DF mp3 player

Haunted Skeleton

Arduino sketch for an animatronic Halloween skeleton built on an Arduino Uno.

• Plays the songs on the SD card in a random order, different on every power-up. No song repeats until all of them have played; then a new order is drawn.
• When a visitor walks up, the song pauses and one of the voice clips, picked at random but never the same twice in a row, plays with the jaw synced to it, and each arm goes up and back down, one slightly after the other. The song then resumes where it left off.
• The jaw then rests for at least 5 s before it can be triggered again.

Hardware

All pins, angles, distances and timings live in config.hpp. Set DISTANCE_SENSOR there to the sensor you fitted: DistanceSensorType::TIME_OF_FLIGHT (VL53L0X) or DistanceSensorType::SONAR (HC-SR04). The detection range (DETECT_MIN_CM / DETECT_MAX_CM) applies to both.

The VL53L0X runs on 3.3 V and its SDA/SCL pins are not 5 V tolerant. The sketch turns off the Uno's internal pull-ups (which go to 5 V), so the sensor board's own pull-ups to 3.3 V must hold the lines high; if the board has none, fit 4.7 kΩ from SDA and from SCL to 3V3. The bus runs at 100 kHz because 3.3 V only just counts as high for the Uno. Peel off the protective film over the lens.

The 3V3 pin also feeds the DFPlayer and can only supply about 150 mA (Uno R3). If the sensor drops out while music plays loudly, power both from a separate 3.3 V regulator instead.

With the VL53L0X in place of the sonar:

Setup

1. Install the Servo, DFRobotDFPlayerMini (1.0.6) and VL53L0X by Pololu (1.3.1) libraries in the Arduino IDE. The VL53L0X library is needed even when the sonar is selected.
2. Format a FAT32 SD card and copy the songs to its root (they play shuffled, so their order does not matter, but copy them before the voice clips: the module numbers tracks by copy order). Then create a folder ADVERT and copy the voice clips from sd_card/ into it, renamed so each starts with a 4-digit number: 0001_WhoAreYou.mp3, 0002_ComeHere.mp3, ... (the module only reads the first four digits). An advert pauses the song and the song resumes where it left off. Set MP3_SONG_COUNT in config.hpp to the number of songs. After adding, removing or changing a voice clip, regenerate the jaw scripts with python3 tools/make_jaw_script.py (needs numpy and ffmpeg); clip N in sd_card/ must be advert N on the card.
3. Power the servos well: three servos (two lifting arms) can draw more current than the board's 5 V regulator supplies.
4. If the eyes blink 5 times at power-up, the MP3 player or its SD card did not answer: check the wiring and the card. tools/mp3_test tests the player on its own. If they blink 3 times, the VL53L0X did not answer: check its I2C wiring. tools/tof_test tests the sensor on its own.
5. Calibrate MOUTH_CLOSED_DEG / MOUTH_OPEN_DEG and the arm angles and sweep times in config.hpp for your build.

Hardware serial

The DFPlayer is on the Uno's only hardware serial port (pins 0/1). A software serial port would block interrupts for about 1 ms per byte, which stretches the servo pulses and makes the arms jerk past their limits. As a result:

• The Serial Monitor cannot be used by the sketch; anything printed would go to the DFPlayer. Faults are reported by the eye blinks. tools/tof_test still prints to the Serial Monitor; tools/mp3_test shows its results on the eye LEDs instead.
• The USB port shares pins 0/1. If an upload fails, disconnect the module's TX from pin 0 while uploading.

Code layout