I think I've mentioned it before, but for serial protocol work I use RealTerm on Windows.
It may not be your cup of tea. There are certainly more minimalist programs to use, but for talking directly to serial protocol based devices this is the best I've found. You can see the flow control lines, view in hex or ascii, paste in hex formatted and have it send as binary bytes, get it to detect some basic message framing etc. etc. It's one of those pieces of software that you can tell it was written by technicians for technicians. https://realterm.i2cchip.com/ -- John.
