Where it all began… A space themed cake competition at work ended up getting a little out of hand when I decided to add some sound effects to my cake.
The Cake
This was a delicious chocolate and caramel overload with three tiers of cake sandwiched with caramel and covered in a thick layer of ganache! See this separate post for the recipe.
The Tron
The iconic red eye of the HAL 9000 was represented by a speaker, connected to an arduino equipped with a “waveshield” capable of playing audio files from an SD card.
At the push of a button the iconic “Also sprach Zarathustra” theme from 2001: A Space Oddessy would play, while another button triggered a series of quotes from the film.
All of the electronics and batteries were concealed under a cakeboard on top of an A4 picture frame, with a few controls exposed on the top.
Arduino Setup
The waveshield arrived in a kit form, so required a moderate amount of soldering. It came with good instructions and examples so once assembled I was able to get it up and running pretty quickly.
Arduino Code
#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 100 // button debouncer byte WavToPlay; // 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); while(1); } void setup() { // set up serial port Serial.begin(9600); putstring_nl("WaveHC with 6 buttons"); 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); // enable pull-up resistors on switch pins (analog inputs) digitalWrite(14, HIGH); digitalWrite(15, HIGH); digitalWrite(16, HIGH); digitalWrite(17, HIGH); digitalWrite(18, HIGH); digitalWrite(19, HIGH); WavToPlay = 0; // 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 sdErrorCheck(); while(1); // then 'halt' - do nothing! } // enable optimize read - some cards may timeout. Disable if you're having problems card.partialBlockRead(true); // 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. putstring_nl("Ready!"); } void loop() { //putstring("."); // uncomment this to see if the loop isnt running switch (check_switches()) { case 1: playfile("ALSO.WAV"); break; case 2: WavToPlay = WavToPlay+1; if(WavToPlay > 8) { WavToPlay = 1; } switch (WavToPlay) { case 1: playcomplete("SORRY1.WAV"); break; case 2: playcomplete("HAL9000.WAV"); break; case 3: playcomplete("DISCON.WAV"); break; case 4: playcomplete("GOODEVE.WAV"); break; case 5: playcomplete("FEEL.WAV"); break; case 6: playcomplete("SORRY2.WAV"); break; case 7: playcomplete("STRESS.WAV"); break; case 8: playcomplete("GOODBYE.WAV"); } break; case 3: wave.stop(); } } byte check_switches() { static byte previous[6]; static long time[6]; byte reading; byte pressed; byte index; pressed = 0; for (byte index = 0; index < 6; ++index) { reading = digitalRead(14 + index); if (reading == LOW && previous[index] == HIGH && millis() - time[index] > DEBOUNCE) { // switch pressed time[index] = millis(); pressed = index + 1; break; } previous[index] = reading; } // return switch number (1 - 6) return (pressed); } // Plays a full file from beginning to end with no pause. void playcomplete(char *name) { // call our helper to find and play this name playfile(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 (!f.open(root, 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 wave.play(); }