pinephone_treadmill_scroller.js

// sensor via https://wiki.postmarketos.org/wiki/PINE64_PinePhone_(pine64-pinephone)#Sensors
const x_path = "/sys/bus/iio/devices/iio:device3/in_accel_x_raw"
const y_path = "/sys/bus/iio/devices/iio:device3/in_accel_y_raw"
const z_path = "/sys/bus/iio/devices/iio:device3/in_accel_z_raw"

var fs = require("fs");
var express = require('express');

var app = express();
// could be WSS but fast enough on LAN as-is
app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
  next();
});
app.get('/', function (req, res) {
  var x = Number( fs.readFileSync(x_path, 'utf-8') )
  var y = Number( fs.readFileSync(y_path, 'utf-8') )
  var z = Number( fs.readFileSync(z_path, 'utf-8') )
  res.end( JSON.stringify({x,y,z}) )
})

var server = app.listen(8081, function () {
   var host = server.address().address
   var port = server.address().port
   
   console.log("IMU data server listening at http://%s:%s", host, port)
})

/* 
// client side, could be hosted in the target page or executed in the console or as a WebExtension for example

yprev=0,zprev=0
min_squared_sum=30000000 // magic value, depends on your calibration
// phone is expected to be in your pocket with a slight forward angle
min_diff=100
as = setInterval( () => { 
  fetch('http://pinephone:8081/') // assuming you have this address in hosts
  // if content is served over https you'll have to allow mixed security or tunnel through https
      .then( response => { return response.json() } )
      .then( res => {
    
                        var moved =                       
                     //res.y*res.y + res.z*res.z > min_squared_sum,
                     //  ( Math.abs(yprev-res.y) > min_diff ),
                     //  ( Math.abs(zprev-res.z) > min_diff ),
                     (res.y*res.y + res.z*res.z > min_squared_sum
                      && ( Math.abs(yprev-res.y) > min_diff )
                      && ( Math.abs(zprev-res.z) > min_diff )
                     )
          console.log(res, moved)
                        if (moved) window.scrollBy(0, 1) // adjust based on reading and walking speed
  
          yprev=res.y
          zprev=res.z
  })
} , 100 );

*/