Sync RTU sequential reading failure

[gustavowd]

If i read sequentially two the sets of registers, the second read never return.

For example:
let rsp1 = ctx.read_holding_registers(32000, 20).unwrap();
let rsp2 = ctx.read_holding_registers(32300, 40).unwrap();

A simple thread sleep of 10 miliseconds between readings solve the problem. However, I beleive this issue should be solved.

[uklotzde]

What's the outcome if you use libmodbus instead of tokio-modbus for this particular device and invocation sequence?

[gustavowd]

It works with libmodbus. Maybe its the modbus RTU interframe space of 3,5 char that is not implemented in tokio-modbus.

[uklotzde]

For reference: 2.5.1.1 MODBUS Message RTU Framing

[uklotzde]

Adding a timeout unconditionally before and/or after each request would be a waste of time. Only the client knows if it will send a single request or a sequence of requests that require the insertion of silence intervals. The duration may also vary from device to device.

Ideas how to make this more convenient for clients through the API are welcome.