PicoADK Firmware Template

PicoADK is the audio dev kit for the Raspberry Pi RP2040 (v1) and RP2350 (v2). This template is the firmware starting point: a clean HAL on top of the Pico SDK that hides the silicon differences (FPU, PSRAM, SDIO, M33 DSP intrinsics) so the same audio callback runs on both boards without #ifdefs. Drop in your DSP, pick from a tray of ready-made examples, build either board with one command.

Quickstart

git clone --recursive https://github.com/DatanoiseTV/PicoADK-Firmware-Template
cd PicoADK-Firmware-Template
cmake --preset v2                        # or v1
cmake --build build/v2

The UF2 lands in build/v2/app/picoadk_app.uf2. Hold BOOTSEL, plug in the board, drag-drop. You're running.

#include "picoadk/picoadk.h"
#include <FreeRTOS.h>
#include <task.h>

using namespace picoadk;

void audio(const float* const* /*in*/, float* const* out, std::size_t n, void*) {
    for (std::size_t i = 0; i < n; ++i)
        out[0][i] = out[1][i] = std::sin(2.0f * 3.14159f * 440.0f * i / 48000.0f);
}

int main() {
    HardwareConfig hw;
    hw.audio.sample_rate_hz = 48000;
    hw.midi.inputs          = MidiTransport::Usb | MidiTransport::Uart;
    Hardware::init(hw);
    Audio::set_callback(audio);
    Audio::start();
    vTaskStartScheduler();
}

Boots, plays a 440 Hz sine, accepts MIDI on USB and DIN. That's the whole program.

What's in the box

Audio engine with runtime-configurable sample rate (8 k–192 k), bit depth (16/24/32), block size, direction (out · in · full duplex), and frame format (I²S · left/right justified · TDM4 · TDM8). PIO + DMA, off-IRQ FreeRTOS audio task.

MIDI over USB device, UART (5-pin DIN), and USB host (Launchpad / keyboards via pico_pio_usb) — all three simultaneously through one callback set. NRPN/RPN aggregation, 14-bit pitch bend, MIDI clock, channel-mode messages.

USB composite assembled at runtime — CDC serial debug, USB-MIDI (multi-cable), and MSC exposing internal flash and/or the SD card as separate LUNs. Mix and match.

DSP toolkit. dsp::Real is float on RP2350 (FPU) and Q16 fixed-point on RP2040; same code compiles for both. Module library: BLEP / wavetable / noise oscillators, ADSR, state-variable + ladder filters, saturator, wavefolder, delay (PSRAM-backed), 8-line FDN reverb (PSRAM-backed), compressor.

Sampler — memory-resident or SD-streaming WAV (16/24/32-bit), pitch shift, looping, multisample keymap; SoundFont 2 via TinySoundFont (multisample/loop/release/modulators); embedded SFZ subset parser that builds streaming sources per region. Per-source 4096-frame prefetch ring keeps SD seeks at note-on time only.

PSRAM — TLSF allocator over the v2's 8 MB QSPI PSRAM. Linker section macros (PICOADK_PSRAM_BSS/_DATA), placement-new (PSRAM). Falls back to the system heap on v1 so portable code Just Works.

Storage — SdFat with FAT32 / exFAT / long file names. SDIO 4-bit on v2 (rabbitholecomputing/SDIO_RP2350), SPI on v1.

Display via u8g2 — SSD1306 / SH1106 / SSD1309 over I²C or SPI, full font catalog, gfx::Canvas C++ wrapper for one-liners.

Controls toolkit — MCP3208 SPI ADC, internal SAR ADC, mux banks (CD4051 / 74HC4067), polled quadrature encoders, debounced buttons with hold + double-click.

VoiceLink — wire several PicoADKs together over a 3 Mbaud UART for distributed polyphony / voice cards. Auto-enumerated chain, per-card capacity, oldest/quietest/round-robin allocation. DMA-fed framing keeps the audio thread untouched.

PureData (optional, -DPICOADK_LIBPD=ON) — embed libpd, load patches from flash or SD, route through the audio callback.

FreeRTOS SMP on both boards via the Raspberry Pi-curated kernel fork. xTaskCreatePinnedToCore() works ESP32-style. Stdio routes to UART by default and USB-CDC when you ask for it.

Examples

	What it shows
examples/00_template	Copy-and-edit scaffold — audio + MIDI + controls + USB composite already wired.
examples/01_passthrough	The minimal program — full-duplex passthrough in 25 lines.
examples/02_synth_vult	Original PicoADK Vult monosynth, ported to v3.
examples/03_fx_rack	Stereo delay + Hadamard FDN reverb in parallel; pots morph time / feedback / size / mix; PSRAM-backed buffers on v2.
examples/04_multisampler	Key-mapped piano loaded from SD, 8-voice polyphony with pitch-shift to root.
examples/05_midi_controller	No audio — pots / encoder / button forwarded as USB-MIDI CCs.
examples/06_sf2_player	SoundFont 2 / SFZ player. Drop a default.sf2 (or default.sfz) on the SD card.

cmake --preset v2 -DPICOADK_APP=examples/03_fx_rack
cmake --build build/v2

Build

Preset	Board	Build type
v1	RP2040	Release
v1-debug	RP2040	Debug
v2	RP2350	Release
v2-debug	RP2350	Debug

Useful flags:

Flag	Default	Effect
-DPICOADK_APP=<dir>	examples/02_synth_vult	App folder to build.
-DPICOADK_VULT_REAL=float|fixed	auto	Vult numeric type (float on v2, Q16 on v1).
-DPICOADK_VULT_SAMPLERATE=48000	48000	Sample rate baked into Vult tables.
-DPICOADK_ENABLE_SDFAT=ON	OFF	Pull in SdFat for Storage HAL.
-DPICOADK_ENABLE_SDIO=ON	OFF	Pull in SDIO_RP2350 (v2 only).
-DPICOADK_ENABLE_USB_HOST=ON	OFF	Compile the TinyUSB host stack.
-DPICOADK_LIBPD=ON	OFF	Embed libpd.

VS Code: install the official Raspberry Pi Pico extension. CMakePresets.json and .vscode/ are pre-wired — pick a preset from the status bar.

Hardware

	PicoADK v1	PicoADK v2
MCU	RP2040 — dual M0+	RP2350A — dual M33 + FPU + DCP
Flash	4 MB QSPI	4 MB QSPI
PSRAM	—	8 MB QSPI
SD	SPI	SDIO 4-bit
MIDI in	USB + DIN	USB + DIN + USB host (PIO USB)
Display	SSD1306 I²C	SSD1306 / TFT SPI

PicoADK Hardware repo

Documentation

docs/ARCHITECTURE.md	Layered model, audio pipeline diagram, threading model, memory map, file-by-file map.
docs/HAL.md	Per-subsystem reference with code samples for every public API.
docs/OVERCLOCKING.md	Voltage ladders + System::set_clock_khz() recipe.
CHANGELOG.md	What changed in v3.0.0.
CONTRIBUTING.md	House rules + how to add a HAL subsystem / DSP module.

Pinned dependencies

pico-sdk	2.2.0
pico-extras	sdk-2.2.0
FreeRTOS-Kernel	raspberrypi/FreeRTOS-Kernel (SMP for both boards)
pico-pio-usb	latest
u8g2	latest
TinySoundFont	latest
SDIO_RP2350 / SdFat / libpd	fetched on demand via CMake when the matching -DPICOADK_ENABLE_… flag is on

Status

All six example apps build and link clean for both boards (verified with arm-none-eabi-gcc 14.2); CI builds both targets on every push and runs the host-side DSP unit tests (tests/, 10/10 pass). PIO timing for the new I²S/TDM/SDIO programs and PSRAM init on v2 still need real boards on the bench — the structure and call sites are in place; values that need verification are clearly marked in the source.

The legacy firmware is preserved on the RP235x* branches and on tags. Nothing was removed from there.

---

_{BSD-3-Clause · for people who like their synths to sound exactly like they wanted}