Quadrature demodulator output on GPIOs

[Reinhard]

Hi,

the product specification of the nRF51822 states the possibility to carry quadrature demodulator signals on GPIO pins. This would let one allow to observe the physical transmission before (de-)whitening etc. Is there an example project /code for this?

Thanks, Reinhard

[Øyvind Karlsen]

Hi Reinhard,

I'm not sure that I understand your question correctly, but I'll attempt to answer as best I can.

We do not route the on-air-signal before demodulation from the radio out to pins, furthermore that signal is not coded in quadrature.

The quadrature decoder is suitable for mechanical and optical sensors, as well as motors, i.e. wired interfaces. I am not sure what you want to use whitening for in this context.

Best regards,

Øyvind

[Øyvind Karlsen]

Hi,

For this context the decoder and demodulator are the same thing. We do not use quadrature decoding of our on-the-air signal, the encoding is FSK(Frequency shift keying), specifically GFSK(gaussian FSK), which is FSK passed through a gaussian filter. If you want to view this signal like it looks on the air, you can use a packet sniffer or spectrum analyzer.

More info on FSK can be found on wikipedia.