Tweak RTC timer a bit.

This seems to get it closer to what the Arduino thinks is a
millisecond. Measured by dumping timestamps on the Arduino with Linux
timestamps. There is a fair amount of variance in the Arduino's serial
output timing, but this is also close to what Linux thinks is ok.

It's still slow by about ~5%, but I'm not sure how to correct it
better, or if it's even worth bothering since everything is so
imprecise anyway.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/rtc.rs b/src/rtc.rs
index 79e450a..fa7b347 100644
--- a/src/rtc.rs
+++ b/src/rtc.rs
@@ -21,8 +21,9 @@ impl Clock {
 
 static CLOCK: Clock = Clock::new();
 
-// Set to run every ~500µs.
-static COUNTER: u32 = 16; // 32 ticks requires 1024 cycles at 32,768Hz for 1 second.
+// Set to run every ~500µs. This has been loosely calibrated from a
+// nrf52 clock running Arduino and a Linux host.
+static COUNTER: u32 = 13;
 
 pub fn setup(mut rtc: RTC, clocks: &mut GenericClockController) -> impl FnMut() {
     let rtc_clock = &clocks.gclk1();