I'm building a project based on ATTiny85 low power sensors that transmit to a base station using cheap ASK/OOK 433.9 Mhz modules. I have two main questions for the hive mind:
(1) does anyone know/recommend a good ASK receiver that produces a usable RSSI signal?
(2) is there a recommended transmit/receive library that is more suitable for the ATTiny85 than RadioHead?
Regarding (1), I am using an OmShine RX03 at the moment. This is a good superhet receiver with a crystal LO and ceramic IF filter. It's based on a PT4301-X superhet receiver chip. This chip does provide an AGC gain control output that lets you get an idea of RSSI, but I have to tack a line onto the chip to get the signal out and the module is not designed to give the RSSI output. The gain signal is not ideal anyway, since the state of the internal attenuators can't be sensed. It's a bit of a hack and I would prefer to use a module that produces a documented RSSI output.
Regarding (2), I am successfully using a VirtualWire implementation. Despite the claims of RH_ASK, I find that the RadioHead implementation simply won't fit on an ATTiny85 with the other parts of my project. It also demands to use pins that I don't have for functions I don't need or want. I found someone who had written a bit-bash version of the VirtualWire transmitter that is working well for me and I can receive transmissions using a VirtualWire receiver, but for some reason not with a RadioHead RH_ASK receiver.
I've been looking at alternate TX/RX libraries and some features I would want that RH/VW doesn't have are forward error correction and compact implementations. On my list of things to try out is Andreas Rohner's RFTransmitter library. Are there other options I should be considering?