MCU: ESP32

The gallery as ESP32 firmware: two boards on two architectures, running the same screens the desktop simulator opens and the RP2040 binaries flash. Both images build and link; neither board has been run, and there is no panel driver — Panel::present is where one goes, and docs/hardware.md says why it is marked rather than faked.

Binary	Board	Chip	Target
`x3`	Xteink X3	ESP32-C3	`riscv32imc-unknown-none-elf`
`sticky`	Seeed Sticky	ESP32-S3	`xtensa-esp32s3-none-elf`

Every document in this repository is listed in docs/README.md.

Using it

For a firmware, using it is building it and flashing it. --features is not optional: the chip is a feature of esp-hal rather than a target, so two binaries in one crate cannot each choose their own, and --all-features is two chips at once.

cargo build --release --bin x3 --features x3 --target riscv32imc-unknown-none-elf

. ~/export-esp.sh   # the Sticky's linker, on PATH for this shell
cargo +esp build --release --bin sticky --features sticky --target xtensa-esp32s3-none-elf

.cargo/config.toml names espflash as the runner for both targets, so cargo run flashes the board and opens the serial monitor, where the firmware reports its ink count on every repaint:

cargo run --release --bin x3 --features x3 --target riscv32imc-unknown-none-elf

. ~/export-esp.sh
cargo +esp run --release --bin sticky --features sticky --target xtensa-esp32s3-none-elf

The screens come from xpui-gallery, the board's measurements from xpui-boards, the painting from xpui-backends' embedded_graphics, and the framework from xpui. Nothing depends on this repository: it is a leaf, an image for two boards.

Requirements

The X3 builds on stable Rust. rust-toolchain.toml lists riscv32imc-unknown-none-elf, so rustup installs it on the first cargo call.
The Sticky needs Espressif's compiler fork. Xtensa is not a target stable Rust has: cargo install espup && espup install puts the esp toolchain and its linker in place, and cargo +esp selects it. core is built from source on that path. espup does not touch your shell, so . ~/export-esp.sh in each new one, or the build stops at linker `xtensa-esp32s3-elf-gcc` not found. The gate finds that linker itself; a cargo line does not.
Flashing needs espflash: cargo install espflash. Both boards flash over USB with no probe.

Checking it

./build-and-test.sh          # format, lint for RISC-V, the prose, and the tutorial
./build-and-test.sh all      # plus linking both images

The checks themselves are in xtask/ — this repository's own list, in Rust, holding nothing it does not run. ./build-and-test.sh fix formats in place first. The Xtensa image links only where the fork is installed, and the gate says so when it is not. How a change is reviewed is in docs/contributing.md.

Where it sits

Every arrow is a dependency in a Cargo.toml, and they all point inward toward xpui, which depends on nothing at all. That is the rule the organisation is arranged around: a backend can be written without the framework knowing it exists, and a firmware reaches whatever it needs directly rather than through whoever happens to sit above it.