S
Hi there.
I'm new to MODBUS communications and would like to enquire something.
I'm trying to set up comms from a PLC to a Variable Frequency Drive using MODBUS protocol. On the PLC I have RS232 and on the VFD I have RS485 which I have running through a RS232 to RS485 serial converter from MOXA.
The PLC is setup using MODBUS RTU protocol and I'm trying to output a word to a parameter on the VFD. The VFD only has RS485 built-in and on the spec sheet the address I'm looking at is 0x0505.
The PLC has a message frame monitor function where I can read the messages transmitted and received to and from the drive. However, only messages from the MODBUS master (which is the PLC) show up with the following message:
SOH EOT NUL FF NUL SOH
SOH EOT ENQ ENQ NUL SOH ! BEL
The MODBUS parameters are setup the same (Parity, Stop bits, etc) but I am not receiving any comms back from the slave which is the VFD).
Is this setup incorrect or am I not able to communicate this way at all?
I appreciate your assistance.
Shandene
I'm new to MODBUS communications and would like to enquire something.
I'm trying to set up comms from a PLC to a Variable Frequency Drive using MODBUS protocol. On the PLC I have RS232 and on the VFD I have RS485 which I have running through a RS232 to RS485 serial converter from MOXA.
The PLC is setup using MODBUS RTU protocol and I'm trying to output a word to a parameter on the VFD. The VFD only has RS485 built-in and on the spec sheet the address I'm looking at is 0x0505.
The PLC has a message frame monitor function where I can read the messages transmitted and received to and from the drive. However, only messages from the MODBUS master (which is the PLC) show up with the following message:
SOH EOT NUL FF NUL SOH
SOH EOT ENQ ENQ NUL SOH ! BEL
The MODBUS parameters are setup the same (Parity, Stop bits, etc) but I am not receiving any comms back from the slave which is the VFD).
Is this setup incorrect or am I not able to communicate this way at all?
I appreciate your assistance.
Shandene