commit a2e612b28294352fe8ccbaaef7bb6bfb54b6899c
author milind-u <milind.upadhyay@gmail.com> Fri Feb 24 18:00:59 2023 -0800
committer milind-u <milind.upadhyay@gmail.com> Fri Feb 24 19:27:05 2023 -0800
tree e0f0e204967ef270544197887e02ca0335e52cf1
parent 6b672f840596b72b89cc45fdd7e8cc8ffb11e9b3

Reset DMA pulse width reader state when stale

We should always be updating at a regular interval.

Signed-off-by: milind-u <milind.upadhyay@gmail.com>
Change-Id: Ibf3071831eb42123697b4f47f1b8056557ea42ee

frc971/wpilib/dma_edge_counting.cc

diff --git a/frc971/wpilib/dma_edge_counting.cc b/frc971/wpilib/dma_edge_counting.cc
index 8864116..ba8fdf4 100644
--- a/frc971/wpilib/dma_edge_counting.cc
+++ b/frc971/wpilib/dma_edge_counting.cc
@@ -27,15 +27,29 @@
 void DMAPulseWidthReader::UpdateFromSample(const DMASample &sample) {
   if (have_prev_sample_ && high_time_ != 0 && prev_sample_.Get(input_) &&
       !sample.Get(input_)) {
-    last_width_ = (sample.GetTime() - high_time_) * 0.000001;
+    last_width_ = (sample.GetTime() - high_time_) * 1e-6;
+    high_time_ = 0;
+    poll_count_ = 0;
   } else if (have_prev_sample_ && !prev_sample_.Get(input_) &&
              sample.Get(input_)) {
     high_time_ = prev_sample_.GetTime();
+    poll_count_ = 0;
   }
   have_prev_sample_ = true;
   prev_sample_ = sample;
 }
 
+void DMAPulseWidthReader::UpdatePolledValue() {
+  // If we are polled without an update for too long, reset
+  constexpr size_t kMaxPollCount = 4;
+  if (poll_count_ > kMaxPollCount) {
+    high_time_ = 0;
+    have_prev_sample_ = false;
+    last_width_ = ::std::numeric_limits<double>::quiet_NaN();
+  }
+  poll_count_++;
+}
+
 void DMAPulseSeparationReader::UpdateFromSample(const DMASample &sample) {
   // save the time of the falling edge of the input one
   if (have_prev_sample_ && !sample.Get(input_one_) &&

frc971/wpilib/dma_edge_counting.h

diff --git a/frc971/wpilib/dma_edge_counting.h b/frc971/wpilib/dma_edge_counting.h
index a945909..4d1246c 100644
--- a/frc971/wpilib/dma_edge_counting.h
+++ b/frc971/wpilib/dma_edge_counting.h
@@ -50,7 +50,7 @@
 
  private:
   void UpdateFromSample(const DMASample & /*sample*/) override;
-  void UpdatePolledValue() override {}
+  void UpdatePolledValue() override;
 
   void PollFromSample(const DMASample & /*sample*/) override {}
   void AddToDMA(DMA *dma) override {
@@ -66,6 +66,8 @@
   bool have_prev_sample_ = false;
   // Last time the reading switched to high
   uint64_t high_time_ = 0;
+  // Number of times we've been polled without an update
+  size_t poll_count_ = 0;
 
   double last_width_ = ::std::numeric_limits<double>::quiet_NaN();