Javascript Examples §

Create a file name app.js and place it in working directory or use the Interactive Console to send the file directly (See API).

Hello World §

Let's start with outputing text to stdout with the print function.

Hardware Setup §

Javascript Code §

print('Hello from Javascript!');

Timer §

The example below uses the DigitalOut, Timer and print API. The function print is used to output information over the serial.

Hardware Setup §

Javascript Code §

var count = 0;
var intervalId;

dout = DigitalOut(PIN4); 
var val = false;

setTimeout(function cb() {
   print('one shot timer, called after 10 seconds');
}, 10000);


intervalId = setInterval(function () {

    print('interval', ++count);
    
    val = !val;
    dout.write(val);

    if (count >= 25) {
      clearInterval(intervalId);
    }

}, 1000);

print("Hello from Javascript!");

Note that execution order is:

I2C §

The example uses the I2C API to communicate with a MCP9808 sensor and print every 1 second the measured temperature.

var mcp9808 = {
  slave_address: 0x18,
  methods: {
    request_id: 0x06,
    request_temperature: 0x05
  },
  send_buffer: Uint8Array.allocPlain(1),
  receive_buffer: Uint8Array.allocPlain(2),
  frequency: 150
};

mcp9808.send_buffer[0] = mcp9808.methods.request_temperature; 

var tick;
var interval = 1000;

const sensor = i2c(I2C1); 
sensor.frequency(mcp9808.frequency); 

sensor.on('open', function () { 
  tick = setInterval(function () { 
    sensor.transfer(mcp9808.slave_address, mcp9808.send_buffer, mcp9808.receive_buffer); 
  }, interval); 

  sensor.on('data', function(data) { 
    mcp9808.receive_buffer = data;
    data[0] = data[0] & 0x1F;
    var signed = data[0] & (1 << 5) ? -1 : 1;
    var temperature = signed * (data[0] * Math.pow(2, 4) + data[1] * Math.pow(2, -4));
    var symbol = signed ? '+' : '-';
    var message = [
      'Raw data received',
      'MSB:' + data[0],
      'LSB:' + data[1],
      'Signed:',
      signed,
      'Temperature:',
      symbol,
      temperature,
      'C'
    ].join(' ');

    print(message); 
  }); 
});