STM32 Timer + Rust: Reading 1 GPIO Pin Using 2 Channels

  1#![no_std]
  2#![no_main]
  3
  4use core::sync::atomic::{AtomicU32, Ordering};
  5
  6use defmt_rtt as _;
  7use panic_probe as _;
  8
  9use cortex_m_rt::entry;
 10use stm32f1xx_hal::{
 11    flash::FlashExt,
 12    pac::{self, interrupt},
 13    prelude::*,
 14    rcc::{Config, RccExt},
 15    time::Hertz,
 16    timer::{Event, Timer},
 17};
 18
 19static NUMB_OVERFLOW: AtomicU32 = AtomicU32::new(0);
 20
 21#[entry]
 22fn main() -> ! {
 23    defmt::println!("STM32F103C8 Timer Channel Cross Mapping");
 24
 25    let dp = pac::Peripherals::take().unwrap();
 26
 27    let mut flash = dp.FLASH.constrain();
 28
 29    let rcc = dp.RCC.constrain();
 30
 31    let clock_config = Config::default()
 32        .use_hse(Hertz::MHz(8))
 33        .sysclk(Hertz::MHz(72))
 34        .hclk(Hertz::MHz(72))
 35        .pclk1(Hertz::MHz(36));
 36
 37    let mut clocks = rcc.freeze(clock_config, &mut flash.acr);
 38
 39    let mut gpioa = dp.GPIOA.split(&mut clocks);
 40
 41    let channel_1 = gpioa.pa0.into_pull_down_input(&mut gpioa.crl);
 42
 43    let timer2 = Timer::new(dp.TIM2, &mut clocks);
 44
 45    unsafe {
 46        pac::NVIC::unmask(interrupt::TIM2);
 47    }
 48
 49    let mut counter = timer2.counter_hz();
 50
 51    counter.listen(Event::Update);
 52
 53    let timer_register = unsafe { &*pac::TIM2::ptr() };
 54
 55    timer_register.ccmr1_input().modify(|_, w| w.cc1s().ti1());
 56    timer_register.ccmr1_input().modify(|_, w| w.cc2s().ti1());
 57
 58    timer_register
 59        .ccmr1_input()
 60        .modify(|_, w| w.ic1f().fck_int_n8());
 61    timer_register
 62        .ccmr1_input()
 63        .modify(|_, w| w.ic2f().fck_int_n8());
 64
 65    timer_register.ccer().modify(|_, w| w.cc1e().set_bit());
 66    timer_register.ccer().modify(|_, w| w.cc2e().set_bit());
 67
 68    timer_register.ccer().modify(|_, w| w.cc1p().clear_bit());
 69    timer_register.ccer().modify(|_, w| w.cc2p().set_bit());
 70
 71    counter.start_raw(7199, 65535);
 72
 73    let mut start_press_tick = 0u16;
 74
 75    let mut is_pressed = false;
 76
 77    loop {
 78        if counter.get_interrupt().contains(Event::C1) {
 79            let captured_tick = timer_register.ccr1().read().ccr().bits() as u16;
 80
 81            let pin_is_high = channel_1.is_high();
 82
 83            if pin_is_high && !is_pressed {
 84                start_press_tick = captured_tick;
 85                NUMB_OVERFLOW.store(0, Ordering::SeqCst);
 86
 87                is_pressed = true;
 88                defmt::println!("--- Button Pressed ---");
 89                defmt::println!("start: {}", start_press_tick);
 90            }
 91            counter.clear_interrupt(Event::C1);
 92        }
 93
 94        if counter.get_interrupt().contains(Event::C2) {
 95            let captured_tick = timer_register.ccr2().read().ccr().bits() as u16;
 96
 97            let pin_is_high = channel_1.is_high();
 98            if !pin_is_high && is_pressed {
 99                let total_overflow = NUMB_OVERFLOW.load(Ordering::SeqCst);
100
101                let total_tick =
102                    (total_overflow * 65536) + captured_tick as u32 - start_press_tick as u32;
103
104                defmt::println!(
105                    "end: {} | total_overflow: {}",
106                    captured_tick,
107                    total_overflow
108                );
109                defmt::println!("press long: {} ms", total_tick as f32 / 10f32);
110                defmt::println!("----------------------");
111                is_pressed = false;
112            }
113
114            counter.clear_interrupt(Event::C2);
115        }
116    }
117}
118
119#[interrupt]
120fn TIM2() {
121    let timer_register = unsafe { &*pac::TIM2::ptr() };
122
123    // check update interrupt flag
124    if timer_register.sr().read().uif().bit_is_set() {
125        // Increment overflow count
126        NUMB_OVERFLOW.fetch_add(1, Ordering::SeqCst);
127        // Clear update interrupt flag
128        timer_register.sr().modify(|_, w| w.uif().clear_bit());
129    }
130}