Noe’s Juke Box | Main components and schematics

Main parts

Juke Box showed here is based on the following main components :

components photo

  • an Arduino Mega (here a clone from DF Robot) as the “brain”
  • an Adafruit Music Maker for music & midi player
  • a Sparkfun’s button par and associated PCB (need to get leds separately)
  • some simple illuminated push buttons from found at Adafruit
  • a rotary encoder. Strangely enough, the RGB one I found at Sparkfun is the only which has a threaded shaft with a bolt and then can be mounted on a chassis
  • and last but not least an accellerometer breakout board just for fun also from Sparkfun

Connecting the button pad

Connecting the Arduino to the button pad is not complex but there are quite a bit of wires between them… I already went through this here. But I changed the pins I used in the first place. Just that I thought it would simplify soldering later on by keeping related pins together as much as possible. Not sure it did simplify though…

final button pad connection

And PWM pins have been chosen precisely because you don’t want to use pins 4 and 13… More on this here.

And last, resistors for the leds are 150Ω, 100Ω and 100Ω for red, green and blue pins.

 Now, the Music Maker

The Adafruit’s Music Maker is based on the VS1053 chip which has 2 main functions : MP3/WAV/OGG… player and MIDI synth. It comes with a handy SD card connector from which it can read files to play. It comes in several flavors :

I chose the latter for two reasons : I liked the idea of having an onboard amp so it would simplifiy cabling and I thought I could stack it onto the Mega. But… as it is using by default PWM pins I desperately need for controlling the leds, I had to re-cable everything to new pins. In addition, I could not stack it anyway because I needed all the space on the Mega proto shield as you’ll see later on.

So, in the end, if I had to do it again, I would probably get the breakout board (smaller, much smaller) and the 3W amp separately.

Here are the connections

music maker connection

Schematic based on Adafruit’s Music Maker catalog product photo

Note the little voltage divider to feed GPIO 1 on the VS1052 : the VS is a 3.3V device so feeding directly with Arduino’s 5V may (will) damage it.

 Then the accellerometer

I choose a cheap 3-axis, I2C capable accellerometer breakout : the Sparkfun’s MMA8452 breakout board.

It has some nice features and can make use of 2 interrupts… but I only have one available… So the other one won’t be connected for now. My first version of arduino code won’t make use of any of it for now. So it does not matter. I did connect one… just in case I have an idea on how I could use it !


Schematic based on Sparkfun’s catalog product photo

Let’s continue with the encoder

The Sparkfun’s encoder is a bit tricky because documentation is not quite clear but in the end… it works !

encoder connection

Note that it is a common anode RGB led. Setting pins D12, D13 or D14 to 0 means ON and 255 means OFF !

And last, resistors for the leds are 150Ω, 100Ω and 100Ω for red, green and blue pins. Also, pull-down resistor for the switch is 10kΩ

Let’s finish with the buttons

And now the very last thing : the illuminated buttons.

button rear connection

Schematic based on Adafruit’s catalog product photo


Have 3 of them. Quite straight forward… just don’t forget 150Ω led resistors.

Wrap up

Ok… all parts have been connected one by one, here is the full picture !

schematic 1500

 And what about Arduino code

All is here on GitHub :

What’s next

In next posts, I will sho how I did assemble all that stuff and build a nice enclosure for it.

Sparkfun’s 4×4 Button & LED Matrix – Part 3 – Playing with the pad

In previous posts, we saw how to assemble the pad and how to connect it to an arduino MEGA and use a very simple program to switch led on and of using the keypad. Now, this is getting a bit more complex as we will :

  • detect simultaneous key press (up to 10)
  • use key status (PRESSED, HOLD, RELEASED and IDLE) to do stuff
  • lights up multiple leds with different colors

What the program will do

On startup, it will lights up every led in red, green, blue and white successively. It is just a test to verify that the 3 RGB pins of all leds are properly wired to the arduino.

Then, it will lights up all leds at once with random colors.

Then, when using a key :

  • If the led off
    • When key is pressed, led will be switched on with a random color
    • if the key is not held long enough, the led will be switched off when the key is released
    • if the key is held long enough, when it is released, led will stay on
  • If the led is on
    • When key is pressed, led color will change
    • if the key is not held long enough, the led will be switched off when the key is released
    • if the key is held long enough, when it is released, led will stay on with the new color

[youtube width=”640″ height=”360″][/youtube]

Not really usefull… but it should show how all this works and get you started the the pad !

Detecting multiple key press

No magic here : I simply used Keypad library from Arduino’s playground. I used the MultiKey example provided with the library to get my code working.

How to get all leds switched on with different colors

4×4 led matrix (more specifically Sparkfun’s 4×4 led matrix) requires :

  • 3 x 4 PMW pins that is 3 pins per row of 4 leds (against 3×16=48 PWM pins if each led was to be controlled individually)
  • 4 ground pins (against 16 pins…)

(See here for some details on RGB leds and have a look here for PWM pins.)

Let say PWM pins are rows and GND pins are columns

4x4 button pad sample with pins

If you want to make the B2 led red, then you just set D5 to 255 and D32 to LOW.

4x4 button pad sample 1 red

But, although requiring much less pins, matrix have some drawbacks :  what if you want to ligh up B2 and C3 and also B2 to be red and D2 to be green ? All at the same time ?

4x4 button pad sample 3 red green blue

All 4 leds in a row share the very same 3 “colors” pins and all leds in a column share the very same ground. It is not directly possible to have 2 differents colors for 2 leds on the same row. And it is not possible to switch on only 2 leds which are not on the same columns.

One way is to switch all leds on and off successively. Or better (more efficient),

  1. set colors on all the rows for the 1st column
  2. switch column on
  3. wait “leds on” for a little while (else leds will look quite dimmed)
  4. switch column off
  5. go to the next column (back to 1)

4x4 button pad sample 4 process

I noticed that waiting for 4ms was giving some fickering. I needed 3ms or less to get a “flicker free” display.  I finally get down to 300μs “led on” period. This is sufficient to get the maximum brightness and definitively get rid of flickering.

Here is a small video showing the same led pattern as above, starting with a 500ms period down to 2ms.

[youtube width=”640″ height=”360″][/youtube]

PWM trick

I did connect the leds a bit differently than in the previous article. That is, I swapped  pins
4 & 13 respectively with pin 44 & 45. Why didn’t I used pin 4 & 13 and 44 & 45 instead ?

Because I needed to increase PWM frequency to make the matrix works. To do this, you need to change timers config. Pins 4 and 13 use timer 0. But… as timer 0 is used by Arduino’s core timing functions, you don’t want to mess with it. Do you ?

But why the heck did I want to change PWM frequency ! Because it too “slow” by default. On an Arduino MEGA, default frequencies are :

  • 976.56 Hz for pin 4 & 13
  • 490.20 Hz for all other PWM pins

As stated above, I won’t be using pins 4 & 13. So frequency fo pins I use is a bit less that 500 Hz, that is, a period is a bit higher that 2ms. This is veeeeeeeery loooong… waaaaaay too long because I wait for 300μs and can only “wait” up for 3ms max anyway (not to get flickering). So, even for 3ms, that is around 1 and a half PWM period. This is not enough to get a stable color.

So I increased PWM frequency to the maximum, i.e. 31372.55 Hz. That makes a PWM period of ~32μs which is much smaller of even the smallest 300μs “led on” period.

More on PWM :


And now the code

I finally built up my very first library based on some OO code. It is to be used with an Arduino Mega and the Sparkfun’s 4×4 button pad.

As this is my first library, it may (does) require improvements… I know. But I hope it will at least get you started !

All the code is here on GitHub.

Sparkfun’s 4×4 Button & LED Matrix – Part 2 – Connecting to an Arduino Mega

I described, in a previous post, how to assemble a 4×4 Sparkun’s button and led matrix. Let see how to connect it.

Because of the (quite) large number of leds and button, I will be using an Arduino MEGA. That will allow to drive RGB leds and button without any additionnal  component. Well… almost : we’ll still need

  • 12 150Ω resistor for the RGB leds
  • a few jumper wires
  • 3 small breadboards
  • an Arduino MEGA of course

RGB led and Arduino

RGB LED detailsAn RGB led is actually… 3 leds : 1 Red, 1 Green and 1 Blue (thus RGB). They all share a common cathode and have 3 anodes, 1 per color.

Choosing the voltage applied to each color allows to choose the brightness of each color, allowing, in turn, to display a broad range of colors.

An Arduino does not have analog outputs. Only digital ones. So we’ll use digital output to “simulate”  analog ones using a technique called PWM. For more details on PWM see here.

Wiring the button & led matrix

Without the matrix, we would need 3×16=48 PWM pins… that’s a lot. With the matrix, we only have 4 rows, each row being connected to 4 leds. This implies some limitations but we now only need 3×4=12 PWM pins and Arduino MEGA 2560 has… 15 of it. Phew…

In addition of connecting the anodes to PWM pins, we also need to connect the cathodes to  simples digital pins. We only need 4 of them because we have 4 columns, each column being populated with 4 leds sharing the GND.

And then, we’ll need 4 digital pins for button GND (cols) and 4 more for signal (rows)

button pad connection

You’ll find an interresting article about about keyboard matrix here.

And put it in a box !

I used the box in which my netatmo thermostat was provided : a nice cube with the perfect size ! I’ve done a bit of cut in the box and the spacers and here is the final result :

In the box closedIn the box opened

 A simple test program

We’we wired evrything up, we can start programming the gizmo and see what it can do. You will find a test program here.


As you see, it is quite simple : at startup, it senquentially lights up all leds then, on each button press, it light up the corresponding led, changing color each time.

It is just for testing. I’ll work on some more interresting programs and post them !

Sparkfun’s 4×4 Button & LED Matrix – Part 1 – Soldering


There are quite a few project out there using Sparkfun’s Button Pad 4×4 – LED Compatible and associated Button Pad 4×4 – Breakout PCB. But most of the time there are either using monochrome leds and a shift register to drive the leds or just using a 2×2 matrix. So I decided to write my own build guide with RGB leds and an Arduino MEGA.

This is the first part of this building guide. In this part, I’ll list parts I used and show how I soldered everything together. In next part, I will describe connection of the pad to an Arduino MEGA and all necessary code to test it and make some fun things.

The parts

You’ll need :

That’ll be it for the soldering. But in the next parts, I will also be using

  • 1 Arduino Mega
  • 12 150Ω resistors
  • a few jumper wires
  • one big breadboard (or 3 small ones)

I bought my parts mainly from 2 french retaillers in or near Paris : Lextronic as they are a Sparkfun’s reseller and Saint-Quentin Radio for basic electronic pars (such as resistors, diodes, cable…) But you can find almost everything at Sparkfun’s or your prefered shop !

The soldering

Lets have a look at the PCB first. On the “bottom” side, we will solder the 1N4148 diodes and the BERG connectors. On the “top” side, where the botton pad will rest, we will solder the RGB leds.

4x4 Button Pad Breakout PCB Bottom

Bottom side : where diodes and connectors go

4x4 Button Pad Breakout PCB Top

Top side : where RGB leds and rubber buttons pad (below) goes4x4 Button pad

1N4148 diodes : the easy part

Not much to say really… Just bend the legs, insert the 16 diodes required in the proper holes and solder. Just one thing to take care of : the orientation on the diode !


Then, solder the diodes on the top side, taking care of not putting to much solder as you will need to trim the legs as close as possible from the PCB (I used a specific plier / cutter like this one) so it won’t get in the way of the rubber buttons pad.

RGB leds

Not much more complex. But leds I used have legs a bit closer from one another that the holes are. So you need to bend the legs before trying to insert them. If you don’t, you won’t be able to push them enough.


Then solder the legs of the leds !

The BERG connectors

Again, one tricky part is that you need to keep soldering on the top side as “flat” as possible, else, rubber pad won’t lay down properly on the PCB.

What I did is “trim” the BERG connector BEFORE soldering so it flush with the PCB. Doing it after is much more difficult and you may (will) damage the solder joint.  Whan soldering, make sure you heat the BERG pins with the iron so that you build a solid solder joint.

        BERG trimmed

BERG soldered flat


Ok, now we need some wires to connect the PCB to an arduino. I used a 4 wire ribbon cable. On one side, I just tin-plated the wires so that they can be easily used with a solderless breadboard. On the other side, I used the female BERG connectors.

berg femake berg female and cap berg female and wire

Connecteur BERG et Cable

 And in the end…

… we get a fully assembled button pad !

button pad assembled connector sidebutton pad assembled led side


Building a sound based toy

I have been a bit busy lately at work so I did not work a lot on my different projects. But after a discussion with my sister who was complaining about  the fact that there was no “good” music based toy for her 18 months old child, I was wondering what I could do about it.

Wandering around, I discovered a few things like a “wall Piano” based on a PICAXE-08M2 microcontroller and an ultrasonic Range Finder (see here). But nothing really nice and fun for a very young child. I finally discovered a very very nice project : monome. Ok… a bit complex for a child and surely to expensive ! Looking for some monome clone, I finally stumbled upon Sugarcube Midi Controller. Small enough, nice illuminated buttons, some fun features using accellerometers…

But… it is a midi controller, meaning that it does not play music by itself but controls a midi player like a PC. So I need to make it more autonomous. So my next project is there : build an easy to use & fun sound box, based on Amanda Ghassaei‘s Sugarcube project with specific features like RGB leds, embedded MP3 player and MIDI player, and make it fun for a child !

Still thinking about it…