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ADC Sampling with Softdevice

Hi Everyone,

I am working on a hobby project with nRF51822 which needs me sample upto 4 signals reliably at 500Hz each at 10bit resolution. I have read through few posts in the forum([1],[2],[3]) and found that with softdevice installed ADC sampling rate drops to 1KHz(Or Is it 2KHz? As one forum post was suggesting so)

So for my requirement, I am assuming nRF51822 might not be good enough as sampling rate would drop to 1KHz/4 = 250Hz as I have four channels? I would like to know what my options are to implement this spec at 500Hz/channel?

  1. Is there way to do 500Hz/channel for 4 inputs with latest softdevice installed? (Connection Interval: 7.5ms, Slave latency: 0ms, 1 packet(<20bytes of data) of data transfer per connection interval)
  2. If I compromise on the sampling rate to 250Hz/channel(or dropping it to 8bit resolution), would I be able to reliably sample all channels with SD installed?
  3. If its No to the Question 1, is my only option to go for an external ADC with higher sampling rate and transferring data to nRF51822 via SPI?
  4. Is it better for me switch to nrf52840(Preference is still towards nRF51822)? I have PDK which I can work with for this project. I haven't searched around in the forum for ADC performance of nRF52840 with s140 SD.

Thanks in advance.

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