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Simon Hausmann 70f3f50359 mcu: Add support for automatic font size detection

Continue to support specififying logical font sizes in the compile step
via SLINT_FONT_SIZES, but additionally look for Text/TextInput/Window elements
and extract any constant font sizes
found.

This makes it work out of the box with the printer demo.

2022-04-08 15:11:26 +02:00

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NOTE: This library is an internal crate of the Slint project. This crate should not be used directly by applications using Slint. You should use the slint crate instead.

WARNING: This crate does not follow the semver convention for versioning and can only be used with version = "=x.y.z" in Cargo.toml.

Slint MCU backend

The MCU backend is still a work in progress.

We are currently working on getting demo running with the Raspberry Pi Pico and ST7789 based screen. The Raspberry Pi Pico uses a RP2040 micro-controller which has 264KB of RAM and 2MB of flash memory.

The other backend is the simulator which is a way to test the software rendering backend on desktop.

How to use

In order to use this backend, the final program must depend on both slint and i_slint_backend_mcu. The main.rs will look something like this

#![no_std]
#![cfg_attr(not(feature = "simulator"), no_main)]
slint::include_modules!();

#[i_slint_backend_mcu::entry]
fn main() -> ! {
    i_slint_backend_mcu::init();
    MainWindow::new().run();
    panic!("The event loop should not return");
}

Since i_slint_backend_mcu is at the moment an internal crate not uploaded to crates.io, you must use the git version of slint, slint-build, and i_slint_backend_mcu

[dependencies]
slint = { git = "https://github.com/slint-ui/slint" }
i_slint_backend_mcu = { git = "https://github.com/slint-ui/slint" }
# ...
[build-dependencies]
slint-build = { git = "https://github.com/slint-ui/slint" }

Run the demo:

The simulator

cargo run -p printerdemo_mcu --features=i-slint-backend-mcu/simulator --release

On the Raspberry Pi Pico

You need nightly rust because that's the only way to get an allocator.

Build the demo with:

cargo +nightly build -p printerdemo_mcu --features=mcu-pico-st7789 --target=thumbv6m-none-eabi --release

You should process the file with elf2uf2-rs

cargo install elf2uf2-rs
elf2uf2-rs target/thumbv6m-none-eabi/release/printerdemo_mcu

Then upload the demo to the raspberry pi: push the "bootsel" white button on the device while connecting the micro-usb cable to the device, this connect some storage where you can store the binary.

Or from the command on linux: (connect the device while pressing the "bootsel" button.

# mount the device
udisksctl mount -b /dev/sda1
# upload
elf2uf2-rs -d target/thumbv6m-none-eabi/release/printerdemo_mcu

Using probe-run

This require probe-run (cargo install probe-run) and to connect the pico via a probe (for example another pico running the probe)

Then you can simply run with cargo run

CARGO_TARGET_THUMBV6M_NONE_EABI_LINKER="flip-link" CARGO_TARGET_THUMBV6M_NONE_EABI_RUNNER="probe-run --chip RP2040" cargo +nightly run -p printerdemo_mcu --features=mcu-pico-st7789 --target=thumbv6m-none-eabi --release

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