This leads me towards the conclusion, that my C Legato App is actually communicating in RS232 mode despite having tried to set the rs_mode to RS485. And that, for whatever reason, the serial port is still silent when in rs485 mode.
I feel like I’m on the edge of overstepping some bounds, but if you can buy, borrow, or hack an Arduino to be a logic analyzer, it’s the difference between spending a week discovering that you’re actually in RS232 mode, or having it fixed within minutes. If you get one with an analog input it can also be useful for power profiling. They really are that useful. The Saleae ones are are really nice.
It sounds like you have been communicating successfully with various rs485 devices, are you able to confirm that?
I’ve only tried a single sensor so far. The port is definitely switching into RS-485 mode. I’m going to add a second device in the next few weeks, I’ll post here if I run into any trouble with it.