acid/firmware/acid-firmware/src/main.rs

//! TODO:
//! * GUI event dispatch.
//! * Async interrupt handling of keyboard input. Reduces LCD glitching.
//! * Attempt to reduce the size of the framebuffer to 240x960 by changing the front/back porch of
//!   the LCD driver. Reduces LCD glitching.
//! * Bounce buffers to get rid of glitching completely.
//!   https://esp32.com/viewtopic.php?t=28230
//!   https://esp32.com/viewtopic.php?f=12&t=26793&start=20#p95677
#![no_std]
#![no_main]
#![feature(allocator_api)]
#![feature(macro_metavar_expr)]
#![feature(c_variadic)]
#![feature(c_size_t)]
#![feature(debug_closure_helpers)]

extern crate alloc;

use core::alloc::Layout;
use core::cell::RefCell;
use core::sync::atomic::{AtomicBool, Ordering};

use alloc::boxed::Box;
use alloc::collections::vec_deque::VecDeque;
use alloc::sync::Arc;
use alloc::vec;
use embassy_embedded_hal::adapter::BlockingAsync;
use embassy_embedded_hal::flash::partition::Partition;
use embassy_executor::Spawner;
use embassy_sync::blocking_mutex::raw::CriticalSectionRawMutex;
use embassy_sync::channel::Channel;
use embassy_sync::mutex::Mutex;
use embassy_sync::signal::Signal;
use embassy_time::{Duration, Timer};
use esp_alloc::{HeapRegion, MemoryCapability};
use esp_hal::Blocking;
use esp_hal::clock::CpuClock;
use esp_hal::dma::{BurstConfig, DmaDescriptor, DmaTxBuf, ExternalBurstConfig};
use esp_hal::gpio::{Flex, Input, InputConfig, Level, Output, OutputConfig, Pull};
use esp_hal::i2c::master::{I2c, I2cAddress};
use esp_hal::interrupt::software::SoftwareInterruptControl;
use esp_hal::lcd_cam::LcdCam;
use esp_hal::lcd_cam::lcd::dpi::Dpi;
use esp_hal::mcpwm::{McPwm, PeripheralClockConfig};
use esp_hal::psram::{FlashFreq, PsramConfig, PsramSize, SpiRamFreq, SpiTimingConfigCoreClock};
use esp_hal::ram;
use esp_hal::rng::TrngSource;
use esp_hal::sha::ShaBackend;
use esp_hal::system::Stack;
use esp_hal::timer::timg::TimerGroup;
use esp_rtos::embassy::Executor;
use esp_storage::FlashStorage;
use log::{error, info, warn};
use rmk::channel::{CONTROLLER_CHANNEL, ControllerSub};
use rmk::config::{BehaviorConfig, PositionalConfig, RmkConfig, StorageConfig, VialConfig};
use rmk::controller::{Controller, EventController};
use rmk::debounce::default_debouncer::DefaultDebouncer;
use rmk::event::ControllerEvent;
use rmk::hid::Report;
use rmk::input_device::Runnable;
use rmk::join_all;
use rmk::keyboard::Keyboard;
use rmk::storage::async_flash_wrapper;
use rmk::types::action::{Action, KeyAction};
use rmk::{initialize_keymap_and_storage, run_devices, run_rmk};
use slint::platform::software_renderer::Rgb565Pixel;
use static_cell::StaticCell;
use {esp_alloc as _, esp_backtrace as _};

use crate::keymap::create_hid_report_interceptor;
use crate::logging::LOG_LEVEL_FILTER;
use crate::matrix::IoeMatrix;
use crate::peripherals::st7701s::St7701s;
use crate::ui::backend::{FramebufferPtr, SlintBackend};
use crate::vial::{CustomKeycodes, VIAL_KEYBOARD_DEF, VIAL_KEYBOARD_ID};

mutually_exclusive_features::none_or_one_of!["usb-log", "alt-log", "rtt-log"];

mod crypto;
mod db;
mod ffi;
mod keymap;
mod logging;
mod matrix;
mod peripherals;
mod ui;
mod util;
mod vial;

#[cfg(feature = "alt-log")]
mod console;

// This creates a default app-descriptor required by the esp-idf bootloader.
// For more information see: <https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/system/app_image_format.html#application-description>
esp_bootloader_esp_idf::esp_app_desc!();

// Memory allocation regions.
// These can be debugged using `xtensa-esp32s3-elf-size -A <path-to-binary>`.
// A panic such as `memory allocation of 3740121773 bytes failed` is caused by a heap overflow. The size is `DEEDBAAD` in hex.

/// Total heap size
const HEAP_SIZE: usize = 112 * 1024;
/// Size of the app core's stack
const STACK_SIZE_CORE_APP: usize = 80 * 1024;

// const FRAME_DURATION_MIN: Duration = Duration::from_millis(40); // 25 FPS
const FRAME_DURATION_MIN: Duration = Duration::from_millis(100); // 10 FPS

pub static PSRAM_ALLOCATOR: esp_alloc::EspHeap = esp_alloc::EspHeap::empty();

static KEYBOARD_REPORT_PROXY: Channel<CriticalSectionRawMutex, Report, 16> = Channel::new();
static LCD_ENABLED: AtomicBool = AtomicBool::new(false);

/// Used to signal that MCU is ready to submit the framebuffer to the LCD.
static SIGNAL_LCD_SUBMIT: Signal<CriticalSectionRawMutex, ()> = Signal::new();

/// Used to signal that the MCU is ready to render the GUI.
static SIGNAL_UI_RENDER: Signal<CriticalSectionRawMutex, ()> = Signal::new();

#[esp_rtos::main]
async fn main(_spawner: Spawner) {
    let config = esp_hal::Config::default()
        .with_cpu_clock(CpuClock::max())
        .with_psram(PsramConfig {
            size: PsramSize::AutoDetect,
            core_clock: Some(SpiTimingConfigCoreClock::SpiTimingConfigCoreClock80m),
            flash_frequency: FlashFreq::default(),
            ram_frequency: SpiRamFreq::Freq80m,
        });
    let peripherals: esp_hal::peripherals::Peripherals = esp_hal::init(config);

    #[cfg(feature = "usb-log")]
    let console_task = logging::usb::setup_logging();
    #[cfg(feature = "alt-log")]
    let console_task =
        logging::uart::setup_logging(peripherals.UART2, peripherals.GPIO12, peripherals.GPIO5);
    #[cfg(feature = "rtt-log")]
    let console_task = logging::rtt::setup_logging();

    // Use the internal DRAM as the heap.
    // Memory reclaimed from the esp-idf bootloader.
    const HEAP_SIZE_RECLAIMED: usize = const {
        let range = esp_metadata_generated::memory_range!("DRAM2_UNINIT");
        range.end - range.start
    };

    esp_alloc::heap_allocator!(#[ram(reclaimed)] size: HEAP_SIZE_RECLAIMED);
    esp_alloc::heap_allocator!(size: HEAP_SIZE - HEAP_SIZE_RECLAIMED);
    info!("Heap initialized! {:#?}", esp_alloc::HEAP.stats());

    // Initialize the PSRAM allocator.
    {
        let (psram_offset, psram_size) = esp_hal::psram::psram_raw_parts(&peripherals.PSRAM);
        unsafe {
            PSRAM_ALLOCATOR.add_region(HeapRegion::new(
                psram_offset,
                psram_size,
                MemoryCapability::External.into(),
            ));
        }
        info!(
            "PSRAM allocator initialized with capacity of {} MiB!",
            psram_size / 1024 / 1024
        );
    }

    // let mut io = Io::new(peripherals.IO_MUX);
    // io.set_interrupt_handler(interrupt_handler);

    // info!("IO Mux initialized!");

    // Enable pull-up on GPIO0 to prevent booting into download mode.
    let gpio0 = Output::new(
        peripherals.GPIO0,
        Level::High,
        OutputConfig::default().with_pull(Pull::Up),
    );

    // Enable LDO2
    let _ = Output::new(peripherals.GPIO17, Level::High, OutputConfig::default());

    // Enable antenna
    let _ = Output::new(peripherals.GPIO11, Level::Low, OutputConfig::default());

    // TODO: Use PWM to control the pwm_pin.
    let mut _pwm = McPwm::new(peripherals.MCPWM0, PeripheralClockConfig::with_prescaler(1));
    let mut _pwm_pin = Output::new(peripherals.GPIO21, Level::High, OutputConfig::default());

    let mut sha_backend = ShaBackend::new(peripherals.SHA);
    let _sha_driver_handle = sha_backend.start();

    let timg0 = TimerGroup::new(peripherals.TIMG0);
    let software_interrupt = SoftwareInterruptControl::new(peripherals.SW_INTERRUPT);
    esp_rtos::start(
        timg0.timer0, /*, software_interrupt.software_interrupt0 */
    );

    info!("ESP-RTOS started!");

    // Enable the TRNG source, so `Trng` can be constructed.
    let _trng_source = TrngSource::new(peripherals.RNG, peripherals.ADC1);

    #[cfg(feature = "ble")]
    let mut host_resources = rmk::HostResources::new();
    #[cfg(feature = "ble")]
    let stack = {
        use bt_hci::controller::ExternalController;
        use esp_radio::{Controller as RadioController, ble::controller::BleConnector};

        let mut rng = esp_hal::rng::Trng::try_new().unwrap();
        static RADIO: StaticCell<RadioController<'static>> = StaticCell::new();
        let radio = RADIO.init(esp_radio::init().unwrap());
        let bluetooth = peripherals.BT;
        let connector = BleConnector::new(radio, bluetooth, Default::default()).unwrap();
        let controller: ExternalController<_, 20> = ExternalController::new(connector);
        let central_addr = [0x18, 0xe2, 0x21, 0x80, 0xc0, 0xc7];
        let ble_stack =
            rmk::ble::build_ble_stack(controller, central_addr, &mut rng, &mut host_resources)
                .await;

        info!("BLE stack for RMK built!");

        ble_stack
    };

    // Initialize USB
    #[cfg(not(feature = "no-usb"))]
    let usb_driver = {
        use esp_hal::otg_fs::Usb;
        use esp_hal::otg_fs::asynch::{Config, Driver};

        static EP_MEMORY: StaticCell<[u8; 1024]> = StaticCell::new();
        let ep_memory = EP_MEMORY.init_with(|| [0_u8; _]);
        let usb = Usb::new(peripherals.USB0, peripherals.GPIO20, peripherals.GPIO19);
        // Create the driver, from the HAL.
        let config = Config::default();
        let driver = Driver::new(usb, ep_memory, config);

        info!("USB driver for RMK built!");

        driver
    };

    // Initialize the flash
    static FLASH: StaticCell<Mutex<CriticalSectionRawMutex, BlockingAsync<FlashStorage>>> =
        StaticCell::new();
    let flash = FLASH.init_with(|| {
        let flash = FlashStorage::new(peripherals.FLASH)
            // Flash memory may not be written to while another core is executing from it.
            // By default, `FlashStorage` is configured to abort the operation and log an error message.
            // However, it can also be configured to auto-park the other core, such that writing to
            // flash succeeds.
            // Alternatively, XiP from PSRAM could be used along with the `multicore_ignore` strategy,
            // to avoid having to park the other core, which could result in better performance.
            // Invalid configuration would then present itself as freezing/UB.
            .multicore_auto_park();

        Mutex::<CriticalSectionRawMutex, _>::new(async_flash_wrapper(flash))
    });
    const FLASH_SIZE_TOTAL: u32 = 16 * 1024 * 1024;
    const FLASH_PART_FIRMWARE_OFFSET: u32 = 0;
    const FLASH_PART_FIRMWARE_SIZE: u32 = 0x3f0000;
    const FLASH_PART_RMK_OFFSET: u32 = FLASH_PART_FIRMWARE_OFFSET + FLASH_PART_FIRMWARE_SIZE;
    const FLASH_PART_RMK_SIZE_IN_SECTORS: u32 = 16;
    const FLASH_PART_RMK_SIZE: u32 = FLASH_PART_RMK_SIZE_IN_SECTORS * FlashStorage::SECTOR_SIZE;
    const FLASH_PART_ACID_OFFSET: u32 = FLASH_PART_RMK_OFFSET + FLASH_PART_RMK_SIZE;
    const FLASH_PART_ACID_SIZE: u32 = FLASH_SIZE_TOTAL - FLASH_PART_ACID_OFFSET;
    let flash_part_rmk = Partition::new(flash, FLASH_PART_RMK_OFFSET, FLASH_PART_RMK_SIZE);
    let flash_part_acid = Partition::new(flash, FLASH_PART_ACID_OFFSET, FLASH_PART_ACID_SIZE);

    info!("Flash memory configured!");

    let sck = Output::new(peripherals.GPIO36, Level::High, OutputConfig::default());
    let mosi = Flex::new(peripherals.GPIO35);
    let cs = Output::new(peripherals.GPIO6, Level::High, OutputConfig::default());

    let lcd = LcdCam::new(peripherals.LCD_CAM).lcd;
    let unconfigured_dpi = Dpi::new(lcd, peripherals.DMA_CH2, Default::default())
        .unwrap()
        .with_de(peripherals.GPIO37)
        .with_pclk(peripherals.GPIO34)
        .with_hsync(peripherals.GPIO44)
        .with_vsync(peripherals.GPIO43)
        // Blue
        .with_data0(peripherals.GPIO38)
        .with_data1(peripherals.GPIO39)
        .with_data2(peripherals.GPIO40)
        .with_data3(peripherals.GPIO41)
        .with_data4(peripherals.GPIO42)
        // Green
        .with_data7(peripherals.GPIO13)
        .with_data8(peripherals.GPIO14)
        .with_data9(peripherals.GPIO15)
        .with_data10(peripherals.GPIO16)
        // Red
        .with_data11(gpio0)
        .with_data12(peripherals.GPIO1)
        .with_data13(peripherals.GPIO2)
        .with_data14(peripherals.GPIO3)
        .with_data15(peripherals.GPIO4);

    #[cfg(not(feature = "alt-log"))]
    let unconfigured_dpi = unconfigured_dpi
        // Green
        .with_data5(peripherals.GPIO5)
        .with_data6(peripherals.GPIO12);

    let st7701s = St7701s::new(sck, mosi, cs, unconfigured_dpi).await;

    info!("ST7701S-based LCD display initialized!");

    // RMK config
    let vial_config = VialConfig::new(VIAL_KEYBOARD_ID, VIAL_KEYBOARD_DEF, &[(0, 0), (1, 1)]);
    let storage_config = StorageConfig {
        start_addr: 0,
        num_sectors: FLASH_PART_RMK_SIZE_IN_SECTORS as u8,
        ..Default::default()
    };
    let rmk_config = RmkConfig {
        vial_config,
        storage_config,
        ..Default::default()
    };

    // Initialze keyboard stuffs
    // Initialize the storage and keymap
    let mut default_keymap = keymap::get_default_keymap();
    let mut behavior_config = BehaviorConfig::default();
    let mut per_key_config = PositionalConfig::default();
    let (keymap, mut storage) = initialize_keymap_and_storage(
        &mut default_keymap,
        flash_part_rmk,
        &storage_config,
        &mut behavior_config,
        &mut per_key_config,
    )
    .await;

    info!("Initialized keymap and storage for RMK!");

    // Initialize the matrix and keyboard
    const I2C_ADDR_MATRIX_LEFT: I2cAddress = I2cAddress::SevenBit(0b0100000);
    const I2C_ADDR_MATRIX_RIGHT: I2cAddress = I2cAddress::SevenBit(0b0100001);

    let i2c = I2c::new(peripherals.I2C0, Default::default())
        .unwrap()
        .with_sda(peripherals.GPIO8)
        .with_scl(peripherals.GPIO9);

    let matrix_interrupt_low = Input::new(peripherals.GPIO7, InputConfig::default());

    let mut matrix = IoeMatrix::new(
        matrix_interrupt_low,
        i2c.into_async(),
        DefaultDebouncer::new(),
        [I2C_ADDR_MATRIX_LEFT, I2C_ADDR_MATRIX_RIGHT],
    )
    .await;
    let mut keyboard = Keyboard::new(&keymap); // Initialize the light controller

    info!("Keyboard initialized!");

    static FRAMEBUFFER: StaticCell<Framebuffer> = StaticCell::new();
    let framebuffer = FRAMEBUFFER.init(Framebuffer::new(
        360 + /* TODO: Figure out why more bytes are needed: */ 8,
        960,
    ));

    info!("Framebuffer created!");

    // let window_size = [framebuffer.width, framebuffer.height];
    let window_size = [framebuffer.height, framebuffer.width];
    let framebuffer_ptr = FramebufferPtr(framebuffer.as_target_pixels() as _);

    static SECOND_CORE_STACK: StaticCell<Stack<STACK_SIZE_CORE_APP>> = StaticCell::new();
    let second_core_stack = SECOND_CORE_STACK.init(Stack::new());
    esp_rtos::start_second_core(
        peripherals.CPU_CTRL,
        software_interrupt.software_interrupt0,
        software_interrupt.software_interrupt1,
        second_core_stack,
        move || {
            // static EXECUTOR: StaticCell<InterruptExecutor<2>> = StaticCell::new();
            // let exec = EXECUTOR.init(InterruptExecutor::new(
            //     software_interrupt.software_interrupt2,
            // ));
            // let spawner = exec.start(Priority::Priority3);
            // spawner.must_spawn(run_renderer_task());
            static EXECUTOR: StaticCell<Executor> = StaticCell::new();
            let executor: &mut Executor = EXECUTOR.init(Executor::new());
            executor.run(|spawner| {
                let slint_backend = SlintBackend {
                    // peripherals: RefCell::new(Some(peripherals)),
                    window_size,
                    window: RefCell::new(None),
                    framebuffer: framebuffer_ptr,
                    quit_event_loop: Default::default(),
                    events: Arc::new(critical_section::Mutex::new(RefCell::new(VecDeque::new()))),
                };
                spawner.must_spawn(ui::run_renderer_task(slint_backend, flash_part_acid));
            });
        },
    );

    info!("Second core started!");

    let mut user_controller = UserController::new();

    info!("Awaiting on all tasks...");

    // TODO: Probably want to select! instead and re-try.
    join_all![
        run_alloc_stats_reporter(),
        // We currently send the framebuffer data using the main core, which does not seem to slow
        // down the rest of the tasks too much.
        run_lcd(st7701s, framebuffer),
        run_devices! (
            (matrix) => rmk::channel::EVENT_CHANNEL,
        ),
        keyboard.run(), // Keyboard is special
        run_rmk(
            &keymap,
            #[cfg(not(feature = "no-usb"))]
            usb_driver,
            #[cfg(feature = "ble")]
            &stack,
            &mut storage,
            rmk_config,
        ),
        create_hid_report_interceptor(),
        user_controller.event_loop(),
        console_task
    ]
    .await;
}

async fn run_alloc_stats_reporter() {
    let mut psram_used_prev = 0;
    let mut heap_used_prev = 0;
    loop {
        let psram_stats = PSRAM_ALLOCATOR.stats();
        let heap_stats = esp_alloc::HEAP.stats();
        if psram_stats.current_usage != psram_used_prev {
            let difference = psram_stats.current_usage as isize - psram_used_prev as isize;
            psram_used_prev = psram_stats.current_usage;
            warn!(
                "PSRAM usage changed: {}{}\n{psram_stats}",
                if difference < 0 { '-' } else { '+' },
                difference.abs()
            );
        }
        if heap_stats.current_usage != heap_used_prev {
            let difference = heap_stats.current_usage as isize - heap_used_prev as isize;
            heap_used_prev = heap_stats.current_usage;
            warn!(
                "HEAP usage changed: {}{}\n{heap_stats}",
                if difference < 0 { '-' } else { '+' },
                difference.abs()
            );
        }
        Timer::after_secs(1).await;
    }
}

struct UserController {
    sub: ControllerSub,
}

impl UserController {
    fn new() -> Self {
        Self {
            sub: CONTROLLER_CHANNEL.subscriber().unwrap(),
        }
    }
}

impl Controller for UserController {
    type Event = ControllerEvent;

    async fn process_event(&mut self, event: Self::Event) {
        if let ControllerEvent::Key(keyboard_event, KeyAction::Single(Action::User(user_key_index))) =
            event
            && user_key_index == CustomKeycodes::FOCUS_LCD as u8
            && keyboard_event.pressed
        {
            let enabled = !LCD_ENABLED.fetch_xor(true, Ordering::SeqCst);

            match enabled {
                false => {
                    info!("Disabling LCD.");
                    *rmk::channel::KEYBOARD_REPORT_SENDER.write().await =
                        &rmk::channel::KEYBOARD_REPORT_RECEIVER;
                }
                true => {
                    info!("Enabling LCD.");
                    *rmk::channel::KEYBOARD_REPORT_SENDER.write().await = &KEYBOARD_REPORT_PROXY;
                }
            }
        }
    }

    async fn next_message(&mut self) -> Self::Event {
        self.sub.next_message_pure().await
    }
}

struct Framebuffer {
    width: u32,
    height: u32,
    dma_buf: Option<DmaTxBuf>,
}

impl Framebuffer {
    pub fn new(width: u32, height: u32) -> Self {
        let buffer_len = width as usize * height as usize * core::mem::size_of::<u16>();
        // Allocate the framebuffer in the external PSRAM memory.
        // Note: We just leak this buffer.
        let buffer_ptr = unsafe {
            // ⚠️ Note: For chips that support DMA to/from PSRAM (ESP32-S3) DMA transfers to/from PSRAM
            // have extra alignment requirements. The address and size of the buffer pointed to by each
            // descriptor must be a multiple of the cache line (block) size. This is 32 bytes on ESP32-S3.
            PSRAM_ALLOCATOR.alloc_caps(
                MemoryCapability::External.into(),
                Layout::from_size_align(buffer_len, 32).unwrap(),
            )
        };
        let buffer = unsafe { core::slice::from_raw_parts_mut(buffer_ptr, buffer_len) };
        let burst_config: BurstConfig = ExternalBurstConfig::Size16.into();

        info!(
            "PSRAM SPI burst config: max_compatible_chunk_size={}",
            burst_config.max_compatible_chunk_size()
        );
        let dma_buf_descs_len = esp_hal::dma::descriptor_count(
            buffer_len,
            burst_config.max_compatible_chunk_size(),
            false,
        );
        // Descriptors are initialized by `DmaTxBuf::new`.
        let dma_buf_descs =
            Box::leak(vec![DmaDescriptor::EMPTY; dma_buf_descs_len].into_boxed_slice());
        let dma_buf = DmaTxBuf::new(dma_buf_descs, buffer).unwrap();

        Self {
            width,
            height,
            dma_buf: Some(dma_buf),
        }
    }

    pub fn as_target_pixels(&mut self) -> &mut [Rgb565Pixel] {
        bytemuck::cast_slice_mut::<_, Rgb565Pixel>(self.dma_buf.as_mut().unwrap().as_mut_slice())
    }
}

#[embassy_executor::task]
async fn run_lcd_task(st7701s: St7701s<'static, Blocking>, framebuffer: &'static mut Framebuffer) {
    run_lcd(st7701s, framebuffer).await
}

async fn run_lcd(mut st7701s: St7701s<'static, Blocking>, framebuffer: &'static mut Framebuffer) {
    loop {
        // Timer::after(Duration::from_millis(100)).await;
        // yield_now().await;
        SIGNAL_LCD_SUBMIT.wait().await;

        // TODO: Use bounce buffers:
        // https://docs.espressif.com/projects/esp-idf/en/v5.0/esp32s3/api-reference/peripherals/lcd.html#bounce-buffer-with-single-psram-frame-buffer
        // This can be implemented as a `DmaTxBuffer`.
        let transfer = match st7701s.dpi.send(false, framebuffer.dma_buf.take().unwrap()) {
            Err((error, result_dpi, result_dma_buf)) => {
                error!(
                    "An error occurred while initiating transfer of the framebuffer to the LCD display: {error:?}"
                );
                st7701s.dpi = result_dpi;
                framebuffer.dma_buf = Some(result_dma_buf);
                continue;
            }
            Ok(transfer) => transfer,
        };

        // This could be used to allow other tasks to be executed on the first core, but that causes
        // the flash to be accessed, which interferes with the framebuffer transfer.
        // For that reason, it is disabled, and this task blocks the first core, until the transfer
        // is complete.
        #[cfg(not(feature = "limit-fps"))]
        while !transfer.is_done() {
            // Timer::after_millis(1).await;
            rmk::embassy_futures::yield_now().await;
        }

        let result;
        let dma_buf;
        (result, st7701s.dpi, dma_buf) = transfer.wait();
        framebuffer.dma_buf = Some(dma_buf);

        SIGNAL_UI_RENDER.signal(());

        if let Err(error) = result {
            error!(
                "An error occurred while transferring framebuffer to the LCD display: {error:?}"
            );
        }
    }
}

// // TODO: Not needed currently. If it is ever enabled, don't forget to register it in Io.
// #[handler]
// #[ram] // TODO: Is this necessary?
// fn interrupt_handler() {
//     // esp_println::println!(
//     //     "GPIO Interrupt with priority {}",
//     //     esp_hal::xtensa_lx::interrupt::get_level()
//     // );
// }