Category Archives: Node.js

Getting started with Minnowboard MAX

Update October 12, 2015

MRAA 8.0 and UPM 4.0 have been released recently. These releases offer improvements in both stability and, in the case of UPM, an increase in number the sensors supported. I have updated this post to install the latest versions of this software.

End Update.

After recently receiving my Minnow Board Max  (MBM)  I found that there are few good resources for getting started with it. Unlike the BeagleBone Black I have used before, the MBM does not have a 4GB eMMC that we can program by flashing a prebuilt OS image. Instead we need to use one of the external connectors to provide storage for the OS. We have a choice of using a mini SD card, USB storage, or a SATA2 device. I chose to use an 230 GB OCZ Vector on the SATA port.

The beauty of the MBM is that it is essentially a low powered X64 compatible computer. This opens up many options for OS that we can use. Since I have such a large SSD on the system I chose to dual boot Windows and Linux. I put Windows 8.1 on just because I could, not because I have any plans to develop with it. Surprisingly, 64 bit Windows runs pretty well on the MBM — not nearly as laggy as I expected. But Windows heavily loads the MBM making it run hot compared to running it with Linux. Complete instructions for installing Windows 8.1 on the MBM can be found here.

For my needs Linux is a better choice. I want to be able to take advantage of the MRAA and UPM libraries as well as have a desktop OS on the board. Since we only have 2 gigs of memory on the MBM I want a distro with a very lightweight window manager. I also want to use Ubuntu as I have a long history with it (plus I am not that crazy about Yocto anyway). This lead me to Xubuntu — an Ubuntu distro that utilizes the XFCE window manager. I chose to use version 15.04.

To get the system I am looking for I will be following these steps:

  1. Update BIOS
  2. Install OS
  3. Install Nodejs
  4. Compile and install SWIG 3.0.7.
  5. Compile and Install MRAA 8.0
  6. Compile and install UPM 4.0

Update BIOS: 

My board shipped with version 0.80 of 64 bit BIOS.  As of 9/10/15 the latest bios is 0.82, which can be found here. I used MinnowBoard.MAX.FirmwareUpdateX64 for the update. Instructions for updating using the MBM Flash Utility can be found here.

Install O/S

Xubuntu 15.04 can be downloaded here. Be sure to get the 64 bit version. The image can be burned to a DVD or put on miniSD or thumb drive. The Ubuntu site has some detailed instructions for setting up install media. I chose to copy the Xubuntu image to a thumb drive for the install. The instructions for installing are here – they describe 14.04 but work for 15.04 as well. When complete you should go ahead and do all the updates before proceeding.

Install Nodejs:

Nodejs is available in the Ubuntu repositories, but that version will not work if we try to compile MRAA nor will it allow us to install the version of MRAA that is in NPM. There are a couple of options to get around this. We can use the Nodesource PPA and use APT or we can just download the tarball from the Node site.

The instructions for using the Nodesource PPA are here. Even though they specify 14.04, the instructions are valid for 15.04 as well.

I will use the tarball from the Node site.

It’s a simple install if we use the compiled download so I downloaded the  0.12.x  version of node. The read me in the archive details the install, but it can be difficult to decipher so I will summarize here. All we need to do is copy the files from the archive to /usr/local in the file system. We can accomplish this as follows:

cd /usr/local
sudo tar --strip-components 1 -xzf /path/to/node-v0.12.7-linux-x64.tar.gz

Or use whatever tool you are comfortable with to copy the files to the correct directories. A favorite tool of mine is Midnight Commander (which can be installed via APT).

Since we are copying the files onto the system we will need to set the NODE_PATH environment variable ourselves. This can be done by editing the /etc/environment file. Add the following line to the file:

NODE_PATH="/usr/lib/node_modules"

We need to get the change picked up by the environment. To do so enter:

 sudo source /etc/environment

Alternatively you can reboot the device. If you see node related errors later, check to make sure the environment is set correctly.

Install SWIG

SWIG needs to be installed if we are going to build MRAA. SWIG has a dependency of Perl regular expressions. Install the the needed files as follows:

sudo apt-get install libpcre3 libpcre3-dev

Then download SWIG 3.0.7 from here. Detailed build instructions can be found here. Download and decompress the SWIG source files. Change to the root of the SWIG source and run the following commands:

./configure
make
sudo make install

Install MRAA:

We need build MRAA so that we can take advantage of the Python and Java bindings as well as Node. Detailed build instructions can be found here. I will summarize the steps I followed:

First – install the perquisites. This includes a Java SDK, python dev modules, cmake and git.

sudo apt-get install python-dev python3-dev cmake git

Version 8.0 of MRAA requires JNI 8, so we need to install oracle java. Instructions for doing so can be found here. (The page may look a little funny because I chose the https address). Just follow the install instructions and  test to ensure Java 8 JDK is installed.  The Java home environment variable should be set during the install. If not set it by editing the /etc/environment again by adding JAVA_HOME. Add this line to /etc/environment:

JAVA_HOME="/usr/lib/jvm/java-8-oracle"

To ensure the JAVA_HOME setting is picked up run ‘sudo source /etc/environment’ (or reboot).

Next we need to clone the MRAA repo from git hub:

git clone https://github.com/intel-iot-devkit/mraa.git

Now we are ready to build. We will used the same out of tree build as described in the MRAA documentation.

mkdir build
cd build
cmake .. -DCMAKE_INSTALL_PREFIX:PATH=/usr -DBUILDSWIGJAVA=ON
make
sudo make install

Install UPM:

UPM can be cloned with the following:

git clone https://github.com/intel-iot-devkit/upm.git

We will again be using the out of tree build as described in the documentation. Enter these commands to build and install:

mkdir build
cd build
cmake .. -DCMAKE_INSTALL_PREFIX:PATH=/usr
make 
sudo make install

Testing:

There are several examples installed in /usr/share/mraa/examples that can be used to test our installation with. These can be copied to a directory we have write access to and modified to test our set up. Be sure to use the MRAA numbers for the MBM pinouts when connecting devices to the system.

Other options:

I chose a Linux setup that worked for me, but there are other options that could be used. There are several options described on the web at Minnowborad.org using different distros of Linux, 32 bit versions of the firmware and alternate BIOS firmware.

So there it is. Hopefully this post will save you some time in getting your MinnowBoard Max configured for use. It took me a couple of days to gather all the info I needed to get my setup working. Feel free to hit me up if you have any questions or found something I did wrong.

Using a Rotary Encoder on Intel Edison, XDK

Rotary Encoders are supported by the UPM library. There is already example code that can be leveraged when we want to use one.  The code was created for the Grove Rotary Encoder but in reality we can use it for any rotary encoder we choose to implement. The Grove encoder  would be a good choice if you are using Seed Studio’s Grove Starter Kit. But that could be a problem if we wanted to use the encoder on and Edison project for the mini breakout board or wanted to access the switch in the encoder (you can not access the switch in the Grove Encoder). In my case, I intend to use the encoder to drive a menu for controlling an Edison on a mini breakout board. To accomplish that I will need to have access to the encoders built in switch so I will roll my on implementation.

Since we are going to use the Grove library for the encoder we will implement ours like theirs. If we look at the schematic for the Grove encoder we can see that it is not really that complicated.

Grove Encoder Schematic

Grove Encoder Schematic. Don’t connect  4 and 5 of the switch this way.

We can also see why the switch is not available on the Grove device – not enough pins available on the connector. (Though it does look like activating the switch will pull SIGA down, which we could look for in code. But the UPM library for this doesn’t have any provision for it.) We will wire up our encoder this way but we will wire the switch a little differently.

For the switch we will wire it so the we get a high value when it is actuated. So pin 4 goes to ground via a 10k pull down resistor and to the signal in for our Edison. Pin 5 will go to VCC.

So we need:

1     Encoder — I used these: 360 Degree Rotary Encoder w Push Button

1     Ceramic Disk 100 nf Capacitor (that is 0.1 micro farads, marked 104 on the cap).

4     3.3k Resistors. I used 2% 1/4 watt.  

And for the switch:

1     10k Resistor – also 2% 1/4 watt.

Optionally:

1     Arduino stackable header.  I plugged the encoder into this so it would fit in a breadboard better.

Wiring it up on a bread board gives us something like this:

Wired to a bead board side view

Side view

IMG_20150814_175210

Overhead view

Connected to an Edison Arduino.

Connected to an Edison Arduino board.

I used my Edison Arduino Board to prototype this, so the connections are:

SIGA —> D2

SIGB —> D3

Switch ( encoder pin 4) —> D4

VCC –> 3.3 Volts.

Don’t forget the ground connection.

The code to test this is pretty simple since we are using the UPM Libraries. We will use the Grove Rotary Encoder library for, of course, the encoder. We will use the Grove Button Library for our button functionality.

We will use socket.io to monitor our encoder with a webpage. Our server code looks like this:

//Setup express 
var express = require('express');
var app = express();
app.use(express.static(__dirname));
var server = app.listen(8085);
var io = require('socket.io').listen(server);



var mraa = require('mraa'); //require mraa
console.log('MRAA Version: ' + mraa.getVersion()); //write the mraa version to the Intel XDK console

//var myOnboardLed = new mraa.Gpio(3, false, true); //LED hooked up to digital pin (or built in pin on Galileo Gen1)
var myOnboardLed = new mraa.Gpio(13); //LED hooked up to digital pin 13 (or built in pin on Intel Galileo Gen2 as well as Intel Edison)
myOnboardLed.dir(mraa.DIR_OUT); //set the gpio direction to output

//Require the encoder and button libraries. 
var rotaryEncoder = require("jsupm_rotaryencoder");
var groveSensor = require('jsupm_grove'); 
// Instantiate a Grove Rotary Encoder, using signal pins D2 and D3
var myRotaryEncoder = new rotaryEncoder.RotaryEncoder(2, 3);
//Set up a button on D4
var button = new groveSensor.GroveButton(4); 
 
//We will send data to our client with this object. 
var data = {}; 

//When we get a socket connection we will monitor the switch. 
io.sockets.on('connection', function (socket) {
 
 //Every 100 milli seconds we will send an update to the client. 
 //You won't want to monitor encoder this way for a real project
 //but it will demonstrate the encoder and switch. 
 setInterval(function () {
 //See what the switch value is.
 readButtonValue(); 
 //Sample the current position of the encoder. 
 //Since this is an incremental encoder we will
 //get increasing or decreasing int values from 
 //the encoder library. 
 data.position = myRotaryEncoder.position();
 //For the porposes of this demo, if we go lower than -40
 //or higher than 40 we will reset the encoder init to 0. 
 if(Math.abs(data.position) > 40 ) {
 myRotaryEncoder.initPosition(0);
 data.position = 0; 
 }
 //Send the position in a json encoded string. 
 socket.emit( 'position' , JSON.stringify(data));
 }, 100);

 //Toggle the on board led on or off. 
 socket.on('toggle_led', function(data){
 if(data === 'on'){
 myOnboardLed.write(0);
 } else {
 myOnboardLed.write(1); 
 }
 });
 

});

//A fuction to read our button value
function readButtonValue() {
 //If our button is pressed set the 
 //encoder init to 0. 
 if(button.value() === 1 ) {
 myRotaryEncoder.initPosition(0); 
 } 
}
 


// When exiting: clear interval and print message

process.on('SIGINT', function()

{

 clearInterval(myInterval);

 console.log("Exiting...");

 process.exit(0); 
 
});

A Github repo with working code is located here.

When you load this on your Edison and browse to the web page it will look something like this:

Or demo page contains a gauge the reads from -40 t- 40.

Or demo page contains a gauge the reads from -40 to 40.

Rotating the knob on the encoder clockwise will increase the reading on the dial. Counter clockwise will decrease it. Activating the button on the encoder will reset the dial to 0. If we go below -40 or above 40 the dial will reset to 0. This code is based on the socket.io demo I posted about previously.

So there we have it. Using a rotary encoder in our projects will give us the ability to add controls with out the need of using potentiometers and switches. With an encoder we can implement multi-level menus to enable our end users to configure and control our devices even if they are not connected to wifi or a usb port. Implementing a menu such as this will be the subject of an up coming post.

Implementing the MICS-VZ-89T gas sensor on Intel Edison i2c

On my current project I have the requirement to monitor indoor air quality. What is of interest are the levels of Volatile Organic Compounds (VOCs) and CO2.  There are specific thresholds that we are looking for that when exceeded should trigger an action. For VOCs it is when the concentration is greater that 0.9 ppm. For CO2 it is when the concentration is 1000 ppm above ambient out side C02 — which is generally around 400 ppm. The links above out line the dangers of these indoor pollutants. When the threshold is reached we want to start the ventilation system and optionally message a user.

When I need a sensor my first choice is to find one that implements i2c. In this case I found a good candidate for the job in the SGX Sensortech MICS-VZ-89T. The VZ89 product is a small board with a MICS SMD device integrated with an i2c controller. The board comes in both 5 volt (VZ89) and 3.3 volt (VZ89T) versions that are are easy to implement using a logic level shifter with the Edison on a mini breakout board. (For an example of using a logic level shifter you can see my article Intel Edison and I2C sensors with XDK.)

There was no driver that I could find for implementing the board with my setup so I had to roll my own. This wasn’t too hard, but I did have to break out the logic analyzer to get it right. If we examine the MICS-VZ-89T I2C Specification page  we see that the device only has two commands. These are Set ppmC02 and Get VZ89 Status. According to the MICS-VZ-89T Data Sheet the device comes calibrated from the factory so we don’t need to implement Set ppmC02. That leaves us Get VZ89 Status. The code that follows here is available in an XDK project on git hub.

To read the status we have to perform a two step process. First we write a command byte of 0x09 to register address 0x70. We follow this by writing two data bytes to the same register. I write 0x00 twice.

We then read 6 bytes immediately after writing the command byte. The bytes are decoded as follows:

Data byte 1 = CO2-equivalent value. 
Data byte 2 = VOC_SHORT value. 
Data byte 3 = VOC_LONG value 
Data byte 4 = Raw sensor 1st byte (LSB). 
Data byte 5 = Raw sensor 2nd byte 
Data byte 6 = Raw sensor 3rd byte (MSB).

To implement the functionality I created the following class in a node module:

//Import mraa 
var mraa = require('mraa');

//Constructor -- set defaults and populate tx_buf
function VZ89(bus , address){

 this.bus = new mraa.I2c(bus || 1); 
 this.bus.address(address || 0x70); 
 
 this.tx_buf = new Buffer(3); 
 this.tx_buf[0] = 0x09;
 this.tx_buf[1] = 0x00;
 this.tx_buf[2] = 0x00; 
 
}

//Add a function to get the device readings. 
VZ89.prototype.getReadings = function() {
 this.bus.frequency(mraa.I2C_STD);
 this.bus.write(this.tx_buf); 
 return this.bus.read(6);
 
};
//Export as a node module 
module.exports = VZ89;

The MRAA library is used to access the i2c bus, so it is imported at the top or the file. There is a constructor that optionally takes a bus number and a devices address. The VZ89 is addressed at 0x70 so we don’t really need to change that. If the Edison mini-breakout is used we have a choice of busses. I have set this to bus 6 as I am using the Edison Arduino for this example.

A class function is added to implement named getReadings to perform the measurements and return data from the device. In this case the buffer is passed back to the calling program for use.

To use the class the code in the server file would look like this:

//Import our sensor file from the file system
var Sensor = require('./VZ89.js'); 
//Create an instance of the sensor object. 
var sensor = new Sensor();
//Create a var for the receive buffer.
var rx_buf; 

//Call the readBuf function every minute. 
setInterval(readBuf , 60000); 

//A function to read the sensor data, perform data conversions and display on the console every minute.
function readBuf(){

    rx_buf = sensor.getReadings();
 
    console.log("Co2_equ: " + ((rx_buf[0] - 13) * (1600/229) + 400) + " ppm"); 
    console.log("VOC_short: " + (rx_buf[1])); 
    console.log("tVOC: " + (rx_buf[2] * (1000/229)) + " ppb"); 
    console.log("Resistor Value: " + 10 * (rx_buf[3] + (256 * rx_buf[4]) + (65536 * rx_buf[5])) + " ohms"); 
}

The details of converting the rx_buf data to usable values are in the data sheet.  The ones we are most interested in are Co2 equivalent (rx_buf[0]) and total VOC (rx_buf[2]).

As you can see, the MICS-VZ89T is a pretty easy to use device once you know how. There are only a couple of gotchas to be aware of. First, the device can only be polled once a second. I find if I try to get the readings faster than that the device will return nulls. Secondly, care must be taken when handling the device. It contains organic material that is susceptible to solvents.