https://devzone.nordicsemi.com/f/nordic-q-a/19206/measure-frequencyHi all, I want to use nRF51822 (s110) to measure the frequency (0 to 5kHz) of a signal connected to an analog input. Other posts ( like this ) show that a good way to implement this is to use a combination of: A timer and a counter. The firsten-USTelligent Community 13Tue, 24 Jan 2017 10:33:15 GMThttps://devzone.nordicsemi.com/thread/74396?ContentTypeID=1Tue, 24 Jan 2017 10:33:15 GMT137ad170-7792-4731-bb38-c0d22fbe4515:984f9b7c-df02-4864-b2d3-cad79a62a366dblasco<p>Design is done using nRF51822 so I would like to stay with this. The first solution you tell me I think it would full quite fast the RAM capacity as you suggest... I don&#39;t understand the second solution. You mean to generate an interrupt when the threshold is passed and the get the actual timer value?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/74395?ContentTypeID=1Tue, 24 Jan 2017 10:27:07 GMT137ad170-7792-4731-bb38-c0d22fbe4515:29cc3a4f-b41d-4196-b215-9ccac1bb12a0Roger Clark<p>Have you considered sampling the data to RAM and using an FFT or digital filter to analyse the data. <a href="https://en.wikipedia.org/wiki/Fast_Fourier_transform">en.wikipedia.org/.../Fast_Fourier_transform</a></p> <p><a href="https://en.wikipedia.org/wiki/Digital_filter">en.wikipedia.org/.../Digital_filter</a></p> <p>Remember by the Niquist rule you need at least 2 folder oversampling and in practical terms you probably need at least 10 folder over-sampling.</p> <p>I think you&#39;d need to use an nRF52 for doing a FFT, as the RAM capacity and also processor speed (and lack of FPU) on the nRF51 would make this impractical or just very slow.</p> <p>On the nRF51, you may be able to run a digital filter by processing each sample in real time, rather than needing a buffer. But again, I&#39;m not sure if the processing power of the nRF51 would meet your needs (it would depend how complex the filter was)</p><div style="clear:both;"></div>