will be updated again, right ?

[dirk]

Yes, if you have performed the reset of the Modbus communication accordingly then the values will be updated again.