waveshare-watch-rs

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100% Rust no_std smartwatch firmware for the Waveshare ESP32-S3-Touch-AMOLED-2.06.

Complete conversion of the original C/C++ project (ESP-IDF + Arduino GFX + LVGL) to a single-binary Rust codebase relying on esp-hal 1.0, esp-rtos, Embassy, and custom drivers for each of the board's peripherals.

The firmware handles the 410×502 QSPI display in 80 MHz DMA, the I2S audio codec, 2.4 GHz WiFi with NTP sync, SD card, capacitive touch, gyroscope, hardware RTC, AXP2101 power management, a launcher with 5 mini-games, a T9 keyboard, an MP3 player (UI), a Smart Home app (HTTP), a sleep/wake mode with an Apple Watch style Always-On Display, and an event-driven main loop based on GPIO interrupts to leave the CPU asleep >99% of the time on the watchface.

---

Hardware target

Waveshare Wiki reference: https://www.waveshare.com/wiki/ESP32-S3-Touch-AMOLED-2.06

Full pinout in src/board.rs.

---

Software stack

Zero C code, zero ESP-IDF components compiled into the final target. The bootloader is esp-bootloader-esp-idf on the loader side only.

---

Architecture

main.rs
│
├── esp_hal::init(CpuClock::_160MHz)
├── PSRAM allocator init
├── esp_rtos::start(timer)         ← Embassy executor
│
├── [Peripherals init] ──── drivers/ + peripherals/
│   ├── Shared I2C bus (RefCell + RefCellDevice)
│   ├── AXP2101 power rails + battery monitor
│   ├── QSPI SPI2 80 MHz DMA 8 KB → Co5300Display
│   ├── PSRAM Framebuffer double buffer (2 × 402 KB)
│   ├── FT3168 touch + GPIO38 INT
│   ├── PCF85063A RTC
│   ├── QMI8658 IMU (power_down by default)
│   ├── SD SPI3 4 MHz
│   ├── ES8311 codec + I2S0 DMA
│   └── WiFi esp-radio + embassy-net DHCPv4 + NTP sync
│
├── [Event-driven loop]
│   │
│   ├── select3(
│   │       Timer::after(adaptive_tick),
│   │       touch_int.wait_for_falling_edge(),
│   │       boot_button.wait_for_falling_edge(),
│   │     ).await
│   │
│   ├── Sensors I/O (gated by screen_state + business need)
│   ├── Touch poll I2C (only if finger is pressed or just lifted)
│   ├── State machine sleep/wake (4 levels + AOD)
│   ├── WiFi auto-disconnect idle >5min
│   └── App state machine
│       ├── Watchface (3 pages: Clock / Sensors / System)
│       ├── Launcher
│       ├── Snake, 2048, Tetris, Flappy, Maze
│       ├── MP3 Player (UI)
│       ├── Settings + T9 keyboard
│       └── SmartHome (buttons → HTTP)

---

Module organization

src/
├── main.rs                 Hardware init + async main loop
├── board.rs                Pinout + display dimensions
│
├── drivers/                Low-level drivers (direct hardware)
│   ├── qspi_bus.rs         QSPI bus quad-mode half-duplex, begin/stream/end
│   ├── co5300.rs           CO5300 init sequence, addr window, set_brightness,
│   │                       display_on/off (MIPI DCS), TEARON
│   └── framebuffer.rs      410×502 RGB565 PSRAM FB, double buffer, flush_vsync
│
├── peripherals/            High-level I2C / SPI / I2S drivers
│   ├── power.rs            AXP2101: battery %, voltage, is_charging, power rails
│   ├── touch.rs            FT3168: read, tracking swipe/tap, SwipeDirection
│   ├── rtc.rs              PCF85063A: get_time, set_time, DateTime
│   ├── imu.rs              QMI8658: read_accel/gyro/temp, power_up/down
│   ├── audio.rs            ES8311: Waveshare registers init, mute/unmute, beep
│   ├── sdcard.rs           Stub wrapper around embedded-sdmmc
│   ├── wifi.rs             WiFi types (scan stub)
│   └── http.rs             HTTP GET/POST client via embassy-net TCP
│
├── ui/                     UI components rendered on DrawTarget<Rgb565>
│   ├── watchface.rs        Clock + gyro ball + battery + FR date + AOD
│   ├── segments.rs         7-segment digits for time
│   ├── pages.rs            Clock / Sensors / System pages
│   ├── launcher.rs         App list, interpolated scroll
│   └── t9_keyboard.rs      Alphanumeric T9 keyboard
│
└── apps/                   Applications (implement the App trait)
    ├── snake.rs            Snake with I2S beep on consume
    ├── game2048.rs         2048 swipe merge
    ├── tetris.rs           Tetris gyro + touch
    ├── flappy.rs           Flappy Bird (direct rendering + framebuffer)
    ├── maze.rs             Maze with IMU ball
    ├── settings.rs         WiFi SSID/password + T9
    ├── mp3player.rs        MP3 player UI (decoding to be wired)
    └── smarthome.rs        Button grid → HTTP GET/POST

---

Power management

The firmware is designed to leave the CPU parked most of the time. The Embassy executor only wakes the core on:

• the GPIO38 touch interrupt (FT3168 in monitor mode)
• the GPIO0 button interrupt
• a periodic timer whose period depends on the current state

Screen states (4 levels + AOD)

On wake via touch/button: immediate return to state 3, framebuffer forced into full redraw.

Adaptive main loop ticks

Extra optimizations

• 160 MHz CPU by default (instead of 240 MHz), ~30% CPU power saving.
• IMU power-down: CTRL7 = 0x00 at boot, power-up only when requested by a consumer.
• Touch I2C polled only when the finger is placed (GPIO38 LOW) or just lifted.
• RTC polled at 1 Hz (instead of 5 Hz before optimization).
• Battery polled at 1/60 Hz (1/300 Hz when the screen is off).
• Conditional Watchface flush: the PSRAM FB is flushed only if needs_render() signals an actual change.
• WiFi auto-disconnect after 5 mins of inactivity: wifi_controller.disconnect_async(); the 2.4 GHz radio is the biggest constant consumer. Automatic reconnect on next wake.
• TE VSync spin limited to 400 iterations (instead of 2000) to avoid wasting cycles when TE doesn't pulse.
• Blocking delays replaced by Timer::after(...).await so the CPU stays parked during button debounces.
• Audio PA amp (GPIO46) held LOW at boot, codec muted (DAC power-down + HP drive off) immediately after init. The amp is pulled HIGH only while writing the beep via DMA, then pulled back down.
• AOD Anti burn-in: the position of the HH:MM block in AOD is shifted by (minutes % 9) - 4 pixels in X and Y, like Apple Watch.

Transition order

touch/button       interaction +0s    state 3 (full)
   └─ +20s idle    ────────────────→  state 2 (dim)
   └─ +40s idle    ────────────────→  state 1 (AOD, if Clock page) or state 0 (otherwise)
   └─ +300s idle   ────────────────→  WiFi disconnect
   └─ +600s idle   ────────────────→  state 0 (full OFF)

touch or button GPIO IRQ             → immediate state 3, WiFi reconnect follows

---

Display pipeline

Embedded-graphics draw calls
         │
         ▼
410×502 u16 RGB565 PSRAM Framebuffer  (402 KB back buffer)
         │
         │  fb.flush() OR fb.flush_vsync(te_pin)
         ▼
Co5300Display::set_addr_window(...)
         │
         ▼
QspiBus::write_pixels()
         │
         ▼
esp-hal SPI2 half_duplex_write(
    DataMode::Quad,             ← 4-bit QSPI mode
    Command::_8Bit(0x12),       ← write memory
    Address::_24Bit(0x003C00),
    dummy = 0,
    buffer,                      ← pixel data in quad mode
)
         │
         ▼
DMA_CH0 → GPIO SIO0..SIO3 @ 80 MHz

• swap_and_flush(): double buffer, for games (Flappy); zero tearing.
• flush_vsync(): single buffer, waits for a TE pulse (GPIO13) before sending pixels.
• flush_region(x, y, w, h): partial update, used by watchface partial updates.

---

Build setup

Prerequisites

• Xtensa ESP Rust toolchain (installed via espup):

  cargo install espup
  espup install
  

  rust-toolchain.toml pins channel = "esp".

• MSVC linker (Windows): needed for host build scripts. Install "Desktop development with C++" via Visual Studio Installer. The link.exe must be in the PATH when running cargo. On this project we typically have:

  export PATH="/c/Program Files/Microsoft Visual Studio/18/Community/VC/Tools/MSVC/14.50.35717/bin/Hostx64/x64:$PATH"
  

• espflash:

  cargo install espflash
  

WiFi credentials

SSID and password are read at compile-time via env!(). They must be defined before building:

# Linux / macOS / Git Bash (Windows)
export WIFI_SSID="MyNetwork"
export WIFI_PASS="MyPassword"

# PowerShell
$env:WIFI_SSID = "MyNetwork"
$env:WIFI_PASS = "MyPassword"

Build

WIFI_SSID="MyNetwork" WIFI_PASS="MyPassword" cargo build --release

The final binary is around 579 KB (full firmware with WiFi stack + games + UI).

Flash + serial monitor

espflash flash --port COM7 --monitor target/xtensa-esp32s3-none-elf/release/waveshare-watch-rs

On Linux: /dev/ttyACM0 or /dev/ttyUSB0 depending on the USB bridge.

Build config

• opt-level = "s" in dev AND release (size optimized).
• lto = true in release (global inlining, reduces size by ~20%).
• 64 KB SRAM heap (for the WiFi stack), 8 MB PSRAM heap (framebuffers + Vecs).

---

Features

Integrated and working

• 410×502 QSPI 80 MHz DMA double-buffer display
• PSRAM framebuffer + DMA flush
• Tearing Effect VSync anti-tearing
• FT3168 touch + iOS-like swipe detection + tap + diagonal rejection
• QMI8658 IMU accel + gyro + temperature with power management
• PCF85063A RTC + NTP sync via embassy-net UDP
• WiFi STA: DHCPv4, NTP, HTTP GET/POST, auto-disconnect idle
• ES8311 audio + I2S DMA (Snake beep)
• SD Card 4 GB detection (FAT32 /mp3 scan in place, stable mount if MBR is valid)
• Watchface 3 pages: Clock (7-segment time + battery + FR date + gyro ball), Sensors, System
• Launcher app list with smooth scroll
• Games: Snake, 2048, Tetris, Flappy Bird, Maze (gyro)
• Settings: WiFi SSID/password fields with T9 keyboard
• SmartHome: configurable 6-button HTTP grid
• MP3 Player: UI (play/pause, prev/next, progress bar)
• Screen sleep/wake 4 levels with minute-by-minute Always-On Display
• Boot button = launcher, swipe up = launcher

Partially wired / stubbed

• MP3 decoding: nanomp3 compiled and as a dependency, UI ready, SD → I2S stream to be wired.
• BLE: esp-radio compiled with stub feature, init disabled due to a panic btdm_controller_init -4 in coex with WiFi (requires additional coex config).
• WiFi scan list: ScanResult types ready, Settings UI shows the field but without scan.
• USB Mass Storage: not wired (copy-from-PC would require usb-device + usbd-storage).
• ESP deep sleep: no esp_hal::system::Sleep; we stay in light sleep via the Embassy executor, sufficient for watch usage.

---

Detailed custom drivers

drivers/qspi_bus.rs: QspiBus

Half-duplex quad-SPI bus for the CO5300. API:

fn write_command(&mut self, cmd: u8)
fn write_c8d8(&mut self, cmd: u8, data: u8)
fn write_pixels(&mut self, pixels: &[u16])
fn begin_pixels(&mut self)
fn stream_pixels(&mut self, pixels: &[u16])
fn end_pixels(&mut self)

Uses esp-hal Spi::half_duplex_write() with Command::_8Bit + Address::_24Bit. DataMode::Single is used for commands, DataMode::Quad for pixels.

drivers/co5300.rs: Co5300Display

Init sequence faithful to the C Arduino Waveshare driver Arduino_CO5300.cpp:

• Hardware reset (10ms low, 120ms high)
• SLPOUT (0x11) + delay 120 ms
• 0xFE 0x00 (vendor register access)
• 0xC4 0x80 (SPI mode control)
• 0x3A 0x55 (RGB565 pixel format)
• 0x53 0x20 (write CTRL display)
• 0x63 0xFF (HBM brightness)
• DISPON (0x29)
• 0x51 0xD0 (brightness)
• 0x35 0x00 (TEARON VBlank only)

Functions: init, set_addr_window, set_brightness, display_on, display_off, bus_mut.

peripherals/audio.rs: Es8311

ES8311 init based on the Waveshare C driver. Critical registers missing in my first attempt:

• 0x00 = 0x1F (reset) → 0x00 = 0x00 → 0x00 = 0x80 (power-on command, initially forgotten)
• Clock coefficients for 4.096 MHz MCLK @ 16 kHz sample rate
• 0x0D = 0x01, 0x0E = 0x02 (power up analog)
• 0x12 = 0x00 (DAC power up), 0x13 = 0x10 (HP drive)
• 0x32 = 0xD9 (volume 85%)

API: init, mute (DAC power-down + HP off + vol 0), unmute, set_volume.

peripherals/power.rs: Axp2101Power

Wrapper around axp2101-embedded for battery monitoring + power rails.

peripherals/touch.rs: Ft3168Touch

Monitor mode (REG_POWER_MODE = 0x01): the chip asserts GPIO38 only on a touch event. Internal state machine to distinguish tap / swipe up/down/left/right with:

• minimum 30 px threshold to qualify a swipe
• 1.5× ratio on the dominant axis to reject diagonal swipes
• tracking start/end coordinates

peripherals/imu.rs: Qmi8658Imu

Init accel ±2g @ 500 Hz, gyro ±512 dps @ 119 Hz, LPF enabled.

fn read_accel() -> AccelData    // m.x, y, z in g
fn read_gyro() -> GyroData      // °/s
fn read_temperature() -> f32    // °C
fn power_up() / power_down()    // CTRL7 0x03 / 0x00

peripherals/rtc.rs: Pcf85063aRtc

BCD read/write of registers 0x04..0x0A. Auto conversion to DateTime { year, month, day, hours, minutes, seconds }.

peripherals/http.rs: http_get / http_post

Minimal HTTP client without external crate: parse URL, TcpSocket::connect, format request manually, custom write_all (handling partial writes), read until close, parse status code + body truncated to 128 bytes.

---

Runtime data flow

On boot

1. esp_hal::init(CpuClock::_160MHz)
2. esp_alloc::psram_allocator!: 8 MB PSRAM heap
3. esp_rtos::start(timg0.timer0): Embassy executor
4. Sequential init of all I2C/SPI/I2S drivers
5. wifi_controller.connect_async().await
6. embassy_net::Stack + StackResources<3>, spawn net_task task
7. Wait for DHCP IP
8. ntp_sync(): UDP to 216.239.35.0:123, parse timestamp, rtc.set_time()
9. Initial watchface render
10. Enter main loop

In the loop

loop {
    // Choose tick based on state
    let tick = match (screen_state, app_state, current_page, gyro_enabled) { ... };

    // Sleep until next event
    select3(
        Timer::after(tick),
        touch_int.wait_for_falling_edge(),
        boot_button.wait_for_falling_edge(),
    ).await;

    // Sensors throttled by need + screen_state
    if need_imu { imu.read_accel(); ... }
    if screen_state >= 2 && now >= next_rtc { rtc.get_time(); ... }
    if now >= next_battery { power.get_battery_percent(); ... }

    // Conditional touch poll (finger placed or just lifted)
    if touch_active { touch.poll(); ... }

    // Sleep/wake state machine → transitions 3→2→1→0
    // WiFi auto-disconnect
    // AOD render path (1x/min) → continue
    // Screen OFF → continue
    // App state machine → render + conditional flush
}

---

Project metrics

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C++ vs Rust comparison

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Conversion history (C++ to Rust)

The original C++ project used:

• ESP-IDF + FreeRTOS
• Arduino GFX for the CO5300
• LVGL for the UI
• ES8311 codec via Arduino driver
• XPowersLib for the AXP2101

Major steps of the rewrite:

1. QSPI bus + CO5300. The hardest part: discovering that esp-hal half_duplex_write supports DataMode::Quad via the Command + Address machinery. Initial bug: using with_miso (input) instead of with_sio1 (output) caused SIO1 to float → all blacks appeared green.

2. AXP2101. Activating the DC1 (3.3 V main) and ALDO1 (panel) rails via registers 0x80 and 0x92, otherwise the screen stays black even with the CO5300 correctly initialized.

3. PSRAM Framebuffer. Alignment issue: the CO5300 is strict on even widths for partial writes. Added even-rounding logic in flush_region. The PSRAM allocator requires features = ["psram"] on esp-hal + esp_alloc::psram_allocator! macro after esp_hal::init.

4. ES8311 Audio. 4 attempts before getting sound: the correct public method to play via I2S is write_dma() (not write() which is private). The init must exactly match the C sequence, particularly the write_reg(0x00, 0x80) after the reset, otherwise the codec stays in power-down.

5. Event-driven loop. Converted from loop { Timer::after(5ms).await; ... } to select3(Timer, touch_edge, button_edge). Gain: CPU wake-ups reduced by ~6000× in screen OFF and ~200× in idle watchface.

6. BLE. Init attempt with esp_radio::ble::BleConnector::new → panic btdm_controller_init returned -4. BLE disabled in Cargo.toml features pending a correct coex configuration.

7. Sleep/wake. Initial bug: the display_on() sequence did DISPON then SLPOUT (incorrect order), so DISPON happened while the panel was still in SLPIN. Fixed to SLPOUT (120 ms) → DISPON (20 ms), standard MIPI DCS order.

---

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Hardware drivers were written from scratch, informed by Waveshare's C/C++ examples and the esp-hal ecosystem.

---

Resources

• Waveshare Wiki: https://www.waveshare.com/wiki/ESP32-S3-Touch-AMOLED-2.06
• esp-hal: https://github.com/esp-rs/esp-hal
• esp-rtos: https://github.com/esp-rs/esp-rtos
• Embassy: https://embassy.dev
• embedded-graphics: https://docs.rs/embedded-graphics
• CO5300 datasheet: provided by Waveshare on the wiki
• AXP2101 datasheet: X-Powers
• ES8311 datasheet: Everest Semiconductor
• QMI8658 datasheet: QST Corporation

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