cardputer-adv

Board support for the M5Stack Cardputer ADV (ESP32-S3) on esp-hal 1.x: async drivers for its screen, keyboard, motion sensor, speaker, microphone and the rest, all but the microSD card tested on the device.

The screen captured from the device with Frame::screenshot, on a Cardputer ADV photo © M5Stack.

It's for the ADV only. The original Cardputer reads its keyboard as a GPIO matrix rather than through a TCA8418, has no motion sensor, and has different audio, so most of this doesn't apply to it.

Getting started

Install Rust's Xtensa toolchain and the flasher, then try the smallest example, examples/hello.rs, which shows what you type:

cargo install espup espflash
espup install && . ~/export-esp.sh
git clone https://github.com/tszarzynski/cardputer-adv && cd cardputer-adv
cargo run --release --example hello   # with the Cardputer on USB

For an app of your own, copy hello.rs to src/main.rs, with this Cargo.toml:

[package]
name = "my-app"
version = "0.1.0"
edition = "2024"

[dependencies]
cardputer-adv = "0.4"
embassy-executor = "0.10"
embedded-graphics = "0.8"
esp-backtrace = { version = "0.20", features = ["esp32s3", "panic-handler", "println"] }
esp-bootloader-esp-idf = { version = "0.6", features = ["esp32s3"] }
esp-hal = { version = "1.2", features = ["esp32s3", "unstable"] }
esp-println = { version = "0.18", features = ["esp32s3"] }
esp-rtos = { version = "0.4", features = ["embassy", "esp32s3"] }

[profile.release]
debug = 2

and .cargo/config.toml, so cargo run --release builds for the ESP32-S3 and flashes it:

[build]
target = "xtensa-esp32s3-none-elf"

[target.xtensa-esp32s3-none-elf]
runner = "espflash flash --monitor --chip esp32s3"
rustflags = ["-C", "link-arg=-nostartfiles", "-C", "link-arg=-Tlinkall.x", "-C", "link-arg=-Wl,--no-warn-rwx-segments"]

[unstable]
build-std = ["core"]

and rust-toolchain.toml, for the Xtensa toolchain:

[toolchain]
channel = "esp"

examples/hardware.rs uses every part, if you want to see one in a full program.

Hardware

What the Cardputer ADV has, and what this crate covers so far.

API

• display(DisplayPins) sets up the 1.14" ST7789V2 LCD and turns the backlight on. You get it back as a 240×135 RGB565 embedded-graphics DrawTarget, in landscape with the keyboard below, and a Backlight. It draws straight to the panel, so each shape shows as it's drawn. Backlight::set_brightness dims it with 256 Hz PWM on LEDC (as M5GFX does; the LED driver doesn't follow fast PWM); the RGB LED, on the same pin, dims too.
• frame_display(DisplayPins, dma) sets up the same LCD to be fed from a Frame: a 240×135 RGB565 framebuffer (64.8 kB, kept in a static) that you draw into with embedded-graphics. FrameDisplay::flush(&mut frame).await then sends it by DMA, so other tasks run meanwhile.
  • Only pixels whose colour changed are sent: each run of changed rows goes as one rectangle, as wide as its changes. Redrawing the whole frame every time is fine.
  • A whole frame takes 13 ms at 40 MHz. Drawing straight to the panel through display sends a frame in about 28 ms, converting pixel by pixel.
  • FrameDisplay::set_asleep(true).await puts the panel's controller to sleep (a few µA instead of a few mA) with the picture kept in its memory; set_asleep(false) wakes it. Turn the backlight off first.
• keyboard(KeyboardPins).await sets up the 56-key TCA8418 keyboard on I2C, with Shift and Fn layers (keys::KeyInput; the layout is cardputer-adv-keyboard's). Fn + ; . , / gives the arrow keys.
• Keyboard::wait_for_inputs().await sleeps until the TCA8418 pulls its interrupt line (GPIO11) low, then returns the keys pressed.
  • It waits for the low level, not an edge, so events that arrive while you're busy aren't lost.
  • A 1 s fallback poll covers a missed interrupt; missed_interrupts() counts how often that poll was needed.
  • Cancelling it (in a select) loses no key it has read: the next call returns it.
  • Keyboard::is_held(input) says whether a key that types input is down, with or without Shift and Fn (Char('a') and Char('A') are both the A key, Arrow(Up) the ; key): for games, and chords such as Ctrl + C. It's as of the last event read, and wait_for_inputs reads them as they come while it's waiting, releases too.
  • Keyboard::wait_for_events().await waits the same way, and returns keys coming up as well as going down: KeyEvent::Pressed(input) and KeyEvent::Released(input), in order. A release says what its press typed, even if Shift or Fn changed in between: for games, where letting go of a key matters.
  • Keyboard::set_repeat(Some(Repeat::default())) repeats a held key in what wait_for_inputs returns: after 400 ms, then 20 times a second (Repeat::new(delay, interval) for others). The last key pressed repeats, until it's released; modifiers don't. wait_for_events reports only the real presses and releases. It's off until set.
  • KeyInput::char() is the character a key puts in text (Enter is '\n', Tab '\t'); None for the keys that edit, move or modify. KeyInput displays as the key's name (A, Space, Esc, Up, Ctrl), for labels and hints.
  • Keyboard::listen_for_wake(), just before esp-hal's LowPower::sleep_light, makes a key press end the light sleep; wait_for_inputs then reads the key.
• imu(&I2cBus).await finds the BMI270 motion sensor (at 0x68 or 0x69), uploads its configuration (Bosch's, from bmi2) and turns on its accelerometer at ±8 g and 100 Hz. Imu::acceleration().await reads it in milli-g.
• speaker(SpeakerPins) starts a 16-bit, 44.1 kHz I2S stream over DMA to the ES8311 codec, playing silence. codec(&I2cBus).await then turns on the codec's DAC path to the NS4150B amplifier and returns a Codec, whose set_volume(percent).await sets its level. Speaker::run(fill).await keeps the stream fed with the mono samples your closure writes.
  • The buffer holds 23 ms. If fill falls further behind, the stream restarts on silence, so the sound skips rather than stops.
  • Codec::set_output(false) powers the codec's DAC and its path to the amplifier down, and set_output(true) brings them back. Turn it off before the I2S clock stops (in a light sleep): the codec clocks itself from the stream, and the clock stopping and starting clicks in the speaker.
  • Tone::new(Hertz(880), Duration::from_millis(100)) is a beep (embassy-time's Duration, or core's): a square wave (or a triangle, with_waveform(Waveform::Triangle)) at a level (with_level(percent), half the full scale unless set), faded in and out over 2 ms so it doesn't click. tone.fill(samples) writes its samples and then silence, so speaker.run(|samples| beep.fill(samples)) plays it; it's an iterator of samples too, to mix.
  • To avoid skips while anything else holds the CPU for longer (drawing a frame straight to the panel takes about 30 ms), run the speaker on a higher-priority executor, such as esp-rtos's InterruptExecutor.
• i2c(I2cPins) sets up the I2C bus that the keyboard, codec and motion sensor share. Pass it to keyboard_on, imu and codec. keyboard(KeyboardPins) sets the bus up itself, for when the keyboard is all you need.
• audio(AudioPins) starts the speaker's stream and the microphone's together, on the same I2S clocks, and returns an Audio. Once codec has set the codec up, Codec::set_microphone(true) turns its ADC on, and Codec::set_microphone_gain(db) sets its preamp (0–30 dB, in 3 dB steps). Audio::run(fill, take).await plays what fill writes and hands what's heard to take, up to 256 mono samples at a time; the two run together because the microphone runs on the speaker's clocks. A stream that falls more than 23 ms behind restarts, so its sound has a gap.
• Imu::set_gyroscope(true).await turns the BMI270's gyroscope on (±2000 °/s at 100 Hz; it draws about 0.9 mA, so imu leaves it off), and Imu::rotation().await reads it in milli-degrees a second. Uncalibrated it can read several degrees a second at rest (from 0.5 to 9 °/s in different runs on the ADV tested); Imu::calibrate_gyroscope().await, with the Cardputer lying still for about 0.4 s, measures that offset and takes it off from then on.
• Imu::set_mode(ImuMode).await trades the motion sensor's current for noise, in the BMI270 datasheet's power modes. imu starts in ImuMode::Performance: the accelerometer draws 210 µA, 970 µA with the gyroscope. ImuMode::Normal drops the gyroscope's low-noise mode (685 µA with it). ImuMode::LowPower samples in bursts of 4, averaged: the accelerometer draws down to a few µA, both down to 420 µA, and the readings are noisier. That's enough for tilt and shakes, and worth it on battery: at 210 µA, the accelerometer alone is about a fifth of a light sleep's current. Calibrate the gyroscope again after changing mode.
• Imu::motion().await reads the acceleration and the rotation rate together (Motion { acceleration, rotation }), in one transfer: both of the same moment, for combining them, and half the bus traffic of reading them apart.
• Imu::temperature().await reads the BMI270's temperature (Millicelsius, shown as 27.4 °C): the board's, a few degrees above the room's while it runs. It's measured every 1.28 s.
• Imu::set_accelerometer_range(AccelerometerRange).await (±2, 4, 8 or 16 g) and Imu::set_gyroscope_range(GyroscopeRange).await (±125, 250, 500, 1000 or 2000 °/s): a narrower range reads small movements more finely and clips big ones. Readings stay in milli-g and milli-degrees a second, and a gyroscope calibration carries over. Each takes 80 ms: the sensor holds its last reading, in the old range, for up to 60 ms after a change.
• Imu::set_rate(ImuRate).await sets how often both sensors measure, from 25 to 1600 Hz (100 Hz to start): faster catches taps and vibration, and slower draws less in ImuMode::LowPower, where the current follows the rate. Low power averages 4 samples a reading, so it goes up to 200 Hz (asked for 400, the sensor gives 200); asking for more, by rate or by mode, is Error::Unsupported. As after a change of mode, the readings stay as they were for a few tens of milliseconds while the sensor's filter starts again.
• rmt(RMT) sets up the RMT peripheral for the RGB LED and the IR transmitter; give each one of its transmit channels. rgb_led(channel, GPIO21) returns an RgbLed, and RgbLed::set_color(Rgb888).await sets it (black is off). It's powered through the backlight's switch, so it's lit only while the backlight is, and dims with it.
• ir_transmitter(channel, GPIO44) returns an IrTransmitter, which sends on a 38 kHz carrier. NEC codes: send_nec(NecCode { address, command }), send_nec_extended(ExtendedNecCode { … }) for a 16-bit address, and send_nec_repeat for a held button. Any other protocol's (Sony, RC5, Samsung, an air conditioner's), or timings recorded from a remote: send_raw(&[Pulse { mark_us, space_us }, …]), each the carrier on for mark_us µs and then off for space_us µs, up to IrTransmitter::MAX_PULSES (128) pulses.
• button(GPIO0) returns the G0 Button: is_pressed(), wait_for_press().await and wait_for_release().await (debounced), and listen_for_wake() to wake the chip from light sleep, as Keyboard::listen_for_wake does.
  • wait_for_click().await tells a press apart, giving the one button three jobs: Click::Single, Click::Double (two presses within 300 ms), or Click::Long (held for half a second, told while it's still held). A single click is told 300 ms after its release, once no second press has come.
• sd_card(SdCardPins), with the sd-card feature, sets up the microSD card's own SPI bus (SPI3) and returns an SdCard, an embedded-sdmmc BlockDevice. Read and write FAT files through embedded_sdmmc::VolumeManager; the crate re-exports embedded_sdmmc, so the versions match. The card is started on first use (at 400 kHz, then run at 20 MHz), and again after a failed access, so it can be inserted or swapped while the app runs. It's blocking, so a long read holds up its executor.
• board!(p).await sets the whole board up in one call, as a Board: the I2C bus, the keyboard, G0, the battery, and the RMT with the RGB LED and the IR transmitter, ready to use. The display and the audio need a choice (drawing straight to the screen or from a framebuffer; the speaker alone or with the microphone), so it hands over their pins; and it leaves the motion sensor to imu(bus), as it takes 230 ms and draws current. Only the board's fields of p move, so the timers and the radio stay usable, and so do the per-part functions below, for full control.
• Each part's pins come out of esp-hal's Peripherals with a macro named after it: display_pins!(p), i2c_pins!(p), keyboard_pins!(p), speaker_pins!(p), audio_pins!(p), battery_pins!(p) and sd_card_pins!(p). Only those fields move, so the rest of p stays usable. The …Pins structs can still be written out by hand.
• battery(BatteryPins) measures the battery voltage (Battery::voltage(), in Millivolts) on GPIO10 through the board's 2:1 divider, as M5Stack's M5Unified does, and Battery::percent() the charge left (a Percent), by M5Unified's estimate (3.30 V empty, 4.10 V full). The board can't tell whether it's charging: on USB with the power switch on, it reads the charging voltage.

use cardputer_adv::Board;
use embedded_graphics::{pixelcolor::Rgb565, prelude::*};

let Board { display, mut keyboard, bus, .. } = cardputer_adv::board!(p).await?;
let (mut display, mut backlight) = cardputer_adv::display(display)?;
let mut imu = cardputer_adv::imu(bus).await?; // if it's wanted
display.clear(Rgb565::BLACK).expect("LCD"); // mipidsi's own error type
loop {
    for key in keyboard.wait_for_inputs().await? { /* … */ }
}

Part by part, with the motion sensor and the speaker: set the shared bus up first.

use cardputer_adv::{Acceleration, Percent, i2c_pins, speaker_pins};

let bus = cardputer_adv::i2c(i2c_pins!(p))?;
let mut keyboard = cardputer_adv::keyboard_on(bus, p.GPIO11).await?;
let mut imu = cardputer_adv::imu(bus).await?;
let Acceleration { x, y, z } = imu.acceleration().await?; // milli-g

// In a task (ideally on a higher-priority executor):
let mut speaker = cardputer_adv::speaker(speaker_pins!(p))?;
// …and once it's running (the codec clocks itself from the stream):
let mut codec = cardputer_adv::codec(bus).await?;
codec.set_volume(Percent::new(60)).await?;
let Err(error) = speaker.run(|samples| samples.fill(0)).await; // runs until it fails

The microphone, the RGB LED and the IR transmitter:

use cardputer_adv::{Decibels, NecCode, audio_pins};
use embedded_graphics::pixelcolor::{Rgb888, RgbColor};

let mut audio = cardputer_adv::audio(audio_pins!(p))?;
let mut codec = cardputer_adv::codec(bus).await?;
codec.set_microphone_gain(Decibels(24)).await?;
codec.set_microphone(true).await?;
// In a task: silence out, 44.1 kHz mono in.
let Err(error) = audio.run(|out| out.fill(0), |heard| { /* … */ }).await;

let rmt = cardputer_adv::rmt(p.RMT)?;
let mut led = cardputer_adv::rgb_led(rmt.channel0, p.GPIO21)?;
let mut ir = cardputer_adv::ir_transmitter(rmt.channel1, p.GPIO44)?;
led.set_color(Rgb888::GREEN).await?;
ir.send_nec(NecCode { address: 0x00, command: 0x45 }).await?;

With a framebuffer, sent by DMA:

use cardputer_adv::Frame;
use static_cell::ConstStaticCell;

static FRAME: ConstStaticCell<Frame> = ConstStaticCell::new(Frame::new());

let (mut display, _backlight) = cardputer_adv::frame_display(display_pins!(p), p.DMA_CH1)?;
let frame = FRAME.take();
loop {
    let Ok(()) = frame.clear(Rgb565::BLACK); // it can't fail
    // …draw the rest…
    display.flush(frame).await?; // only what changed
}

Requirements

• esp-hal 1.2, with its unstable feature (LEDC, I2S, RMT and light sleep are behind it), on an ESP32-S3.
• The sd-card feature, for the microSD card. It's off by default, so apps without a card don't build embedded-sdmmc.
• The defmt feature, for defmt::Format on Error, if your app logs with defmt.
• An embassy-time driver, for the async parts (the keyboard and the motion sensor, from setting them up on, FrameDisplay::flush, Speaker::run): esp-rtos's, say.
• Display is a mipidsi type; the crate re-exports mipidsi, so you can name its types without depending on it yourself.

Sleeping while the screen is dark

The ESP32-S3 can light-sleep (about 1 mA) and carry on where it left off, woken by a key. In this order, with esp-hal's LowPower:

use esp_hal::{
    rtc_cntl::sleep::{LowPower, RtcSleepConfig},
    time::{Duration, Instant},
};

let mut low_power = LowPower::new(p.LPWR);

// Going dark:
backlight.set_brightness(Percent::ZERO)?;
display.set_asleep(true).await?; // the panel controller sleeps, keeping its picture
codec.set_output(false).await?;  // before the I2S clock stops, or the speaker clicks

// Each time round while dark:
keyboard.listen_for_wake();      // a key press ends the sleep
low_power.set_wakeup_deadline(Instant::now() + Duration::from_millis(250));
low_power.sleep_light(RtcSleepConfig::default()); // returns at the key, or the deadline
// …look at the motion sensor, say, then read keys with wait_for_inputs as usual.

// Lighting up again:
display.set_asleep(false).await?;
codec.set_output(true).await?;
backlight.set_brightness(Percent::FULL)?;

While the chip sleeps its USB is off (no log, no flashing until it wakes), and the embassy clock stops. The speaker's stream runs dry and restarts on silence by itself.

Screenshots

Frame::screenshot() gives what the screen shows as one line of text, for the app to log over USB however it logs: the pixels as runs of one colour, in base64, and the time. tools/screenshots.py (Python's standard library only) finds them in a saved log and writes them out as PNGs, sharp at 3×, each held for as long as it was on the screen; just gif <log> makes a GIF of them with gifski. An app that draws straight to the Display draws through a Mirror, which copies what it draws into a Frame.

use cardputer_adv::Mirror;
use embedded_graphics::{
    mono_font::{MonoTextStyle, ascii::FONT_6X10},
    text::Text,
};

// With a framebuffer: after each flush, say.
display.flush(frame).await?;
log::info!("{}", frame.screenshot());

// Drawing straight to the screen: through a Mirror, into a Frame kept for it.
let style = MonoTextStyle::new(&FONT_6X10, Rgb565::WHITE);
Text::new("Hello", Point::new(0, 10), style)
    .draw(&mut Mirror::new(&mut lcd, frame))
    .expect("LCD");
log::info!("{}", frame.screenshot());

Logging one takes a while (a screen of small text is about 20 kB, which esp-println sends over USB in about 0.1 s), and the app waits for it: animations keep their pace, as they go by the clock, but frames drawn meanwhile aren't seen. esp-println holds interrupts off while it prints, so the speaker's and the microphone's streams stall and restart: screenshots are for the screen, not for sound. just screenshots runs the hardware test with them on, and just gif turns its log into a GIF.

Pins

The I2C bus is async, shared through an async mutex (embassy-sync's, with embassy-embedded-hal's I2cDevices), so the keyboard, the codec and the motion sensor can be used from any executor or core. A task waiting for the bus or a transfer lets the others run, and no transfer holds interrupts off, not even the motion sensor's 8 kB start-up.

Status

Tested on a Cardputer ADV (October 2026): the display, the backlight, the keyboard (with its interrupt line and waking from light sleep), the motion sensor (accelerometer, gyroscope and temperature), the speaker, the microphone, G0, the RGB LED, and IR transmission (as signals; the IR LED's light itself not yet seen). examples/hardware.rs (just hardware) tries each part and shows its readings on the screen.

Not yet tested on hardware:

• The microSD card.
• The battery reading, against a multimeter.

The display settings (panel offset 52/40, 90° rotation, colour inversion) come from working ADV firmware (iwan-inc/cardputer-rust); the codec sequences and the pins from M5Stack's M5Unified, with espp's driver. imu tries both of the BMI270's addresses, 0x68 then 0x69, as sources disagree on which the ADV uses.

Built with cardputer-adv

Backgammon against the CPU or a friend: the dice are thrown with a shake, the checkers slide, and it sleeps when put down. Link coming soon.

The screen captured from the device with Frame::screenshot, on a Cardputer ADV photo © M5Stack.

Documentation

docs.rs can't build for Xtensa, so the API docs are on GitHub Pages instead, built by CI from main. To build them locally, run just doc.

Licence

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE)
• MIT licence (LICENSE-MIT)

at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 licence, shall be dual licensed as above, without any additional terms or conditions.