diff options
| -rwxr-xr-x | src/bin/luchie.rs | 54 |
1 files changed, 37 insertions, 17 deletions
diff --git a/src/bin/luchie.rs b/src/bin/luchie.rs index be89fa7..5279f95 100755 --- a/src/bin/luchie.rs +++ b/src/bin/luchie.rs @@ -29,6 +29,40 @@ use usbd_human_interface_device::{ }; use usbd_serial::{SerialPort, USB_CLASS_CDC}; +// Relies on cortex-m +struct SysTimer { + syst: pac::SYST, + last: u32, + err: u32, + reload: u32, + ticks_per_microsec: u32, +} + +impl SysTimer { + pub fn new(mut syst: pac::SYST, ticks_per_microsec: u32) -> Self { + syst.set_clock_source(cortex_m::peripheral::syst::SystClkSource::Core); + let reload = 0xffffff; + syst.set_reload(reload); + syst.clear_current(); + syst.enable_counter(); + + Self { syst, last: 0, err: 0, reload, ticks_per_microsec } + } + + pub fn update(&mut self) -> u32 { + let mut time = self.reload - cortex_m::peripheral::SYST::get_current(); + if self.syst.has_wrapped() { + time += self.reload + 1; + } + let elapsed = time.wrapping_sub(self.last) + self.err; + self.err = elapsed % self.ticks_per_microsec; + let elapsed = elapsed / self.ticks_per_microsec; + self.last = time & self.reload; // FIXME: might not be 2^x - 1 + + elapsed + } +} + #[entry] fn main() -> ! { let cp = cortex_m::Peripherals::take().unwrap(); @@ -69,12 +103,7 @@ fn main() -> ! { logln!("🐁 luchie starting…"); logln!("⏲️ init timer"); - let mut syst = cp.SYST; - syst.set_clock_source(cortex_m::peripheral::syst::SystClkSource::Core); - let syst_reload = 0xffffff; - syst.set_reload(syst_reload); - syst.clear_current(); - syst.enable_counter(); + let mut sys_timer = SysTimer::new(cp.SYST, clocks.sysclk().to_MHz()); // cirque spi connections to spi1: // @@ -150,18 +179,9 @@ fn main() -> ! { let mut abs_to_rel = AbsToRel::new(); let mut trackball = TrackBall::new(1); - let ticks_per_microsec = clocks.sysclk().to_MHz(); - let mut last_time = 0; - let mut time_error = 0; loop { - let mut time = syst_reload - cortex_m::peripheral::SYST::get_current(); - if syst.has_wrapped() { - time += syst_reload + 1; - } - let elapsed = time.wrapping_sub(last_time) + time_error; - time_error = elapsed % ticks_per_microsec; - let elapsed = elapsed / ticks_per_microsec; - last_time = time & syst_reload; + let elapsed = sys_timer.update(); + usb_dev.poll(&mut [&mut serial, &mut mouse]); let mut buf = [0u8; 64]; |