With a bit more research under my belt, my questions come down to:
- If I have a simple FSK transceiver that has 3.3v or 5v logic level for transmit and receive, is it possible to interface this with Direwolf through GPIO or the soundcard? and,
- What would be the best way to do this?
On Direwolf:
I am running under assumptions here, but it appears that Direwolf for 9600 (and above), sends and receives squarewave on the soundcard and doesn't use the GPIO pins, so all I may need is a buffer and voltage level converter and it should work. It would be nice if there was a way to directly use GPIO pins on a Raspberry Pi and not require all that extra circuitry and overhead of a CPU based DSP in Direwolf, but it's not the end of the world if that's the easiest way to test if this will work.
On the RFM23BP:
It uses the Silicon Labs Si443x chip, they have an application note, AN463, which describes bypassing internal packet handlers and going direct to raw mode.
Essentially this turns the RFM23BP (433 model), into a low cost, 1W, 70cm, FSK transceiver. Potentially compatible with other amateur radio transceivers.
I also found another datasheet, specifically for the Si4431, which does specify the receiver filter parameters to set the chip, which align with some of the G3RUH modes; like 9k6 baud with 4.8k deviation, 19k2 with 9.6k dev, 38k4 with 19.2k dev and so on.
73,
vk3tst
