cardputer-adv

Board support for the M5Stack Cardputer ADV (ESP32-S3) on esp-hal 1.x.

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_percent 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) sets up the 56-key TCA8418 keyboard on I2C, with Shift and Fn layers from cardputer-adv-keyboard. Fn + ; . , / gives the arrow keys.
• Keyboard::wait_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.
  • Keyboard::listen_for_wake(), just before esp-hal's LowPower::sleep_light, makes a key press end the light sleep; wait_inputs then reads the key.
• imu(&I2cBus) finds the BMI270 motion sensor (at 0x68 or 0x69), uploads its configuration through bmi2 and turns on its accelerometer at ±8 g and 100 Hz. Imu::acceleration() reads it in milli-g.
• speaker(SpeakerPins) starts a 16-bit, 44.1 kHz I2S stream over DMA to the ES8311 codec, playing silence. enable_codec(&I2cBus) then turns on the codec's DAC path to the NS4150B amplifier and returns a Codec, whose set_volume(percent) 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.
  • 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 enable_codec. keyboard(KeyboardPins) sets the bus up itself, for when the keyboard is all you need.
• battery(BatteryPins) measures the battery voltage (Battery::millivolts()) on GPIO10 through the board's 2:1 divider, as M5Stack's M5Unified does, and Battery::percent() the charge left, 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::{DisplayPins, KeyboardPins};
use embedded_graphics::{pixelcolor::Rgb565, prelude::*};

let (mut display, mut backlight) = cardputer_adv::display(DisplayPins {
    spi: p.SPI2, sck: p.GPIO36, mosi: p.GPIO35, cs: p.GPIO37,
    dc: p.GPIO34, reset: p.GPIO33, backlight: p.GPIO38, ledc: p.LEDC,
})?;
let mut keyboard = cardputer_adv::keyboard(KeyboardPins {
    i2c: p.I2C0, sda: p.GPIO8, scl: p.GPIO9, interrupt: p.GPIO11,
})?;
display.clear(Rgb565::BLACK).expect("LCD"); // mipidsi's own error type
loop {
    for key in keyboard.wait_inputs().await? { /* … */ }
}

With the motion sensor and the speaker, set the shared bus up first:

use cardputer_adv::{I2cPins, SpeakerPins};

let bus = cardputer_adv::i2c(I2cPins { i2c: p.I2C0, sda: p.GPIO8, scl: p.GPIO9 })?;
let mut keyboard = cardputer_adv::keyboard_on(bus, p.GPIO11)?;
let mut imu = cardputer_adv::imu(bus)?;
let [x, y, z] = imu.acceleration()?; // milli-g

// In a task (ideally on a higher-priority executor):
let mut speaker = cardputer_adv::speaker(SpeakerPins {
    i2s: p.I2S0, dma: p.DMA_CH0, bclk: p.GPIO41, ws: p.GPIO43, dout: p.GPIO42,
})?;
// …and once it's running (the codec clocks itself from the stream):
let mut codec = cardputer_adv::enable_codec(bus)?;
codec.set_volume(60)?;
let Err(error) = speaker.run(|samples| samples.fill(0)).await; // runs until it fails

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(pins, p.DMA_CH1)?;
let frame = FRAME.take();
loop {
    frame.clear(Rgb565::BLACK)?; // Infallible
    // …draw the rest…
    display.flush(frame).await?; // only what changed
}

Requirements

• esp-hal 1.2, with its unstable feature (LEDC, I2S and light sleep are behind it), on an ESP32-S3.
• An embassy-time driver, for the async parts (Keyboard::wait_inputs, 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};

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

// Going dark:
backlight.set_percent(0)?;
display.set_asleep(true).await?; // the panel controller sleeps, keeping its picture
codec.set_output(false)?;        // 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(esp_hal::time::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_inputs as usual.

// Lighting up again:
display.set_asleep(false).await?;
codec.set_output(true)?;
backlight.set_percent(100)?;

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.

Pins

The I2C bus is a critical_section::Mutex, shared by embedded-hal-bus's CriticalSectionDevices, so the keyboard, the codec and the motion sensor can be used from any executor or core. Each transfer holds the critical section, which delays interrupts by about 0.3 ms for a key or motion read. The motion sensor's start-up holds it for 3 ms per 128-byte burst.

Status

The display settings (panel offset 52/40, 90° rotation, colour inversion) come from working ADV firmware (iwan-inc/cardputer-rust). The display and the keyboard, including its interrupt line, work on a Cardputer ADV (tested October 2026). So do the motion sensor and the speaker. imu tries the BMI270's two addresses, 0x68 then 0x69, because sources disagree on which one the ADV uses (espp says 0x68, oxstack 0x69). The ES8311 sequence is M5Unified's Cardputer ADV speaker enable, as espp's driver uses it. The battery reading is new and not yet checked against a multimeter.

Documentation

docs.rs can't build for Xtensa, so the API docs aren't there: build them with the esp toolchain (cargo +esp doc --target xtensa-esp32s3-none-elf), or read this README and the source.

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.