Halloween: Screaming Cakes!

We all love a good treat when it comes to Halloween, so why not add some shock and horror to your food by making it scream!

BeginnerFull instructions provided30 minutes12

Things used in this project

Hardware components

Teensy 4.1

Teensy Audio Board

Male/Female Jumper Wires

Tin Foil

Software apps and online services

Microsoft Visual Studio 2022

Visual Micro

Story

This can be done using a variety of boards, this guide covers using the Teensy 4.1 with the Audio Shield (Rev.D), and an SD Card to contain the sounds.

To get setup with the Teensy boards, see our guide here.

Code Setup

The example code for this sketch can be downloaded from this location, along with the example WAV file to go on your SD Card.

The project can be uploaded onto the Teensy 4.1 board at this point (see below to change the sounds for your own).

Hardware Setup

Insert the SD Card into the Teensy Audio Shield (with your sound file uploaded).

Fit the Teensy 4.1 onto the Audio Shield using the headers.

Connect your speakers to the 3.5mm connector on the Audio Shield.

Teensy 4.1 with Audio Shield connected to Speakers

Wire pin 31 to the foil beneath your food, either by covering a board in foil, or using a foil tray to put your food upon.

1 / 2 • Jumper Wire connected to Foil

Wire pin 30 to the metal knife/tongs which are used to touch the food.

Plug the speakers in and power up the Teensy board, and when your knife/tongs touch the food, you should hear a scream! 👻😱

Changing the Sounds

The sounds will need to be saved as WAV files, with 16-bit PCM Encoding, at a bit rate of 44100Hz. This can be done with various tools, we have used Audacity to achieve this.

Open your Sound file in Audacity
Right click on the track, and click Format > 32bit float
Right click the track again and click Rate > 44100 Hz
Click File > Export > Export as WAV
Save As Type: WAV (Microsoft)
Set Encoding: Signed 16-bit PCM
Enter the file name and click save
Upload the file to your SD Card
Ensure the name in the sketch matches the file name on the SD Card

The file name needs to be in uppercase 8.3 format, so keep it very simple and short e.g. "TEST1.wav"

Video of it Working

Halloween: Ex-Screamingly Good Treats!

ScreamingCake.ino

// Screaming Cake Example
//
// Three types of output may be used, by configuring the code below.
//
//   1: Digital I2S - Normally used with the audio shield:
//         http://www.pjrc.com/store/teensy3_audio.html

// This also uses the Capacitive Touch Library to detect when the food is touched
// // https://www.pjrc.com/teensy/td_libs_CapacitiveSensor.html
// 
// This example code is in the public domain.
#include <CapacitiveSensor.h>
#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>

CapacitiveSensor   cs_4_2 = CapacitiveSensor(30, 31);        // 10M resistor between pins 4 & 2, pin 2 is sensor pin, add a wire and or foil if desired

AudioPlaySdWav           playWav1;
AudioOutputI2S           audioOutput;

AudioConnection          patchCord1(playWav1, 0, audioOutput, 0);
AudioConnection          patchCord2(playWav1, 1, audioOutput, 1);
AudioControlSGTL5000     sgtl5000_1;

// Use these with the Teensy Audio Shield
#define SDCARD_CS_PIN    10
#define SDCARD_MOSI_PIN  7
#define SDCARD_SCK_PIN   14

void setup() {
    Serial.begin(9600);  

    // Audio connections require memory to work.  For more
    // detailed information, see the MemoryAndCpuUsage example
    AudioMemory(8);

    // Comment these out if not using the audio adaptor board.
    // This may wait forever if the SDA & SCL pins lack
    // pullup resistors
    sgtl5000_1.enable();
    sgtl5000_1.volume(1.0);

    SPI.setMOSI(SDCARD_MOSI_PIN);
    SPI.setSCK(SDCARD_SCK_PIN);
    if (!(SD.begin(SDCARD_CS_PIN))) {
        // stop here, but print a message repetitively
        while (1) {
            Serial.println("Unable to access the SD card");
            delay(500);
        }
    }
}

void playFile(const char* filename)
{
  
    Serial.print("Playing file: ");
    Serial.println(filename);

    // Start playing the file.  This sketch continues to
    // run while the file plays.
    playWav1.play(filename);

    // A brief delay for the library read WAV info
    delay(25);

    // Simply wait for the file to finish playing.
    while (playWav1.isPlaying()) {
        // uncomment these lines if you audio shield
        // has the optional volume pot soldered
        //float vol = analogRead(15);
        //vol = vol / 1024;
        // sgtl5000_1.volume(vol);
    }
}


void loop() {
    int touchReadVal = cs_4_2.capacitiveSensor(30);
    Serial.print("Touch:");
    Serial.println(touchReadVal);
    if (touchReadVal >= 0 && touchReadVal < 30000) {
        playFile("SDTEST1.WAV");  // filenames are always uppercase 8.3 format
    }
    delay(500);

}