timestamping: docs and naming

src/bin/lockin-external.rs

@@ -117,14 +117,14 @@ const APP: () = {
         let iir_state = c.resources.iir_state;
         let lockin = c.resources.lockin;
 
-        let t = c
+        let timestamp = c
             .resources
             .timestamper
             .latest_timestamp()
             .unwrap_or_else(|t| t) // Ignore timer capture overflows.
             .map(|t| t as i32);
         let (pll_phase, pll_frequency) = c.resources.pll.update(
-            t,
+            timestamp,
             22, // frequency settling time (log2 counter cycles), TODO: expose
             22, // phase settling time, TODO: expose
         );

src/hardware/configuration.rs

@@ -211,12 +211,11 @@ pub fn setup(
         // Configure the timer to count at the designed tick rate. We will manually set the
         // period below.
         timer5.pause();
-        timer5.reset_counter();
         timer5.set_tick_freq(design_parameters::TIMER_FREQUENCY);
 
-        // The timestamp timer must run at exactly a multiple of the sample timer based on the
+        // The timestamp timer runs at the counter cycle period as the sampling timers.
-        // batch size. To accomodate this, we manually set the prescaler identical to the sample
+        // To accomodate this, we manually set the prescaler identical to the sample
-        // timer, but use a period that is longer.
+        // timer, but use maximum overflow period.
         let mut timer = timers::TimestampTimer::new(timer5);
 
         timer.set_period_ticks(u32::MAX);