sram1_test.rs

#![no_main]
#![no_std]

use core::mem::MaybeUninit;
use cortex_m_rt::entry;
use hal::{
    pwr::PwrExt,
    rcc::RccExt,
};
use panic_rtt_target as _;
use rtt_target::rprintln;
use stm32h7xx_hal::{self as hal, pac, prelude::*};

#[repr(C, packed)]
#[derive(Debug, Clone, Copy)]
struct LedState {
    on: u16,
    off: u16,
}

#[repr(C, packed)]
#[derive(Debug, Clone, Copy)]
struct LedArray {
    reg_addr: u8,
    leds: [LedState; 16],
}

#[link_section = ".sram1"]
static mut LED_ARRAY: MaybeUninit<LedArray> = MaybeUninit::uninit();

unsafe fn any_as_u8_slice<T: Sized>(p: &T) -> &[u8] {
    core::slice::from_raw_parts((p as *const T) as *const u8, core::mem::size_of::<T>())
}

#[entry]
fn main() -> ! {
    rtt_target::rtt_init_print!();

    let _cp = cortex_m::Peripherals::take().unwrap();
    let dp = pac::Peripherals::take().unwrap();

    let pwr = dp.PWR.constrain();
    // set to Vcore = maximum freq, vos0
    let pwrcfg = pwr.vos0(&dp.SYSCFG).freeze();
    let rcc = dp.RCC.constrain();

    // 480MHz system clock
    let _ccdr = rcc
        .use_hse(16.mhz())
        .sys_ck(480.mhz())
        .pll1_strategy(hal::rcc::PllConfigStrategy::Iterative)
        .pll1_p_ck(480.mhz()) // 480 MHz
        .pll1_q_ck(160.mhz()) // 160 MHz
        .pll1_r_ck(320.mhz()) // 320 MHz
        .pll3_strategy(hal::rcc::PllConfigStrategy::Iterative)
        .pll3_p_ck(49_166_667.hz())
        .pll3_q_ck(157_333_334.hz())
        .pll3_r_ck(24_583_334.hz())
        .freeze(pwrcfg, &dp.SYSCFG);

    rprintln!("sizeof LedArray is {}", core::mem::size_of::<LedArray>());

    // initialize LED_ARRAY
    unsafe {
        LED_ARRAY.as_mut_ptr().write(LedArray {
            reg_addr: 0x06,
            leds: [
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0xfff },
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0x100 },
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0 },
                LedState { on: 0, off: 0xfff },
                LedState { on: 0, off: 0 },
            ],
        });
    }

    let led_array = unsafe { &*LED_ARRAY.as_ptr() };

    // rprintln!("reg_addr = {}", led_array.reg_addr);
    // rprintln!("leds[0].on = {}", {led_array.leds[0].on});
    // rprintln!("leds[15].off = {}", {led_array.leds[15].off});

    let led_bytes: &[u8] = unsafe { any_as_u8_slice(led_array) };
    for (idx, b) in led_bytes.iter().enumerate() {
        rprintln!("{}: {:02x}", idx, b);
    }

    loop {}
}