JavaScript samples for the Grove Starter Kit

To follow the instructions in this guide, you should have the Intel® XDK for IoT installed, and you can successfully blink the onboard LED on your Intel® Edison.

Programming Grove components

Install code libraries

MRAA

Libmraa (pronounced “em-raah”) is a C/C++ library (with bindings to JavaScript and Python) to interface with the GPIO pins on the Intel® Galileo, Intel® Edison, and other platforms.

Intel® maintains the MRAA library on Github.

C/C++ API documentation and JavaScript API documentation can be found on intel.com.

1. Establish an SSH or serial connection to your Intel® Galileo or Intel® Edison.
   Don’t know how? Refer to Shell Access.

2. Run the following commands on your board. The first command will edit the mraa-upm config file on the board. The last two commands use the board’s built-in Opkg package manager to download and update the missing library.

echo "src mraa-upm http://iotdk.intel.com/repos/1.1/intelgalactic" > /etc/opkg/mraa-upm.conf

opkg update

opkg install libmraa0

UPM

UPM is a higher level library that leverages libmraa for controlling more complex sensors or actuators. A supported sensor will have its own class file that needs to be imported into your project and instantiated.

Intel® maintains the UPM library on Github.

For code samples, look for your specific component on software.intel.com/iot/hardware/sensors or in the examples folder in the UPM Github repo.

1. Establish a serial connection to your Intel® IoT board, if you’re not already connected.

2. Run the following command to use the board’s built-in Opkg package manager to download and update the UPM library.

   opkg install upm

Find code samples

1. To find code samples for your component, start by visiting the hardware sensors page at software.intel.com/en-us/iot/hardware/sensors.

   1. Browse for supported components by paging through the list. Filter the results using the drop down menus on the page.

   2. Click on a component to view additional information and view code samples in C/C++, JavaScript, and Python (when available).

2. Alternatively, to find the most up-to-date UPM code samples, browse the UPM “examples” folder at github.com/intel-iot-devkit/upm/tree/master/examples.

   1. Go into the “c++”, “javascript”, or “python” folder and look for your component by model or part name.

Grove component types

The simpler components in the Grove Starter Kit fall into 2 categories: input or output. These two categories further subdivide into digital or analog.

Other components in the Grove Starter Kit may use more complex communications protocols such as UART or I2C.

Identifying which category a component falls under is required in order to correctly attach the component to the Grove Base Shield and to understand what code library and commands are needed to control the component.

Digital outputs

Example components:

• Grove LED Socket Kit
• Grove Smart Relay

Low level MRAA-only example:

var mraa = require('mraa');

var led = new mraa.Gpio(6);      // set up GPIO digital pin #6
led.dir(mraa.DIR_OUT);           // set the GPIO direction to output
led.write(1);                    // set the digital pin to high (1)

If you want to make the LED turn on and off, add a setTimeout() or setInterval() to toggle between writing 1 or 0 to the digital pin. For example:

var blinkState = 0;              // keep track of LED state

function blink(){
  led.write(blinkState);
  blinkState = blinkState?0:1;   // toggle state
}

setTimeout(blink, 1000);         // toggle the on board LED every second

Higher level UPM example:

var groveSensor = require('jsupm_grove');

var led = new groveSensor.GroveLed(6);   // set up GPIO digital output pin #6
led.on();                                // set the digital pin to high

Digital inputs

Example components:

• Grove Button
• Grove Touch Sensor (TTP223)

Low level MRAA-only example:

var mraa = require('mraa');

var button = new mraa.Gpio(5);     // set up digital read on digital pin #5
button.dir(mraa.DIR_IN);           // set the GPIO direction to input

var buttonState = button.read();   // read the value of the digital pin
console.log(buttonState);          // write the value to the console for debugging

To react to a button press beyond application startup, add a setTimeout() or setInterval() to periodically poll the pin state. For example:

function checkState(){
  var buttonState = button.read();   // read the value of the digital pin
  console.log(buttonState);          // write the value to the console for debugging
}

setInterval(checkState, 500);        // poll for changes in state ever 1/2 second

Higher level UPM example:

var groveSensor = require('jsupm_grove');

var button = new groveSensor.GroveButton(5); // set up digital input on pin #5

var buttonState = button.value();  // read the value of the digital pin
console.log(buttonState);          // write the value to the console for debugging

Analog inputs

Example components:

• Grove Light Sensor
• Grove Rotary Angle
• Grove Temperature
• Grove Sound Sensor

Low level MRAA-only example:

var mraa = require('mraa');

var light = new mraa.Aio(0);     // set up analog input on analog pin #0 (A0)

var lightValue = light.read();   // read the value of the analog pin
console.log(lightValue);         // write the value to the console for debugging

Higher level UPM example:

var groveSensor = require('jsupm_grove');

var light = new groveSensor.GroveLight(0); // set up analog input on pin #0 (A0)

var lightValueRaw = light.raw_value();     // read the raw value of the analog pin
var lightValue = light.value();            // read the converted value of the pin
console.log(lightValueRaw, lightValue);    // write values to console for debugging

To react to changes in light beyond application startup, add a setTimeout() or setInterval() to periodically poll the sensor value.

Analog outputs

Example components:

• Grove LED Socket Kit
• Grove Buzzer
• Grove Servo Motor (ES08A)

Low level MRAA-only example:

var mraa = require("mraa");

var led = new mraa.Pwm(3);  // initialize PWM on digital pin #3
led.write(0.5);             // make LED half brightness

The below example will fade the LED over time:

var mraa = require("mraa");

var led = new mraa.Pwm(3);  // initialize PWM on digital pin #3
var brightness = 1;
var fadeInterval;

function fade(){
  led.write(brightness);
  brightness -= 0.01;
  if (brightness < 0) clearInterval(fadeInterval);
}

fadeInterval = setInterval(fade, 100);

Higher level UPM example:

For an example using a servo motor, see https://github.com/intel-iot-devkit/upm/blob/master/examples/javascript/es08a.js

I2C

Example components:

• Grove LCD RGB Backlight (JHD1313M1)

Higher level UPM example:

var jsUpmI2cLcd  = require ('jsupm_i2clcd');
 
var lcd = new jsUpmI2cLcd.Jhd1313m1(6, 0x3E, 0x62); // Initialize the LCD

lcd.setCursor(0,1); // go to the 1st row, 2nd column (0-indexed)
lcd.write("hello"); // print characters to the LCD screen