nRF51822 (BBC Micro:bit) FSK encode and decode

[Jason RJ]

I'm looking to encode and decode an AFSK signal (via wire not RF) using 2KHz (0) & 4KHz (1) with an 8-bit frame size and 6 frames to a block. Is this achievable with the Micro:bit? Can I make use of the S110 SoftDevice in a non-bluetooth way with direct IO to the pins, or is this a job for the ADC? Any pointers appreciated.

Many Thanks

Jason

[Einar Thorsrud]

Hi Jason,

I have no experience with Micro:bit specifically, but I would think that you should be able to do this on the nRF51 on the MicroBit. The receiving part could probably use the ADC could be used to sample the signal and process it in software. For the transmitter part, I would think that you could hook a timer (or RTC) to a GPIO using PPI to generate the two frequencies, and only have to reconfigure when you change frequency (new symbol). You will probably need some external analog filtering as well.

It would be interesting if someone in the forum has done something similar or have any other ideas.