I found and bought the RF modules I needed for the GS-brain comms: the RF4463F30
They have a 1W PA, the receiver has -122dBm sensitivity at low data rates and around -90-96dBm at 1Mbps max rate.
They are pretty small and light – under 2-3 grams I think.
I managed to find a lot of documentation from SI and the RF chip works pretty differently than the RFM22B. It’s not programmed using registers but with SPI commands. You basically create API calls in a uint8_t buffer and send it through SPI.
The FIFO is only 64 bytes but it does have a CRC and a custom 4 byte header to pack various things – like a request id.
So far it seems very nice, I will try to make it work during the weekend.
The plan I have is to use the wifi only for video data – tx only, and the RF4463 for bidirectional commands (GS->Brain and back) and video packet confirmations.
This should allow me to use better the limited wifi bandwidth by using uni-directional comms – so the back packets don’t keep the channel busy – and also have a rock solid link for control.
I did some tests with the RFM22B at 0dBm and it can easily go through 4-5 walls and 20 meters inside my house. With 20 or even 30dBm I should be able to have a solid 10Km link line of sight.