simonvetter
commented
1 year ago Hi there,
I would definitely love to add support for file and fifo opcodes. That's been on my todo list for a long, long time, I just haven't been able to do it quite yet (and get my hands on devices supporting them to test).
Regarding manufacturer-specific function codes, would adding a client method along the lines of
func (c *ModbusClient) ExecuteCustomReq(reqFC uint8, reqPayload []byte, expectedResponseLength uint8) (resFC uint8, resPayload []byte, err error)suit your needs?
The idea is that you'd send your own function code along with its payload and expected response byte length and get a reply FC back with its payload as well, a standard modbus error (if the response FC falls in the standard exception range), or any other I/O error, depending on the outcome. Both request and response payloads would be treated as opaque byte strings and the caller would be responsible for encoding/decoding them.
This should be trivial to implement for MBAP-based transports (i.e. TCP/UDP), but I'd have to find a way to let the RTU transport know about how many response bytes to expect. That may require a rework of the transport interface, but since it's not yet exposed outside of the package, it's probably okay.
Otherwise, I think it would fit nicely with the current client interface.
What do you think? BTW, are your target devices mainly TCP or RTU?
a-hennig
Shiny380
I consider switching from goburrow to this modbus stack, but would need additional FC (manufacturer, file, fifo) and vendor specific ones.
What would you think about adding an extension point for FC calls? something along the lines of wrapping assembleRTU, parseRTU, expectedResponse{length] into an interface and adding registerFC + send + receive functions to the transport or client.
this would allow me to develop my vendor specific FC locally.
And if I develop a standard FC (like one of my team members did in github.com/debevv/modbus for FC43), I can develop ahead and open a pull request to here ... without waiting on my fork until the merge is done.