I am wondering if anybody here knows the proper way to wire flow control for the RFD900 series radios.
Typically, for UART devices, you have to cross TX/RX as well as CTS/RTS.
The Pixhawk.org standard seems to agree with this notion, stating
Cables should be 1:1 to the peripheral and TX / RX as well as CTS / RTS should be crossed on the peripheral side (e.g. a radio modem would have its RX port on pin 2, TX port on pin 3, RTS on port 4 and CTS on port 5).
If you buy a pre-made cable on the RFdesign store, such as the PIXH2 to RFD900ux cable harness, when you look at the radio documentation, it is connecting CTS of the flight controller (cube in this case) to CTS of the modem.
What seems to add to the confusion is that we get significantly better performance in certain tasks like param downloads through an RFD TXMOD when we add flow control pins, but it doesn’t seem to matter if we connected CTS-CTS/RTS-RTS or CTS-RTS/RTS-CTS. We could not tell a difference between CTS-CTS/RTS-RTS or CTS-RTS/RTS-CTS, but there was a huge difference in speed compared to having no flow control.
Any insight would be much appreciated!