Build Instructions

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• 1

  Concept:

  The project is a slight modification of talking clock, but in this case, power is activated by a PIR sensor. When a person moves near the critter, a random sound is played. Raspberry Pi Pico was chosen for the 3 following reasons:

  • There’s no need to install software for initial firmware download
  • Onboard memory 2 MegaBytes of flash can store some amount of sounds without requiring external memory
  • Can be powered by 2xAA batteries without additional components

  Rpi Pico draws about 1.6 mA in it’s lowest power mode (deep sleep). Seems not much, but is too high for a battery powered circuit, because they will exhaust in around two months. For that reason an external power circuit that can shut off the board completely was added. After that, power consumption lowered to 70 uA, so batteries will last for a year.

  The Rpi Pico acts as sound storage and player.

• 2

  Software:

  Right after power on, Rpi Pico puts a low level on the GPIO that is wired to the power circuit to keep it powered, then decides which file should be played, and after the sound finishes, a high level is put on the GPIO powering off the Pico. Additionally a light sensor is read to not play sound when is dark (night).

  Sound files are played randomly, one by one on each power on.

• 3

  PECULIARITIES OF THE SDK C/C++ VERSION:

  Sounds to be played must be converted first to WAV format 16 bit mono @ 44100 Hz, then converted to C arrays[] before compiling. The application uses a PWM via digital output and interrupts to play sounds.

  The program execution starts almost immediately after power on. The main disadvantage of the application for now, it only supports .WAV files which are big, and cannot be changed without recompiling code

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