Archive | arduino

Book – “Arduino Workshop – A Hands-On Introduction with 65 Projects”

Over the last few years you may have noticed a few of my Arduino tutorials, and during this time many people have mentioned that I should write a book. And now thanks to the team from No Starch Press this recommendation has morphed into my book – “Arduino Workshop“:

Arduino Workshop book

Now into the third print run, “Arduino Workshop” is one of the few books on the market that can take the reader from zero knowledge to understanding the Arduino development platform, and working with a huge array of add-ons and technologies. And a huge “thank you” to all those who have purchased and supported the book so far.

Arduino Workshop” offers a professionally-edited and curated path for the beginner to learn with and have fun. It’s a hands-on introduction to Arduino with 65 projects – from simple LED use right through to RFID, Internet connection, wireless data, working with cellular communications, and much more. Plus the reader also learns about electronics, good coding and other interesting topics.

Arduino_Workshop_GPS

Each project is explained in detail, explaining how the hardware and Arduino code works together. Plus we teach you how to read and understand circuit schematics and use this clear method of describing circuits which prepares the read for further electronics learning.

Arduino Workshop piezo

The reader doesn’t need any expensive tools or workspaces, and all the parts used are available from almost any electronics retailer. Furthermore all of the projects can be finished without soldering, so it’s safe for readers of all ages.

The editing team at No Starch Press, our technical editor Marc Alexander and myself have worked hard to make the book perfect for those without any electronics or Arduino experience at all, and it makes a great gift for someone to get them started. After working through the 65 projects the reader will have gained enough knowledge and confidence to create many things – and to continue researching on their own. Or if you’ve been enjoying the results of my thousands of hours of work here at tronixstuff, you can show your appreciation by ordering a copy for yourself or as a gift. If you’re still not sure, review the table of contents, index and download a sample chapter from the Arduino Workshop website.

Arduino Workshop is available from No Starch Press in printed or DRM-free eBook (PDF, Mobi, and ePub) formats. And the eBooks are also included with the printed orders so you can get started immediately. Furthermore you can also find Arduino Workshop for sale from all the popular booksellers around the globe.

tronixstuff

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in arduino, Arduino Workshop, book, lesson, tronixstuff, tutorial0 Comments

Tutorial – Google Docs and the Arduino Yún

Introduction

This is the second in a series of tutorials examining various uses of the Arduino Yún. In this article we’ll examine how your Arduino Yún can send data that it captures from the analogue and digital inputs and a real-time clock IC to an online Google Docs spreadsheet. Doing so gives you a neat and inexpensive method of capturing data in real-time and having the ability to analyse the data from almost anywhere, and export it with very little effort.

Getting Started

If you haven’t already done so, ensure your Arduino Yún can connect to your network via WiFi or cable – and get a Temboo account (we run through this here). And you need (at the time of writing) IDE version 1.5.4 which can be downloaded from the Arduino website. Finally, you will need a Google account, so if you don’t have one – sign up here.

Arduino Yun Yún front

Testing the Arduino Yún-Google Docs connection

In this first example we’ll run through the sketch provided by Temboo so you can confirm everything works as it should. First of all, create a spreadsheet in Google Docs. Call it “ArduinoData” and label the first two columns as “time” and “sensor”, as shown in the screen shot below:

Arduino Yun Google Docs Spreadsheet

Always label the required columns. You can call them whatever you need. For new Google users, the URL shown in my example will be different to yours. Next, copy the following sketch to the IDE:

Now look for the following two lines in the sketch:

This is where you put your Google account username and password. For example, if your Google account is “[email protected]” and password “RS2000Escort” the two lines will be:

Next, you need to insert the spreadsheet name in the sketch. Look for the following line:

and change your-spreadsheet-title to ArduinoData. 

Finally, create your header file by copying the the header file data from here (after logging to Temboo) into a text file and saving it with the name TembooAccount.h in the same folder as your sketch from above. You know this has been successful when opening the sketch, as you will see the header file in a second tab, for example:

Arduino Yun sketch header file

Finally, save and upload your sketch to the Arduino Yún. After a moment or two it will send values to the spreadsheet, and repeat this every sixty seconds – for example:

Arduino Yun Google Docs Spreadsheet data

If your Yún is connected via USB you can also watch the status via the serial monitor.

 One really super-cool and convenient feature of using Google Docs is that you can access it from almost anywhere. Desktop, tablet, mobile… and it updates in real-time:

Arduino Yun_ Google Docs Spreadsheet_data_mobile

So with your Yún you can capture data and view it from anywhere you can access the Internet. Now let’s do just that.

Sending your own data from the Arduino Yún to a Google Docs Spreadsheet

In this example we’ll demonstrate sending three types of data:

With these types of data you should be able to represent all manner of things. We use the RTC as the time and date from it will match when the data was captured, not when the data was written to the spreadsheet. If you don’t have a DS3232 you can also use a DS1307.

If you’re not familiar with these parts and the required code please review this tutorial. When connecting your RTC – please note that SDA (data) is D2 and SCL (clock) is D3 on the Yún.

The sketch for this example is a modified version of the previous sketch, except we have more data to send. The data is captured into variables from the line:

You can send whatever data you like, as long as it is all appended to a String by the name of rowdata. When you want to use a new column in the spreadsheet, simply append a comma “,” between the data in the string. In other words, you’re creating a string of CSV (comma-separated values) data. You can see this process happen from the line that has the comment:

in the example sketch that follows shortly. Finally, you can alter the update rate of the sketch – it’s set to every 60 seconds, however you can change this by altering the 60000 (milliseconds) in the following line:

Don’t forget that each update costs you a call and some data from your Temboo account – you only get so many for free then you have to pay for more. Check your Temboo account for more details.

So without further ado, the following sketch will write the values read from A0~A3, the status of D7 and D8 (1 for HIGH, 0 for LOW) along with the current date and time to the spreadsheet. Don’t forget to update the password, username and so on as you did for the first example sketch:

… which in our example resulted with the following:

Arduino Yun Google Docs Spreadsheet time date data

… and here is a video that shows how the spreadsheet updates in real time across multiple devices:

 Conclusion

It’s no secret that the Yún isn’t the cheapest devleopment board around, however the ease of use as demonstrated in this tutorial shows that the time saved in setup and application is more than worth the purchase price of the board and extra Temboo credits if required.

And if you’re interested in learning more about Arduino, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a third printing!) “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in arduino, DS3232, Google Docs, iot, spreadsheet, temboo, tronixstuff, tutorial, Yún7 Comments

Project – LED Cube Spectrum Analyzer

Introduction

A few weeks ago I was asked about creating a musical-effect display with an RGB LED cube kit from Freetronics, and with a little work this was certainly possible using the MSGEQ7 spectrum analyser IC. In this project we’ll create a small add-on PCB containing the spectrum analyser circuit and show how it can drive the RGB LED cube kit.

Freetronics CUBE4 RGB LED cube kit

Assumed knowledge

To save repeating myself, please familiarise yourself with the MSGEQ7 spectrum aanalyserIC in Chapter 48 of our Arduino tutorials. And learn more about the LED cube from our review and the product page.

You can get MSGEQ7 ICs from various sources, however they had varying results. We now recommend using the neat module from Tronixlabs.

The circuit

The LED cube already has an Arduino Leonardo-compatible built in to the main PCB, so all you need to do is build a small circuit that contains the spectrum analyzer which connects to the I/O pins on the cube PCB and also has audio input and output connections. First, consider the schematic:

MSGEQ7 CUBE4 spectrum analyser schematic

For the purposes of this project our spectrum analyser will only display the results from one channel of audio – if you want stereo, you’ll need two! And note that the strobe, reset and DCOUT pins on the MSGEQ7 are labelled with the connections to the cube PCB. Furthermore the pinouts for the MSGEQ7 don’t match the physical reality – here are the pinouts from the MSGEQ7 data sheet (.pdf):

MSGEQ7 pinouts

The circuit itself will be quite small and fit on a small amount of stripboard or veroboard. There is plenty of room underneath the cube to fit the circuit if so desired:

MSGEQ7 LED cube

With a few moments you should be able to trace out your circuit to match the board type you have, remember to double-check before soldering. You will also need to connect the audio in point after the 1000 pF capacitor to a source of audio, and also pass it through so you can connect powered speakers, headphones, etc.

One method of doing so would be to cut up a male-female audio extension lead, and connect the shield to the GND of the circuit, and the signal line to the audio input on the circuit. Or if you have the parts handy and some shielded cable, just make your own input and output leads:

MSGEQ7 input output leads

Be sure to test for shorts between the signal and shield before soldering to the circuit board. When finished, you should have something neat that you can hide under the cube or elsewhere:

MSGEQ7 RGB cube LED spectrum analyzer board

Double-check your soldering for shorts and your board plan, then fit to the cube along with the audio source and speakers (etc).

Arduino Sketch

The sketch has two main functions – the first is to capture the levels from the MSGEQ7 and put the values for each frequency band into an array, and the second function is to turn on LEDs that represent the level for each band. If you’ve been paying attention you may be wondering how we can represent seven frequency bands with a 4x4x4 LED cube. Simple – by rotating the cube 45 degrees you can see seven vertical columns of LEDs:

MSGEQ7 LED cube spectrum analyzer columns

So when looking from the angle as shown above, you have seven vertical columns, each with four levels of LEDs. Thus the strength of each frequency can be broken down into four levels, and then the appropriate LEDs turned on.

After this is done for each band, all the LEDs are turned off and the process repeats. For the sake of simplicity I’ve used the cube’s Arduino library to activate the LEDs, which also makes the sketch easier to fathom. The first example sketch only uses one colour:

… and a quick video demonstration:

For a second example, we’ve used various colours:

… and the second video demonstration:

A little bit of noise comes through into the spectrum analyser, most likely due to the fact that the entire thing is unshielded. The previous prototype used the Arduino shield from the tutorial which didn’t have this problem, so if you’re keen perhaps make your own custom PCB for this project.

visit tronixlabs.com

Have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column, or join our forum – dedicated to the projects and related items on this website.

Posted in analyzer, arduino, com-10468, cube, freetronics, LED, MSGEQ7, projects, rgb, RGB LED, spectrum, tronixlabs, tronixstuff, tutorial

Tutorial – twitter and the Arduino Yún

Introduction

After spending almost $100 on an Arduino Yún to see what the fuss was about, it seemed like a good idea to find and demonstrate some uses for it. So in this article we’ll examine how your Yún can send a tweet using some simple example sketches – and the first of several Arduino Yún-specific tutorials.

Getting Started

If you haven’t already done so, ensure your Arduino Yún can connect to your network via WiFi or cable – and get a Temboo account (we run through this here). And you need (at the time of writing) IDE version 1.5.4 which can be downloaded from the Arduino website. Finally, if you don’t have a twitter account – go get one.

Arduino Yun Yún front

Sending a tweet from your Yún

Thanks to Arduino and Temboo, 99% of the work is already done for you. To send a tweet requires the Arduino sketch, a header file with your Temboo account details, and also the need to register an application in the twitter development console.

Don’t panic, just follow the “Get Set Up” instructions from the following page. When you do – make sure you’re logged into the Temboo website, as it will then populate the header file with your Temboo details for you. During the twitter application stage, don’t forget to save your OAuth settings which will appear in the “OAuth Tool” tab in the twitter developer page, for example:

Arduino Yun OAuth twitter

… as they are copied into every sketch starting from the line:

When you save the sketch, make sure you place the header file with the name TembooAccount.h in the same folder as your sketch. You know this has been successful when opening the sketch, as you will see the header file in a second tab, for example:

Arduino Yun sketch header file

Finally, if you’re sharing code with others, remove your OAuth and TembooAccount.h details otherwise they can send tweets on your behalf.

OK – enough warnings. If you’ve successfully created your Temboo account, got your twitter OAuth details, fed them all into the sketch and header file, then saved (!) and uploaded your sketch to the Arduino Yún – a short tweet will appear on your timeline, for example:

Arduino Yun twiiter

If nothing appears on your twitter feed, open the serial monitor in the IDE and see what messages appear. It will feed back to you the error message from twitter, which generally indicates the problem.

Moving on, let’s examine how to send tweets with your own information. In the following example sketch we send the value resulting from analogRead(0) and text combined together in one line. Don’t forget twitter messages (tweets) have a maximum length of 140 characters. We’ve moved all the tweet-sending into one function tweet(), which you can then call from your sketch when required – upon an event and so on. The text and data to send is combined into a String in line 26:

Which results with the following example tweet:

Arduino Yun sends twitter data

With the previous example sketch you can build your own functionality around the tweet() function to send data when required. Recall that the data to send as a tweet is combined into a String at line 26.

Please note that you can’t blast out tweets like a machine, for two reasons – one, twitter doesn’t like rapid automated tweeting – and two, you only get 1000 free calls on your Temboo account per month. If you need more, the account needs to be upgraded at a cost.

Conclusion

Well the Yún gives us another way to send data out via twitter. It wasn’t the cheapest way of doing so, however it was quite simple. And thus the trade-off with the Arduino platform – simplicity vs. price. If there is demand, we’ll examine more connected functions with the Yún.

And if you’re interested in learning more about Arduino, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a third printing!) “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in arduino, tronixstuff, tutorial, twitter, Yún1 Comment

Review – “Ardublock” graphical programming for Arduino

Introduction

After helping many people get started with the world of Arduino and electronics,  we still find a small percentage of people who are turned off by the concept of programming or have trouble breaking larger tasks into smaller ones with regards to writing algorithms for their code/sketch.

So after being introduced to a new graphical programming tool called “Ardublock“, we were excited about the possibilities wanted to share it with our readers. Ardublock provides a truly graphical and non-coding solution to controlling an Arduino, that is an open-source product and thus free to download and try for yourself.

Installation

Ardublock is a Java application that runs from inside the Arduino IDE, which can be downloaded from here. It’s only one file, that needs to be placed in a new folder in the Arduino IDE. The folder names must be the same as shown below:

ardublock installation folder

Once you’ve copied the file, simply open the Arduino IDE and select Ardublock from the Tools menu:

arduino ide tools menu ardublockFrom which point a new window appears – the Ardublock “development environment”:

ardublock development environment

 Using Ardublock

It’s quite simple – you simply select the required function from the menu on the left and drag it into the large area on the right. For a quick example where we blink the onboard LED on and off – watch the following video:

 

The following image is the screen capture of the program from the video:

ardublock LED Blink

As you can see the “blocks” just fit together, and parameters can be changed with the right mouse button. After a few moments experimenting with the Ardublock software you will have the hang of it in no time at all.

And thus you can demonstrate it to other people and show them how easy it is. And there is much more than just digital output controls, all the functions you’re used to including I2C, variables, constants, servos, tone and more are available.

The only technical thing you need to demonstrate is that the Arduino IDE needs to stay open in the background – as once you have finished creating your program, Ardublock creates the required real Arduino sketch back in the IDE and uploads it to the board.

This is also a neat function – the user can then compare their Ardublock program against the actual sketch, and hopefully after a short duration the user will have the confidence to move on with normal coding.

Conclusion

Ardublock provides a very simple method of controlling an Arduino, and makes a great starting point for teaching the coding-averse, very young people or the cognitively-challenged. It’s open source, integrates well with the official IDE and works as described – so give it a go.

And if you enjoyed this review, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a third printing!) “Arduino Workshop” from No Starch Press.

tronixstuff

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in ardublock, arduino, software, software review, tronixstuff, tutorial3 Comments

Tutorial – Arduino and the TLC5940 PWM LED Driver IC

Use the Texas Instruments TLC5940 16-Channel LED Driver IC with Arduino in Chapter 57 of our Arduino Tutorials. The first chapter is here, the complete series is detailed here.

Introduction

Today we are going to examine the Texas Instruments TLC5940 16-channel LED driver IC. Our reason for doing this is to demonstrate another, easier way of driving many LEDs – and also servos.  First up, here is a few examples of the TLC5940

TLC5940

The TLC5940 is available in the DIP version above, and also surface-mount. It really is a convenient part, allowing you to adjust the brightness of sixteen individual LEDs via PWM (pulse-width modulation) – and you can also daisy-chain more than one TLC5940 to control even more.

During this tutorial we’ll explain how to control one or more TLC5940 ICs with LEDs and also look at controlling servos. At this point, please download a copy of the TLC5940_data_sheet (.pdf) as you will refer to it through this process. Furthermore, please download and install the TLC5940 Arduino library by Alex Leone which can be found here. If you’re not sure how to install a library, click here.

Build a TLC5940 demonstration circuit

The following circuit is the minimum required to control sixteen LEDs from your Arduino or compatible. You can use it to experiment with various functions and get an idea of what is possible. You will need:

  • An Arduino Uno or compatible board
  • 16 normal, everyday LEDs that can have a forward current of up to 20 mA
  • a 2 kΩ resistor (give or take 10%)
  • a 0.1uF ceramic and a 4.7uF electrolytic capacitor

Take note of the LED orientation – and remember the TLC5940 is a common-anode LED driver – so all the LED anodes are connected together and then to 5V:

TLC5940 Arduino circuit

For this particular circuit, you won’t need an external 5V power supply – however you may need one in the future. The purpose of the resistor is to control the amount of current that can flow through the LEDs. The required resistor value is calculated with the following formula:

R = 39.06 / Imax

where R (in Ohms)  is the resistor value and Imax (in Amps) is the maximum amount of current you want to flow through the LEDs. For example, if you have LEDs with a 20 mA forward current – the resistor calculation would be:

R = 39.06 / 0.02 = 1803 Ohms.

Once you have the circuit assembled – open up the Arduino IDE and upload the sketch BasicUse.pde  which is in the example folder for the TLC5940 library. You should be presented with output similar to what is shown in the following video:

Controlling the TLC5940

Now that the circuit works, how do we control the TLC5940? First, the mandatory functions – include the library at the start of the sketch with:

and then initialise the library by placing the following into void setup():

x is an optional parameter – if you want to set all the channels to a certain brightness as soon as the sketch starts, you can insert a value between 0 and 4095 for in the Tlc.init() function.

Now to turn a channel/LED on or off. Each channel is numbered from 0 to 15, and each channel’s brightness can be adjusted between 0 and 4095.

This is a two-part process…

First – use one or more of the following functions to set up the required channels and respective brightness (PWM level):

For example, if you wanted to have the first three channels on at full brightness, use:

The second part is to use the following to update the TLC5940 with the required instructions from part one:

If you want to turn off all channels at once, simply use:

You don’t need to call a TLC.update() after the clear function. The following is a quick example sketch that sets the brightness/PWM values of all the channels to different levels:

and the sketch in action:

The ability to control individual brightness for each channel/LED can also be useful when controlling RGB LEDs – you can then easily select required colours via different brightness levels for each element.

Using two or more TLC5940s

You can daisy-chain quite a few TLC5940s together to control more LEDs. First – wire up the next TLC5940 to the Arduino as shown in the demonstration circuit – except connect the SOUT pin (17) of the first TLC5940 to the SIN pin (26) of the second TLC5940 – as the data travels from the Arduino, through the first TLC5940 to the second and so on. Then repeat the process if you have a third, etc. Don’t forget the resisotr that sets the current!

Next, open the file tlc_config.h located in the TLC5940 library folder. Change the value of NUM_TLCS to the number of TLC5940s you have connected together, then save the file and also delete the file Tlc5940.o also located in the same folder. Finally restart the IDE. You can then refer to the channels of the second and further TLC5940 sequentially from the first. That is, the first is 0~15, the second is 16~29, and so on.

Controlling servos with the TLC5940

As the TLC5940 generates PWM (pulse-width modulation) output, it’s great for driving servos as well. Just like LEDs – you can control up to sixteen at once. Ideal for creating spider-like robots, strange clocks or making some noise. When choosing your servo, ensure that it doesn’t draw more than 120 mA when operating (the maximum current per channel) and also heed the “Managing current and heat” section at the end of this tutorial. And use external power with servos, don’t rely on the Arduino’s 5V line.

To connect a servo is simple – the GND line connects to GND, the 5V (or supply voltage lead) connects to your 5v (or other suitable supply) and the servo control pin connects to one of the TLC5940’s outputs. Finally – and this is important – connect a 2.2kΩ resistor between the TLC5940 output pin(s) being used and 5V.

Controlling a servo isn’t that different to an LED. You need the first two lines at the start of the sketch:

then the following in void setup():

Next, use the following function to select which servo (channel) to operate and the required angle (angle):

Just like the LEDs you can bunch a few of these together, and then execute the command with:

So let’s see all that in action. The following example sketch sweeps four servos across 90 degrees:

And the following video captures those four servos in action:

 

If you servos are not rotating to the correct angle – for example you ask for 180 degrees and they only rotate to 90 or thereabouts, a little extra work is required. You need to open the tlc_servos.h file located in the TLC5940 Arduino library folder and experiment with the values for SERVO_MIN_WIDTH and SERVO_MAX_WIDTH. For example change SERVO_MIN_WIDTH from 200 to 203 and SERVO_MAX_WIDTH from 400 to 560.

Managing current and heat 

As mentioned earlier, the TLC5940 can handle a maximum of 120 mA per channel. After some experimenting you may notice that the TLC5940 does get warm – and that’s ok. However there is a maximum limit to the amount of power that can be dissipated before destroying the part. If you are just using normal garden-variety LEDs or smaller servos, power won’t be a problem. However if you’re planning on using the TLC5940 to the max – please review the notes provided by the library authors.

Conclusion

Once again you’re on your way to controlling an incredibly useful part with your Arduino. Now with some imagination you can create all sorts of visual displays or have fun with many servos. And if you enjoyed the tutorial, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a third printing!) “Arduino Workshop” from No Starch Press.

tronixstuff

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in arduino, BOB-10616, COM-10136, LED, PWM, servo, TI, tlc5940, tronixstuff, tutorial15 Comments

Tutorial – Arduino and the MAX7219 LED Display Driver IC

Use the Maxim MAX7219 LED display driver with Arduino in Chapter 56 of our Arduino Tutorials. The first chapter is here, the complete series is detailed here.

Introduction

Sooner or later Arduino enthusiasts and beginners alike will come across the MAX7219 IC. And for good reason, it’s a simple and somewhat inexpensive method of controlling 64 LEDs in either matrix or numeric display form. Furthermore they can be chained together to control two or more units for even more LEDs. Overall – they’re a lot of fun and can also be quite useful, so let’s get started.

Here’s an example of a MAX7219 and another IC which is a functional equivalent, the AS1107 from Austria Microsystems. You might not see the AS1107 around much, but it can be cheaper – so don’t be afraid to use that instead:

MAX7219 AS1107

 At first glance you may think that it takes a lot of real estate, but it saves some as well. As mentioned earlier, the MAX7219 can completely control 64 individual LEDs – including maintaining equal brightness, and allowing you to adjust the brightness of the LEDs either with hardware or software (or both). It can refresh the LEDs at around 800 Hz, so no more flickering, uneven LED displays.

You can even switch the display off for power saving mode, and still send it data while it is off. And another good thing – when powered up, it keeps the LEDs off, so no wacky displays for the first seconds of operation. For more technical information, here is the data sheet: MAX7219.pdf. Now to put it to work for us – we’ll demonstrate using one or more 8 x 8 LED matrix displays, as well as 8 digits of 7-segment LED numbers.

Before continuing, download and install the LedControl Arduino library as it is essential for using the MAX7219.

Controlling LED matrix displays with the MAX7219

First of all, let’s examine the hardware side of things. Here is the pinout diagram for the MAX7219:

MAX7219 pinout

The MAX7219 drives eight LEDs at a time, and by rapidly switching banks of eight your eyes don’t see the changes. Wiring up a matrix is very simple – if you have a common matrix with the following schematic:

LED matrix pinoutsconnect the MAX7219 pins labelled DP, A~F to the row pins respectively, and the MAX7219 pins labelled DIG0~7 to the column pins respectively. A total example circuit with the above matrix  is as follows:

MAX7219 example LED matrix circuit

The circuit is quite straight forward, except we have a resistor between 5V and MAX7219 pin 18. The MAX7219 is a constant-current LED driver, and the value of the resistor is used to set the current flow to the LEDs. Have a look at table eleven on page eleven of the data sheet:

MAX7219 resistor tableYou’ll need to know the voltage and forward current for your LED matrix or numeric display, then match the value on the table. E.g. if you have a 2V 20 mA LED, your resistor value will be 28kΩ (the values are in kΩ). Finally, the MAX7219 serial in, load and clock pins will go to Arduino digital pins which are specified in the sketch. We’ll get to that in the moment, but before that let’s return to the matrix modules.

In the last few months there has been a proliferation of inexpensive kits that contain a MAX7219 or equivalent, and an LED matrix. These are great for experimenting with and can save you a lot of work – some examples of which are shown below:

MAX7219 LED matrix modules

At the top is an example from tronixlabs.com, and the pair on the bottom are the units from a recent kit review. We’ll use these for our demonstrations as well.

Now for the sketch. You need the following two lines at the beginning of the sketch:

The first pulls in the library, and the second line sets up an instance to control. The four parameters are as follows:

  1. the digital pin connected to pin 1 of the MAX7219 (“data in”)
  2. the digital pin connected to pin 13 of the MAX7219 (“CLK or clock”)
  3. the digital pin connected to pin 12 of the MAX7219 (“LOAD”)
  4. The number of MAX7219s connected.

If you have more than one MAX7219, connect the DOUT (“data out”) pin of the first MAX7219 to pin 1 of the second, and so on. However the CLK and LOAD pins are all connected in parallel and then back to the Arduino.

Next, two more vital functions that you’d normally put in void setup():

The first line above turns the LEDs connected to the MAX7219 on. If you set TRUE, you can send data to the MAX7219 but the LEDs will stay off. The second line adjusts the brightness of the LEDs in sixteen stages. For both of those functions (and all others from the LedControl) the first parameter is the number of the MAX7219 connected. If you have one, the parameter is zero… for two MAX7219s, it’s 1 and so on.

Finally, to turn an individual LED in the matrix on or off, use:

which turns on an LED positioned at col, row connected to MAX7219 #1. Change TRUE to FALSE to turn it off. These functions are demonstrated in the following sketch:

And a quick video of the results:

How about controlling two MAX7219s? Or more? The hardware modifications are easy – connect the serial data out pin from your first MAX7219 to the data in pin on the second (and so on), and the LOAD and CLOCK pins from the first MAX7219 connect to the second (and so on). You will of course still need the 5V, GND, resistor, capacitors etc. for the second and subsequent MAX7219.

You will also need to make a few changes in your sketch. The first is to tell it how many MAX7219s you’re using in the following line:

by replacing X with the quantity. Then whenever you’re using  a MAX7219 function, replace the (previously used) zero with the number of the MAX7219 you wish to address. They are numbered from zero upwards, with the MAX7219 directly connected to the Arduino as unit zero, then one etc. To demonstrate this, we replicate the previous example but with two MAX7219s:

And again, a quick demonstration:

Another fun use of the MAX7219 and LED matrices is to display scrolling text. For the case of simplicity we’ll use the LedControl library and the two LED matrix modules from the previous examples.

First our example sketch – it is quite long however most of this is due to defining the characters for each letter of the alphabet and so on. We’ll explain it at the other end!

The pertinent parts are at the top of the sketch – the following line sets the number of MAX7219s in the hardware:

The following can be adjusted to change the speed of text scrolling:

… then place the text to scroll in the following (for example):

Finally – to scroll the text on demand, use the following:

You can then incorporate the code into your own sketches. And a video of the example sketch in action:

Although we used the LedControl library, there are many others out there for scrolling text. One interesting example is Parola  – which is incredibly customisable.

Controlling LED numeric displays with the MAX7219

Using the MAX7219 and the LedControl library you can also drive numeric LED displays – up to eight digits from the one MAX7219. This gives you the ability to make various numeric displays that are clear to read and easy to control. When shopping around for numeric LED displays, make sure you have the common-cathode type.

Connecting numeric displays is quite simple, consider the following schematic which should appear familiar by now:

MAX7219 7-segment schematic

The schematic shows the connections for modules or groups of up to eight digits. Each digit’s A~F and dp (decimal point) anodes connect together to the MAX7219, and each digit’s cathode connects in order as well. The MAX7219 will display each digit in turn by using one cathode at a time. Of course if you want more than eight digits, connect another MAX7219 just as we did with the LED matrices previously.

The required code in the sketch is identical to the LED matrix code, however to display individual digits we use:

where A is the MAX7219 we’re using, B is the digit to use (from a possible 0 to 7), C is the digit to display (0~9… if you use 10~15 it will display A~F respectively) and D is false/true (digit on or off). You can also send basic characters such as a dash “-” with the following:

Now let’s put together an example of eight digits:

and the sketch in action:

Conclusion

We have only scratched the surface of what is possible with the MAX7219 and compatible parts. They’re loads of fun and quite useful as well. And finally a plug for our own store – tronixlabs.com – which along with being Australia’s #1 Adafruit distributor, also offers a growing range and Australia’s best value for supported hobbyist electronics from DFRobot, Freetronics, Seeedstudio and much much more.

visit tronixlabs.com

Posted in arduino, as1107, COM-09622, LED matrix, lesson, max7219, part review, tronixlabs, tronixstuff, tutorial

Review – Freetronics 128×128 Pixel Colour OLED Module

Introduction

Time for another review, and in this instalment we have the new 128×128 Pixel OLED Module from Freetronics. It’s been a while since we’ve had a full-colour graphic display to experiment with, and this one doesn’t disappoint. Unlike other displays such as LCD, this one uses OLED – “Organic Light-Emitting Diode” technology.

OLEDs allow for a faster refresh rate, and to the naked eye has a great amount of colour contrast. Furthermore the viewing angles are excellent, you can clearly read the display from almost any angle, for example:

freetronics OLED display bottom view

freetronics OLED display side

However they can suffer from burn-in from extended display of the same thing so that does need to be taken into account. Nevertheless they provide an inexpensive and easy-to-use method of displaying colour text, graphics and even video from a variety of development boards. Finally – there is also a microSD socket for data logging, image storage or other uses. However back to the review unit. It arrives in typical retail packaging:

freetronics OLED display

and includes the OLED display itself, a nifty reusable parts tray/storage box, and two buttons. The display has a resolution of 128 x 128 pixels and has a square display area with a diagonal size of 38.1 mm. The unit itself is quite compact:

freetronics OLED display front

freetronics_OLED_display_rear

The display is easily mounted using the holes on the left and right-hand side of the display. The designers have also allowed space for an LED, current-limiting resistor and button on each side, for user input or gaming – perfect for the  included buttons. However this section of the PCB is also scored-off so you can remove them if required. Using the OLED isn’t difficult, and tutorials have been provided for both Arduino and Raspberry Pi users.

Using with Arduino

After installing the Arduino library, it’s a simple matter of running some jumper wires from the Arduino or compatible board to the display – explained in detail with the “Quickstart” guide. Normally I would would explain how to use the display myself, however in this instance a full guide has been published which explains how to display text of various colours, graphics, displaying images stored on a microSD card and more. Finally there’s some interesting demonstration sketches included with the library. For example, displaying large amounts of text:

… the variety of fonts available:

freetronics OLED font demonstration

… and for those interested in monitoring changing data types, a very neat ECG-style of sketch:

… and the mandatory rotating cube from a Freetronics forum member:

Using with Raspberry Pi

For users of this popular single-board computer, there’s a great tutorial and some example videos available on the Freetronics website for your consideration, such as the following video clip playback:

Support

Along with the Arduino and Raspberry Pi tutorials, there’s also the Freetronics support forum where members have been experimenting with accelerated drivers, demonstrations and more.

Competition!

For a chance to win your own OLED display, send a postcard with your email address clearly printed on the back to:

OLED Competition, PO Box 5435 Clayton 3168 Australia. 

Cards must be received by 24/10/2013. One card will then be selected at random and the winner will be sent one Freetronics OLED Display. Prize will be delivered by Australia Post standard air mail. We’re not responsible for customs or import duties, VAT, GST, import duty, postage delays, non-delivery or whatever walls your country puts up against receiving inbound mail.

Conclusion

Compared to previous colour LCD units used in the past, OLED technology is a great improvement – and demonstrated very well with this unit. Furthermore you get the whole package – anyone call sell you a display, however Freetronics also have the support, tutorials, drivers and backup missing from other retailers. So if you need a colour display, check it out.

And for more detail, full-sized images from this article can be found on flickr. And if you’re interested in learning more about Arduino, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a third printing!) “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

[Note – OLED display was a promotional consideration from Freetronics]

Posted in arduino, freetronics, LCD, OLED, product review, raspberry pi, review, tutorial0 Comments

Kit Review – Maniacal Labs Epoch Clock

Introduction

The subject of our latest kit review is the “Epoch Clock” from Maniacal Labs, a new organisation started by three young lads with some interesting ideas. Regular readers will know we love a clock – so when the opportunity came to review this one, we couldn’t say no.

At this point you may be thinking “what is Epoch time anyway?”. Good question! It is the number of seconds elapsed since the first of January, 1970 (UTC) – and used by Unix-based computers as the start of their time universe. (For more on the theory of Epoch time, check out Wikipedia). For example – 1379226077 Epoch time is Sun, 15 Sep 2013 06:21:17 GMT. That’s a lot of seconds. If you’re curious, you can do more calculations with the EpochTime website.

Moving forward, this clock kit will show Epoch time in full 32-bit binary glory, using a DS1307 real-time clock IC (with backup battery) and is controlled with an ATmega328P-PU – so you can modify the code easily with the Arduino IDE or WinAVR (etc).

Assembly

The creators have spent a lot of time on not only the packaging and out-of-box-experience, but also the documentation and setup guide – so as long as you’re fine with simple through-hole soldering the kit will not present any challenges. The kit arrives in a sturdy box:

binary epoch clock kit box

… with well packaged components. Everything is included for the finished product, as well as IC sockets, the RTC backup battery and a USB cable so you can power the clock from a USB hub:

binary epoch clock kit box contents

binary epoch clock kit parts contents

The PCB is a good thickness, and has a clear silk-screen and solder mask:

binary epoch clock kit PCB

binary epoch clock kit PCB bottom

Construction is simple, just follow the step-by-step instructions. Starting with the USB socket for power:

binary epoch clock kit USB socket

binary epoch clock kit USB socket bottom

… then the resistors:

binary epoch clock kit resistors

… the LEDs:

binary epoch clock kit first LEDs

… all 32 of them. Note that the LEDs don’t sit flush with the PCB, so a little effort is required to keep them aligned:

binary epoch clock kit all LEDs

 Then the rest of the components just fit as expected. I’ve also added the included header pins for an FTDI programming cable and ICSP to keep my options open:

binary epoch clock kit almost finished

Then simply fit the battery, insert the ICs and you’re done:

binary epoch clock kit finished

Using the clock

The microcontroller is pre-programmed, so you can use the clock straight away. You will however need to set the time first. To make this incredibly easy, there is a special web page that displays the current time and Epoch time, which steps you through the process of setting the time using the buttons.

Or with some code available on the kit github page and a programming cable, you can automatically sync it to the clock. Once setup, the battery will keep the current time in the RTC nicely. The clock is powered by 5V, which is easily supplied with the included USB cable, or you can always hack in your own feed.

So what does Epoch time in 32-bit binary look like? Here’s a short video of the clock in action:

Reading the time requires converting the binary number displayed with the LEDs back to a decimal number – which is of course the Epoch count of seconds since 1/1/1970. Math teachers will love this thing.

But wait, there’s more!

If you get tired of the blinking, there’s a test function which is enabled by holding down both buttons for a second, which turns the Epoch Clock into a nifty Larson Scanner:

To create your own sketches or examine the design files in more detail, it’s all on the clock github page. From a hardware perspective you have an ATmega328P-PU development board with a DS1307 battery-backed real-time clock – with 32 LEDs. So you could also create your own kind of clock or other multi-LED blinking project without too much effort. Review the EpochClockSchematic (.pdf) to examine this in more detail.

Conclusion

I really enjoyed this kit – it was easy to assemble, I learned something new and frankly the blinking LEDs can be quite soothing. The clock would make a great for a conversation-starter in the office, or would make an ideal gift for any Sheldon Cooper-types you might be associated with. Or have competitions to see who can convert the display to normal time. After shots.

Nevertheless it’s a fun and imaginative piece of kit, fully Open Hardware-compliant – and if you’ve made it this far – get some and have fun. Full-sized images are on flickr. Interested in Arduino? Check out my new book “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

[Note – The kit reviewed was a promotional consideration from Maniacal Labs]

Posted in arduino, ds1307, epoch time, kit review, linux, real time clock, tronixstuff1 Comment

Initial Review – Goldilocks Arduino-compatible with ATmega1284P

Introduction

In March this year we discussed a project by Phillip Stevens to crowd-fund an Arduino-compatible board with an ATmega1284p microcontroller – the “Goldilocks”. After being funded at a rapid rate, and subjected to some community feedback – the boards have now been manufactured and delivered to those who pledged. If you missed out – there’s some more available for direct sales. We ordered five and now have them for the subject of this review – and two to give away. So let’s examine the board and see what’s new.

What is it?

After hitting the limits of the Arduino Uno with respect to SRAM, CPU speed and not wanting to lose compatibility with existing projects by changing platforms, Philip decided to shift the MCU up to the ATmega1284P. This offers eight times the SRAM, four times the flash memory and EEPROM – and is also clocked at 20 MHz instead of the usual 16 MHz on Unos, etc. After the original design was announced, it was the victim of some pretty heavy feature-creep – however with Freetronics as the manufacturing partner the final result is a nicely-finished product:

freetronics goldilocks

Now let’s rip open the packaging and examine the board in greater detail. From the images below you can get the gist of things… starting with the top you can see the ATmega1284P next to the microSD card socket. There’s a JTAG connector for the 1284P on its left – and below that a 32.768 kHz crystal for RTC use. And like other Freetronics boards a large prototyping area has been squeezed in below pins D0~7 that also has the power and I2C lines at the edge. Furthermore note that all I/O pins are brought out to separate holes in alignment with the header sockets. And my favourite – a switch-mode power supply circuit that can offer up to 2A of current – great for GSM shields.

freetronics goldilocks top

Another point of interest is the ATmega32U2 microcontroller which is for USB duties – however it can be used as a separate “board” on its own, with a separate reset button, ICSP breakout and the ports are broken out logically:

freetronics goldilocks atmega32u2

Furthermore the 32U2’s SPI bus can be wired over to the main 1284P to allow communication between the two – simply by bridging the provided pads on the PCB you can join them. Also on the bottom you can see how each I/O pin can be disconnected from the I/O areas and thus diverted if necessary. It really is a testament to the design that so much of the board is customisable, and this attention to detail makes it stand apart from the usual Arduino-compatibles out there.

freetronics goldilocks bottom

One thing that did strike me was the retina-burning intensity of the onboard LEDs – however you can disable them by cutting the provided track on the PCB. For a complete explanation of the hardware side of things, check out the user guide.

Using the Goldilocks

One of the main goals was to be Arduino Uno R3-compatible, and from initial examination this is certainly the case. However there are a couple of differences, which you can find out more about in the user guide. This is not the first board for an Arduino user, but something chosen after getting some experience. Installation was very easy, it should be plug-and-play for the non-Windows crowd. However if you’re part of the silent majority of Windows users then the required U2duino Programmer.inf file for the Device Manager will be found in the production_firmware folder of the software download available on the product page. Furthermore no matter your OS – don’t forget to install the Arduino IDE Goldilocks board profile.

Before getting too excited and uploading your sketches, you can examine the the ATmega1284p bootloader monitor which allows for memory dumps, port testing, and more. Simply connect up your board, load the Arduino IDE, select the board and COM: port then open the Serial Monitor. By sending “!!!” after a board reset, a simple menu appears – which is shown in the following video:

Now for a quick speed test. We’ll use a sketch written by Steve Curd from the Arduino forum. It calculates Newton Approximation for pi using an infinite series: