README.md

rp2040_pico_sdk_playground

Building

git submodule update --init --recursive
export PICO_SDK_PATH=/path/to/your/pico-sdk
mkdir build
cd build
cmake ..
make

More complete info can be extracted from GitHub action script.

Applications

rpi_lcd_test

A simple app demonstrating the use of PIO and DMA for efficient data transfers to a 480x320 TFT display. The graphics library creates a monochromatic image in memory which is expanded to 16-bit color codes in PIO block and transferred via 8-bit parallel interface.

rpi_ws2812_lamp

A simple app controlled by one button, controlling a WS2812 strip/matrix. Can be used to test strips/matrices.

Button press/sequence	Action
Hold	Adjust brightness
Tap and hold	Adjust color
One tap	Toggle 3-minute timer
Two taps	Toggle between 'Off' and 'Max Red'
Three taps	Cycle through presets

rpi_inmp441_fft_demo

Reading audio from a INMP441 MEMS microphone using PIO+DMA, computing fixed point FFT (CMSIS-DSP) and displaying an ASCII spectrogram on serial.

rpi_inmp441_fft_demo.mp4

rpi_inmp441_fft_demo_2.mp4

rpi_tflm_micro_speech_demo

/Keyword Spotting/Visual Wake Words/ on RP2040

TFLM Micro Speech model is ported to Raspberry Pi Pico (RP2040, Cortex-M0+). Sound is from a MEMS I2S microphone (INMP441). The CPU is clocked at 250MHz. Data from the microphone is transferred using PIO+DMA. With this configuration real-time speech analysis is possible (stride is 20ms at 16kHz sample rate and single inference takes ~19ms).

rpi_tflm_micro_speech_demo.mp4

rpi_inmp441_kws

TinyML keyword spotting demo. The model is Shallow RNN architecture with a FastGRNN cell converted to ~200 lines of C code. At 280MHz Core0 is setting up DMA transfers from I2S microphone and doing feature extraction (dc blocking -> preemphasis -> FFT -> power -> log -> Mel filterbank) in frames, nine frames a second.

The core utilization is ~70%. Core1 every 105ms does NN inference which takes about 85ms (77% core utilization).

The microphone (INMP441) connections are as follows:

rpi_lcd_3d_test

tinygl_1b test app (dithered glxgears)

glxgears_1b.mov

rpi_lcd_3d_skull_test

tinygl_1b test app - model exported from Blender.

pitchshifter

Real time /pitch shifter/voice changer/ application. Pitch shifting code generated in Faust. As a bonus there are also vibrato and echo effects. Short button presses cycle through the pitch levels. Long button press between 500ms-2000ms activates and deactivates echo. Button press longer than 2000ms activates the vibrato.

Example recording:

pitch_shifter_test.mov

INMP441 microphone connections are like in the rpi_inmp441_kws application:

Audio output via GPIO PWM pin with a low-pass filter:

LM386 or PAM8403 can be used to amplify further, to connect a speaker. A tact switch needs to be connected between GP13 and GND.