Cozy Coupe Retrofit

Hot Dog!



The Little Tike Cozy Coupe, a children’s classic made of soft hollow plastic (LPDE), is a blank canvas for tinkering and customization.  While the car comes with some entertainment options, such a squeaker in the horn, I think that my client deserves something a little more realistic and, of course, high-tech.

This wasn’t a particularly difficult project, but it did take a bit of time to set up.  The overall concept is to create a media controller which plays different sounds depending on the button pressed.  I figured I could replace the toy key with a giant button and also fill the blank space on the left with some buttons to select the music.  I found a large arcade button and four smaller pushbuttons from Adafruit that would fit perfectly.


Microcontroller & Music

The music player is an Arduino Uno and Wave Shield.  The shield is an affordable addition to the Arduino Uno microcontroller that allows it to play uncompressed audio files of any length.  It’s very convenient for the purposes of this project since it reads WAV files off of a standard SD card and outputs it all to a 3.5mm jack.  It also leaves enough input ports for the buttons to be attached later on.

As luck would have it, I had both a speaker and stereo jack on hand, so it’s time to fire up the soldering iron to prep make the speaker rig.



Setting up the buttons was fairly straightforward: strip the ends, tin the wires and route the cables to the right position.  I felt like I was working on a real car having to pull cable and neatly tuck everything out of sight.



You’ll notice that I did quite a bit of cutting into the car body for this project and I certainly didn’t want to leave any wires or electronics exposed for prying fingers.  The 3D printer got some exercise and I made a replacement cover and looks just like a car hood.



Power comes by way of a USB charging pack that, you guessed it, I had lying around.  The Arduino can be powered through the USB connection and this pack provides plenty of juice for hours of usage.  Plus, it’s red and matches the car nicely.



Here are some shots of the setup.  I’m very happy with the look and fitment of all of the buttons.  The LEDs are nice and bright, even against the very bold plastic.




Client Assessment

I think we have a happy client!


#include <FatReader.h>
#include <SdReader.h>
#include <avr/pgmspace.h>
#include "WaveUtil.h"
#include "WaveHC.h"

SdReader card; // This object holds the information for the card
FatVolume vol; // This holds the information for the partition on the card
FatReader root; // This holds the information for the filesystem on the card
FatReader f; // This holds the information for the file we're play

WaveHC wave; // This is the only wave (audio) object, since we will only play one at a time

#define DEBOUNCE 5 // button debouncer

// here is where we define the buttons that we'll use. button "1" is the first, button "6" is the 6th, etc
byte buttons[] = {14, 15, 16, 17, 18, 19};
// This handy macro lets us determine how big the array up above is, by checking the size
#define NUMBUTTONS sizeof(buttons)
// we will track if a button is just pressed, just released, or 'pressed' (the current state
volatile byte pressed[NUMBUTTONS], justpressed[NUMBUTTONS], justreleased[NUMBUTTONS];

// this handy function will return the number of bytes currently free in RAM, great for debugging! 
int freeRam(void)
 extern int __bss_end; 
 extern int *__brkval; 
 int free_memory; 
 if((int)__brkval == 0) {
 free_memory = ((int)&free_memory) - ((int)&__bss_end); 
 else {
 free_memory = ((int)&free_memory) - ((int)__brkval); 
 return free_memory; 

void sdErrorCheck(void)
 if (!card.errorCode()) return;
 putstring("\n\rSD I/O error: ");
 Serial.print(card.errorCode(), HEX);
 putstring(", ");
 Serial.println(card.errorData(), HEX);

void setup() {
 byte i;
 // set up serial port
 putstring_nl("WaveHC with ");
 Serial.print(NUMBUTTONS, DEC);
 putstring("Free RAM: "); // This can help with debugging, running out of RAM is bad
 Serial.println(freeRam()); // if this is under 150 bytes it may spell trouble!
 // Set the output pins for the DAC control. This pins are defined in the library
 pinMode(2, OUTPUT);
 pinMode(3, OUTPUT);
 pinMode(4, OUTPUT);
 pinMode(5, OUTPUT);
 // pin13 LED
 pinMode(13, OUTPUT);
 // Make input & enable pull-up resistors on switch pins
 for (i=0; i< NUMBUTTONS; i++) {
 pinMode(buttons[i], INPUT);
 digitalWrite(buttons[i], HIGH);
 // if (!card.init(true)) { //play with 4 MHz spi if 8MHz isn't working for you
 if (!card.init()) { //play with 8 MHz spi (default faster!) 
 putstring_nl("Card init. failed!"); // Something went wrong, lets print out why
 while(1); // then 'halt' - do nothing!
 // enable optimize read - some cards may timeout. Disable if you're having problems
// Now we will look for a FAT partition!
 uint8_t part;
 for (part = 0; part < 5; part++) { // we have up to 5 slots to look in
 if (vol.init(card, part)) 
 break; // we found one, lets bail
 if (part == 5) { // if we ended up not finding one :(
 putstring_nl("No valid FAT partition!");
 sdErrorCheck(); // Something went wrong, lets print out why
 while(1); // then 'halt' - do nothing!
 // Lets tell the user about what we found
 putstring("Using partition ");
 Serial.print(part, DEC);
 putstring(", type is FAT");
 Serial.println(vol.fatType(),DEC); // FAT16 or FAT32?
 // Try to open the root directory
 if (!root.openRoot(vol)) {
 putstring_nl("Can't open root dir!"); // Something went wrong,
 while(1); // then 'halt' - do nothing!
 // Whew! We got past the tough parts.
 TCCR2A = 0;
 TCCR2B = 1<<CS22 | 1<<CS21 | 1<<CS20;

//Timer2 Overflow Interrupt Enable
 TIMSK2 |= 1<<TOIE2;



void check_switches()
 static byte previousstate[NUMBUTTONS];
 static byte currentstate[NUMBUTTONS];
 byte index;

for (index = 0; index < NUMBUTTONS; index++) {
 currentstate[index] = digitalRead(buttons[index]); // read the button
 Serial.print(index, DEC);
 Serial.print(": cstate=");
 Serial.print(currentstate[index], DEC);
 Serial.print(", pstate=");
 Serial.print(previousstate[index], DEC);
 Serial.print(", press=");
 if (currentstate[index] == previousstate[index]) {
 if ((pressed[index] == LOW) && (currentstate[index] == LOW)) {
 // just pressed
 justpressed[index] = 1;
 else if ((pressed[index] == HIGH) && (currentstate[index] == HIGH)) {
 // just released
 justreleased[index] = 1;
 pressed[index] = !currentstate[index]; // remember, digital HIGH means NOT pressed
 //Serial.println(pressed[index], DEC);
 previousstate[index] = currentstate[index]; // keep a running tally of the buttons

void loop() {
 byte i;

if (pressed[0]) {
 while (wave.isplaying && pressed[0]) {
 if (pressed[1]) {
 while (wave.isplaying && pressed[1]) {
 if (pressed[2]) {
 while (wave.isplaying && pressed[2]) {
 if (pressed[3]) {
 while (wave.isplaying && pressed[3]) {
 if (pressed[4]) {
 while (wave.isplaying && pressed[4]) {
/* if (pressed[5]) {
 while (wave.isplaying && pressed[5]) {
 if (justpressed[5]) {
 justpressed[5] = 0;

// Plays a full file from beginning to end with no pause.
void playcomplete(char *name) {
 // call our helper to find and play this name
 while (wave.isplaying) {
 // do nothing while its playing
 // now its done playing

void playfile(char *name) {
 // see if the wave object is currently doing something
 if (wave.isplaying) {// already playing something, so stop it!
 wave.stop(); // stop it
 // look in the root directory and open the file
 if (!, name)) {
 putstring("Couldn't open file "); Serial.print(name); return;
 // OK read the file and turn it into a wave object
 if (!wave.create(f)) {
 putstring_nl("Not a valid WAV"); return;
 // ok time to play! start playback;