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-rwxr-xr-xsrc/bin/luchie.rs54
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];