Open Hardware RC Receiver

I am trying to build my own flight controller hardware to run PX4, and would really like to integrate the RC receiver directly onto the circuit board. In my searches so far, I have not found any open hardware schematics for any RC receiver. Has anyone had any luck with this or know where I can find any resources? I am open to any of the protocols that PX4 supports, with a slight preference to DSMX Spektrum.

The only somewhat hopeful thing I have found is the Crazybee F3 All in One flight controller. ( They have different versions with built-in DSMX (Spektrum), FrSky, or FlySky. I know these flight controllers don’t run PX4, but the fact that they have integrated RC receivers is hopeful because if they can do it, I might be able to as well. But I have not been able to find any documentation on how to do this.

Any suggestions would be greatly appreciated.

I’m not aware of any open receiver, there is however an open Transmitter.
The 4in1 mutliprotocol tx. It has 4 different tx chips and can do a lot of protocols. (including DSM2 and DSMX)

That might give you some hints to what receiver chip you need and the code that the tx uses might give some insight to what code to tun on the rx.