Serial PROTO questions

I’m trying to use Meshtastic to send data from an RS-232 device to a base station. I had some success last year where I used SIMPLE mode, but now found out that the base station T-Beam, which is connected via the USB cable to a windows computer, cannot accept data from the USB (from windows) to be transmitted on the serial channel.
So now I’m trying to use PROTO mode. Should it use the functions as in the example in Meshtastic-arduino?

If so, how would I send binary data which is generated by my RS-232 device (but which I have source-code to, and thus I could base64 the data).

Are there any examples other than the text transmission in the above-mentioned example?

I saw a clue in the firmware source-code [SerialConsole.cpp, line 66] that the USB interface can input and output PROTO data. Can somebody confirm that?

Thanks!