Struct CYCCNTClock

pub struct CYCCNTClock<const SYSCLK_HZ: u32> {}

Clock based on the Cortex-M CYCCNT counter allowing to measure time durations and produce delays.
Precise at a microsecond scale if your SYSCLK clock is greater than 1MHz

Implementations

impl<const SYSCLK_HZ: u32> CYCCNTClock<SYSCLK_HZ>

pub fn now() -> Instant<SYSCLK_HZ>

Return an Instant object corresponding to a snapshot created at the time this method was called. Panic if the counter has not been initialized with CYCCNTClock::init() before.

   const SYSCLK_FREQ_HZ : u32 = 8_000_000;
   let t1 = CYCCNTClock<SYSCLK_FREQ_HZ>::now();
     
   // Wait 100 us
   let duration = Duration::micros(100);
   CYCCNTClock<SYSCLK_FREQ_HZ>::delay(duration)
    
   let t2 = CYCCNTClock<SYSCLK_FREQ_HZ>::now();
   let elpased_time = t2 - t1; // Very small elapsed time
   println!("time_us {}", elapsed_time.to_micros());

pub fn delay(duration: Duration<SYSCLK_HZ>)

Blocking wait for the duration specified as argument Interrupts can still trigger during this call. Panic if the counter has not been initialized with CYCCNTClock::init() before.

   const SYSCLK_FREQ_HZ : u32 = 8_000_000;
   let t1 = CYCCNTClock<SYSCLK_FREQ_HZ>::now();
     
   // Wait 100 us
   let duration = Duration::micros(100);
   CYCCNTClock<SYSCLK_FREQ_HZ>::delay(duration)
    
   let t2 = CYCCNTClock<SYSCLK_FREQ_HZ>::now();
   let elpased_time = t2 - t1; // Very small elapsed time
   println!("time_us {}", elapsed_time.to_micros());

pub fn update()

Synchronize the hardware counter with this clock. Must be called at least one time for every CYCCNT counter cycle after init. Otherwise time counting will be corrupted. In general, calling this method in every SysTick IRQ call is the simpler option This method will NOT panic if the CYCCNTClock::init() method has not be called first.

pub fn init(dcb: &mut DCB, dwt: DWT)

Enable CYCCNT counting capability of the cortex core and start the couting

 let mut cp = cortex_m::Peripherals::take().unwrap();
 let mut dcb = cp.DCB;
 let dwt = cp.DWT;
 CYCCNTClock<SYSCLK_FREQ_HZ>::init(&mut dcb, dwt);