Is possible to use MODBUS/RS485 of KNOT as a RS232 Serial port, and use it as a Serial Terminal?
The goal
Is to connect to equipment that relies solely on RS232 serial interfaces for interaction and automation, doing so via an LTE (or 5G) connection.
P.S.: The LtAP LTE7 kit seems to fit the requirements; however, it appears to be scarce on the market, and it is built using CPU and chips that seem to be nearing the end of their lifecycle.
Furthermore, it is expensive. For the same price, I could buy a ruggedized industrial-grade device and run Linux on it to handle the required tasks.
That is why it was ruled out.
To preempt potential suggestions:
No! Using a USB-to-Serial converter with a "standard" RB does not meet the project requirements.
No! Using a USB modem does not meet the project requirements.
Please focus on the issue of the GPIO port or the MODBUS port being used as RS232 within RouterOS. Is it possible or not?
But curious though is that it does let assign modbus as a /system/console. I don't have any modbus things to analyze what happens... but AFAIK providing a "serial console" is not how modbus works.
The KNOT RS485/MODBUS interface is a regular UART, the big difference is that line interface is half-duplex controlled by the UART handshake or some other CPU-controlled I/O pins.
Protocols utilising an interface like this are designed either with a master device initiating communications with the recipient responding a set time interval after receiving a message from the master, or by listening to what they send on the bus to detect collisions so they can retry some time later.
If the KNOT hardware automatically enables the RS485 drivers whilst the UART is transmitting data and the device at the other end can likewise control the TX/RX mode of an RS232/485 converter it might work as long as the two end do not send data at the same time - unlikely for generic terminal access.
