Stefan Wagner's ATtiny Voice Changer Is a Compact Open Source Toy for Pitch-Shifting Audio
Designed to shift up or down on-demand, this open hardware board makes the most of the ATtiny412's ADC and DAC capabilities.
Stefan Wagner is continuing to experiment with Microchip's ATtiny microcontroller family, releasing a compact open source board with an electret microphone designed to shift the pitch of your voice — or any other sounds it can pick up.
"The ATtiny412 Voice Changer is a simple device for changing the pitch of speech and other audio signals," Wagner writes of his latest design. "An electret microphone is installed for audio input, and a small loudspeaker can be connected directly to the board for output."
The surprisingly compact board is made up of very few components: There's the electret microphone at one end, and a low-cost Texas Instruments LMV358 rail-to-rail dual operational amplifier (op-amp). "The first op-amp amplifies the weak signal from the electret microphone," Wagner explains.
"The output of the first op-amp is connected to the ATtiny's analog-to-digital converter (ADC), which samples the amplified audio signal," Wagner continues. "This signal is modified by the ATtiny and output via its digital-to-analog converter (DAC). Since the DAC cannot drive a load directly, the signal is amplified by the LMV358's second OpAmp, which is configured as a voltage follower/buffer. The output of this OpAmp drives the speaker through a coupling capacitor (C2)."
Firmware running on the ATtiny process the audio according to settings controlled by three buttons on the board — allowing the pitch to be shifted upwards or downwards as required. A physical power switch avoids any phantom noise when you're done experimenting with the board.
This isn't Wagner's first foray into the world of ATtiny microcontrollers and audio: We've previously looked at the Pocket Radio, a neat project which puts a single-chip FM tuner and ATtiny microcontroller into a 3D-printed housing with 40mm speaker, amplifier, and a user interface running on a color OLED display panel.
Design files and source code for the Voice Changer are available on Wagner's GitHub repository, under the reciprocal Creative Commons Attribution-ShareAlike 3.0 Unported license.