Capsense

So when you say it counts up/down 100 times between logic 1 and 0, at what frequency?

I haven't actually checked - at a guess I'd say around 8MHz. It's not entirely accurate because an IRQ could fire during it and knock it off - one of the reasons it's done 100 times.

it is using the definition of logic high and logic low for thresholds, correct?

Yes.

I just gave this a try:

var TX = D11;
var RX = D12;

var ll = require("NRF52LL");
// set up pin states
digitalWrite(TX,0);
pinMode(RX,"input");
// Source of events
var src = ll.gpiote(0, {type:"event",pin:RX,lo2hi:1,hi2lo:1});
var dst = ll.gpiote(1, {type:"event",pin:TX,lo2hi:1,hi2lo:1});
// Counter for crosses
var ctr = ll.timer(3,{type:"counter"});
// Set up and enable PPI
ll.ppiEnable(0, src.eIn, ctr.tCount);
ll.ppiEnable(1, src.eIn, dst.tOut);


setInterval(function() {
  poke32(ctr.tCapture[0],1);
  poke32(ctr.tClear,1);
  var v = peek32(ctr.cc[0]);  
  print(v);
}, 1000);

And it does do something - but looking at it with a scope for some reason there's a massive delay in the oscillation (it's only 100 times a second), which makes it basically useless. It may be you can tweak it (for instance using the comparator) to make it work better though.