Low level library NRF52

Check out http://www.espruino.com/NRF52LL#reference

I'll just copy the relevant bit below:

/* Successive approximation analog-to-digital converter
  opts is {
    channels : [ {
      pin : D0, // pin number to use,
      npin : D1, // pin to use for negative input (or undefined)
      pinpull : undefined / "down" / "up" / "vcc/2",   // pin internal resistor state
      npinpull : undefined / "down" / "up" / "vcc/2",  // npin internal resistor state
      gain : 1/6, 1/5, 1/4, 1/3, 1/2, 1(default), 2, 4, // input gain -
      refvdd : bool, // use VDD/4 as a reference (true) or internal 0.6v ref (false)
      tacq : 3(default),5,10,15,20,40 // acquisition time in us
    }, { ... } ] // up to 8 channels
    resolution : 8,10,12,14 // bits (14 default)
    oversample : 0..8, // take 2<<X samples, 0(default) is just 1 sample
    samplerate : 0(default), 80..2047 // Sample from sample task, or at 16MHz/X
    dma : { ptr, cnt } // enable DMA. cnt is in 16 bit words
      // DMA IS REQUIRED UNLESS YOU'RE JUST USING THE 'sample' function
  }
  returns {
    status, // 0=ready, 1=busy
    config, // address of config register
    enable,
    amount, // words transferred since last tStart
    tStart,  // Start ADC
    tSample,  // Start sampling
    tStop,   // Stop ADC
    tCalib,  // Start calibration
    eDone    // event when GPIO changes
    eEnd     // ADC has filled DMA buffer
    setDMA : function({ptr,cnt}) // set new DMA buffer
               // double-buffered so can be set again right after tStart
    sample : function(cnt) // Make `cnt*channels.length` readings and return the result. resets DMA
  }
*/
exports.saadc = function (opts) { ... }

so...

var saadc = ll.saadc({
  resolution : 10, // <--- HERE
  channels : [ { 
   ...
    refvdd:false,   // <--- HERE