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| 1 | +//! Delay implementation based on general-purpose 32 bit timers and System timer (SysTick). |
| 2 | +//! |
| 3 | +//! TIM2 and TIM5 are a general purpose 32-bit auto-reload up/downcounter with |
| 4 | +//! a 16-bit prescaler. |
| 5 | +
|
| 6 | +use cast::{u16, u32}; |
| 7 | +use cortex_m::peripheral::SYST; |
| 8 | +use embedded_hal::blocking::delay::{DelayMs, DelayUs}; |
| 9 | + |
| 10 | +use super::{Delay, Wait}; |
| 11 | + |
| 12 | +impl DelayUs<u32> for Delay<SYST> { |
| 13 | + fn delay_us(&mut self, us: u32) { |
| 14 | + // The SysTick Reload Value register supports values between 1 and 0x00FFFFFF. |
| 15 | + const MAX_RVR: u32 = 0x00FF_FFFF; |
| 16 | + |
| 17 | + let mut total_rvr = us * (self.clk.0 / 8_000_000); |
| 18 | + |
| 19 | + while total_rvr != 0 { |
| 20 | + let current_rvr = if total_rvr <= MAX_RVR { |
| 21 | + total_rvr |
| 22 | + } else { |
| 23 | + MAX_RVR |
| 24 | + }; |
| 25 | + |
| 26 | + self.tim.set_reload(current_rvr); |
| 27 | + self.tim.clear_current(); |
| 28 | + self.tim.enable_counter(); |
| 29 | + |
| 30 | + // Update the tracking variable while we are waiting... |
| 31 | + total_rvr -= current_rvr; |
| 32 | + |
| 33 | + while !self.tim.has_wrapped() {} |
| 34 | + |
| 35 | + self.tim.disable_counter(); |
| 36 | + } |
| 37 | + } |
| 38 | +} |
| 39 | + |
| 40 | +impl DelayMs<u32> for Delay<SYST> { |
| 41 | + fn delay_ms(&mut self, ms: u32) { |
| 42 | + self.delay_us(ms * 1_000); |
| 43 | + } |
| 44 | +} |
| 45 | + |
| 46 | +impl DelayUs<u16> for Delay<SYST> { |
| 47 | + fn delay_us(&mut self, us: u16) { |
| 48 | + self.delay_us(u32(us)) |
| 49 | + } |
| 50 | +} |
| 51 | + |
| 52 | +impl DelayMs<u16> for Delay<SYST> { |
| 53 | + fn delay_ms(&mut self, ms: u16) { |
| 54 | + self.delay_ms(u32(ms)); |
| 55 | + } |
| 56 | +} |
| 57 | + |
| 58 | +impl DelayUs<u8> for Delay<SYST> { |
| 59 | + fn delay_us(&mut self, us: u8) { |
| 60 | + self.delay_us(u32(us)) |
| 61 | + } |
| 62 | +} |
| 63 | + |
| 64 | +impl DelayMs<u8> for Delay<SYST> { |
| 65 | + fn delay_ms(&mut self, ms: u8) { |
| 66 | + self.delay_ms(u32(ms)); |
| 67 | + } |
| 68 | +} |
| 69 | + |
| 70 | +impl<TIM> DelayUs<u32> for Delay<TIM> |
| 71 | +where |
| 72 | + Self: Wait, |
| 73 | +{ |
| 74 | + /// Sleep for up to 2^32-1 microseconds (~71 minutes). |
| 75 | + fn delay_us(&mut self, us: u32) { |
| 76 | + // Set up prescaler so that a tick takes exactly 1 µs. |
| 77 | + // |
| 78 | + // For example, if the clock is set to 48 MHz, with a prescaler of 48 |
| 79 | + // we'll get ticks that are 1 µs long. This means that we can write the |
| 80 | + // delay value directly to the auto-reload register (ARR). |
| 81 | + let psc = u16(self.clk.0 / 1_000_000).expect("Prescaler does not fit in u16"); |
| 82 | + let arr = us; |
| 83 | + self.wait(psc, arr); |
| 84 | + } |
| 85 | +} |
| 86 | + |
| 87 | +impl<TIM> DelayMs<u32> for Delay<TIM> |
| 88 | +where |
| 89 | + Self: Wait, |
| 90 | +{ |
| 91 | + /// Sleep for up to (2^32)/2-1 milliseconds (~24 days). |
| 92 | + /// If the `ms` value is larger than 2147483647, the code will panic. |
| 93 | + fn delay_ms(&mut self, ms: u32) { |
| 94 | + // See next section for explanation why the usable range is reduced. |
| 95 | + assert!(ms <= 2_147_483_647); // (2^32)/2-1 |
| 96 | + |
| 97 | + // Set up prescaler so that a tick takes exactly 0.5 ms. |
| 98 | + // |
| 99 | + // For example, if the clock is set to 48 MHz, with a prescaler of 24'000 |
| 100 | + // we'll get ticks that are 0.5 ms long. This means that we can write the |
| 101 | + // delay value multipled by two to the auto-reload register (ARR). |
| 102 | + // |
| 103 | + // Note that we cannot simply use a prescaler value where the tick corresponds |
| 104 | + // to 1 ms, because then a clock of 100 MHz would correspond to a prescaler |
| 105 | + // value of 100'000, which doesn't fit in the 16-bit PSC register. |
| 106 | + // |
| 107 | + // Unfortunately this means that only one half of the full 32-bit range |
| 108 | + // can be used, but 24 days should be plenty of usable delay time. |
| 109 | + let psc = u16(self.clk.0 / 1000 / 2).expect("Prescaler does not fit in u16"); |
| 110 | + |
| 111 | + // Since PSC = 0.5 ms, double the value for the ARR |
| 112 | + let arr = ms << 1; |
| 113 | + |
| 114 | + self.wait(psc, arr); |
| 115 | + } |
| 116 | +} |
| 117 | + |
| 118 | +impl<TIM> DelayUs<u16> for Delay<TIM> |
| 119 | +where |
| 120 | + Self: Wait, |
| 121 | +{ |
| 122 | + /// Sleep for up to 2^16-1 microseconds (~65 milliseconds). |
| 123 | + fn delay_us(&mut self, us: u16) { |
| 124 | + // See DelayUs<u32> for explanations. |
| 125 | + let psc = u16(self.clk.0 / 1_000_000).expect("Prescaler does not fit in u16"); |
| 126 | + let arr = u32(us); |
| 127 | + self.wait(psc, arr); |
| 128 | + } |
| 129 | +} |
| 130 | + |
| 131 | +impl<TIM> DelayMs<u16> for Delay<TIM> |
| 132 | +where |
| 133 | + Self: Wait, |
| 134 | +{ |
| 135 | + /// Sleep for up to (2^16)-1 milliseconds (~65 seconds). |
| 136 | + fn delay_ms(&mut self, ms: u16) { |
| 137 | + // See DelayMs<u32> for explanations. Since the value range is only 16 bit, |
| 138 | + // we don't need an assert here. |
| 139 | + let psc = u16(self.clk.0 / 1000 / 2).expect("Prescaler does not fit in u16"); |
| 140 | + let arr = u32(ms) << 1; |
| 141 | + self.wait(psc, arr); |
| 142 | + } |
| 143 | +} |
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