More updates after PR review

src/design_parameters.rs

@@ -9,3 +9,18 @@ pub const ADC_DAC_SCK_MAX: MegaHertz = MegaHertz(50);
 
 /// The optimal counting frequency of the hardware timers used for timestamping and sampling.
 pub const TIMER_FREQUENCY: MegaHertz = MegaHertz(100);
+
+/// The QSPI frequency for communicating with the pounder DDS.
+pub const POUNDER_QSPI_FREQUENCY: MegaHertz = MegaHertz(40);
+
+/// The delay after initiating a QSPI transfer before asserting the IO_Update for the pounder DDS.
+// Pounder Profile writes are always 16 bytes, with 2 cycles required per byte, coming out to a
+// total of 32 QSPI clock cycles. The QSPI is configured for 40MHz, so this comes out to an offset
+// of 800nS. We use 900ns to be safe.
+pub const POUNDER_IO_UPDATE_DELAY: f32 = 900_e-9;
+
+/// The duration to assert IO_Update for the pounder DDS.
+// IO_Update should be latched for 4 SYNC_CLK cycles after the QSPI profile write. With pounder
+// SYNC_CLK running at 100MHz (1/4 of the pounder reference clock of 400MHz), this corresponds to
+// 40ns. To accomodate rounding errors, we use 50ns instead.
+pub const POUNDER_IO_UPDATE_DURATION: f32 = 50_e-9;

src/digital_input_stamper.rs

@@ -24,7 +24,7 @@
 ///!
 ///! This module only supports DI0 for timestamping due to trigger constraints on the DIx pins. If
 ///! timestamping is desired in DI1, a separate timer + capture channel will be necessary.
-use super::{hal, timers, SAMPLE_BUFFER_SIZE, ADC_SAMPLE_TICKS};
+use super::{hal, timers, ADC_SAMPLE_TICKS, SAMPLE_BUFFER_SIZE};
 
 /// Calculate the period of the digital input timestampe timer.
 ///
@@ -39,7 +39,8 @@ use super::{hal, timers, SAMPLE_BUFFER_SIZE, ADC_SAMPLE_TICKS};
 /// A 32-bit value that can be programmed into a hardware timer period register.
 pub fn calculate_timestamp_timer_period() -> u32 {
     // Calculate how long a single batch requires in timer ticks.
-    let batch_duration_ticks: u64 = SAMPLE_BUFFER_SIZE as u64 * ADC_SAMPLE_TICKS as u64;
+    let batch_duration_ticks: u64 =
+        SAMPLE_BUFFER_SIZE as u64 * ADC_SAMPLE_TICKS as u64;
 
     // Calculate the largest power-of-two that is less than or equal to
     // `batches_per_overflow`.  This is completed by eliminating the least significant
@@ -101,10 +102,8 @@ impl InputStamper {
     /// To prevent timestamp loss, the batch size and sampling rate must be adjusted such that at
     /// most one timestamp will occur in each data processing cycle.
     pub fn latest_timestamp(&mut self) -> Option<u32> {
-        if self.capture_channel.check_overcapture() {
+        self.capture_channel
-            panic!("DI0 timestamp overrun");
+            .latest_capture()
-        }
+            .expect("DI0 timestamp overrun")
-
-        self.capture_channel.latest_capture()
     }
 }

src/main.rs

@@ -318,7 +318,8 @@ const APP: () = {
             // timer, but use a period that is longer.
             let mut timer = timers::TimestampTimer::new(timer5);
 
-            let period = digital_input_stamper::calculate_timestamp_timer_period();
+            let period =
+                digital_input_stamper::calculate_timestamp_timer_period();
             timer.set_period_ticks(period);
 
             timer
@@ -543,7 +544,7 @@ const APP: () = {
                     let qspi = hal::qspi::Qspi::bank2(
                         dp.QUADSPI,
                         qspi_pins,
-                        40.mhz(),
+                        design_parameters::POUNDER_QSPI_FREQUENCY,
                         &ccdr.clocks,
                         ccdr.peripheral.QSPI,
                     );
@@ -665,30 +666,26 @@ const APP: () = {
                         ccdr.peripheral.HRTIM,
                     );
 
-                    // IO_Update should be latched for 4 SYNC_CLK cycles after the QSPI profile
+                    // IO_Update occurs after a fixed delay from the QSPI write. Note that the timer
-                    // write. With pounder SYNC_CLK running at 100MHz (1/4 of the pounder reference
+                    // is triggered after the QSPI write, which can take approximately 120nS, so
-                    // clock of 400MHz), this corresponds to 40ns. To accomodate rounding errors, we
+                    // there is additional margin.
-                    // use 50ns instead.
-                    //
-                    // Profile writes are always 16 bytes, with 2 cycles required per byte, coming
-                    // out to a total of 32 QSPI clock cycles. The QSPI is configured for 40MHz, so
-                    // this comes out to an offset of 800nS. We use 900ns to be safe - note that the
-                    // timer is triggered after the QSPI write, which can take approximately 120nS,
-                    // so there is additional margin.
                     hrtimer.configure_single_shot(
                         hrtimer::Channel::Two,
-                        50_e-9,
+                        design_parameters::POUNDER_IO_UPDATE_DURATION,
-                        900_e-9,
+                        design_parameters::POUNDER_IO_UPDATE_DELAY,
                     );
 
                     // Ensure that we have enough time for an IO-update every sample.
-                    let sample_frequency =
+                    let sample_frequency = (design_parameters::TIMER_FREQUENCY.0
-                        (design_parameters::TIMER_FREQUENCY.0 as f32
+                        as f32
-                            * 1_000_000.0)
+                        * 1_000_000.0)
-                            / ADC_SAMPLE_TICKS as f32;
+                        / ADC_SAMPLE_TICKS as f32;
 
                     let sample_period = 1.0 / sample_frequency;
-                    assert!(sample_period > 900_e-9);
+                    assert!(
+                        sample_period
+                            > design_parameters::POUNDER_IO_UPDATE_DELAY
+                    );
 
                     hrtimer
                 };

src/timers.rs

@@ -147,17 +147,25 @@ macro_rules! timer_channels {
             impl [< Channel $index InputCapture >] {
                 /// Get the latest capture from the channel.
                 #[allow(dead_code)]
-                pub fn latest_capture(&mut self) -> Option<u32> {
+                pub fn latest_capture(&mut self) -> Result<Option<u32>, ()> {
                     // Note(unsafe): This channel owns all access to the specific timer channel.
                     // Only atomic operations on completed on the timer registers.
                     let regs = unsafe { &*<$TY>::ptr() };
                     let sr = regs.sr.read();
                     let ccx = regs.[< ccr $index >].read();
-                    if sr.[< cc $index if >]().bit_is_set() {
+
+                    let result = if sr.[< cc $index if >]().bit_is_set() {
                         regs.sr.modify(|_, w| w.[< cc $index if >]().clear_bit());
                         Some(ccx.ccr().bits())
                     } else {
                         None
+                    };
+
+                    // If there is an overcapture, return an error.
+                    if sr.[< cc $index of >]().bit_is_clear() {
+                        Ok(result)
+                    } else {
+                        Err(())
                     }
                 }