Node-picap NPM

node-picap

Node module for interfacing with the MPR121 on the Bare Conductive Pi Cap.

Installation

This library requires Node.js v6.7.0 or higher and also requires that the Bare Conductive MPR121 Wiring Pi Library be installed.

If you're using a Raspberry Pi, this is most easily achieved by running

sudo apt-get install picap

which will install this module along with lots of example code and setup utilities that will help you get the most out of your Pi Cap.

If you're a masochist, start with

npm install node-picap

Usage

Simple Touch example

var MPR121 = require('node-picap');
var mpr121;

// correct address for the Pi Cap - other boards may vary
mpr121 = new MPR121('0x5C');

mpr121.on('data', function(data) {
  data.forEach(function(electrode, i) {
    if (electrode.isNewTouch) {
      console.log('electrode ' + i + ' was just touched');
    }
    else if (electrode.isNewRelease) {
      console.log('electrode ' + i + ' was just released');
    }
  });
});

Datastream example

var MPR121 = require('node-picap');
var mpr121;

// note that interval sets the interval (in ms) at which 
// the module attempts to emit data events - the MPR121 
// hardware sets a lower limit on this - default is 10ms, 
// can set down to 1ms
mpr121 = new MPR121('0x5C', { interval: 10 });

mpr121.on('data', function(data) {
  // split out each of the various data streams...
  var touch = data.map(function(electrode) { return electrode.isTouched ? 1 : 0; });
  var tths  = data.map(function(electrode) { return electrode.touchThreshold; });
  var rths  = data.map(function(electrode) { return electrode.releaseThreshold; });
  var fdat  = data.map(function(electrode) { return electrode.filtered; });
  var bval  = data.map(function(electrode) { return electrode.baseline; });
  var diff  = data.map(function(electrode) { return electrode.baseline - electrode.filtered; });

  // ...and send them out via stdout - simples!
  console.log('TOUCH: ' + touch.join(' '));
  console.log('TTHS: ' + tths.join(' '));
  console.log('RTHS: ' + rths.join(' '));
  console.log('FDAT: ' + fdat.join(' '));
  console.log('BVAL: ' + bval.join(' '));
  console.log('DIFF: ' + diff.join(' '));
});