Generating CRSF commands using a Raspberry Pi

[szangvil]

I have a project where I want to (try and) control a racer using a computer and not an RC. As a first test, I recorded the CRSF commands going out of a BETAFPV RX unit and I can see they are all valid. When I replay those same bytes into a Betaflight controller, it ignores them. I am getting the feedback from the Betaflight configurator's Receiver screen - when the Rx is connected and I move the stick, I see all 4 channels change, when I replay the receiver's commands, nothing is moving. I made sure I was using the correct baud rate and serial UART settings.

Any ideas?