commit 6b672f840596b72b89cc45fdd7e8cc8ffb11e9b3
author milind-u <milind.upadhyay@gmail.com> Fri Feb 24 17:36:27 2023 -0800
committer milind-u <milind.upadhyay@gmail.com> Fri Feb 24 17:46:40 2023 -0800
tree 0e51067b30b88c5d97cb1e610635db89d04f52ba
parent d653aedc4e0bfc966e27f391eb7b1f3f03c1a4c2

Fix DMA pulse width reader

Didn't work with multiple readers because we were using the last sample
time, not the last time the reading went high.

Signed-off-by: milind-u <milind.upadhyay@gmail.com>
Change-Id: Ieedef0e8500f61d2881569bc7dfb56fbe843a97f

frc971/wpilib/dma_edge_counting.cc

diff --git a/frc971/wpilib/dma_edge_counting.cc b/frc971/wpilib/dma_edge_counting.cc
index ca2a10e..8864116 100644
--- a/frc971/wpilib/dma_edge_counting.cc
+++ b/frc971/wpilib/dma_edge_counting.cc
@@ -25,8 +25,12 @@
 }
 
 void DMAPulseWidthReader::UpdateFromSample(const DMASample &sample) {
-  if (have_prev_sample_ && prev_sample_.Get(input_) && !sample.Get(input_)) {
-    last_width_ = sample.GetTimestamp() - prev_sample_.GetTimestamp();
+  if (have_prev_sample_ && high_time_ != 0 && prev_sample_.Get(input_) &&
+      !sample.Get(input_)) {
+    last_width_ = (sample.GetTime() - high_time_) * 0.000001;
+  } else if (have_prev_sample_ && !prev_sample_.Get(input_) &&
+             sample.Get(input_)) {
+    high_time_ = prev_sample_.GetTime();
   }
   have_prev_sample_ = true;
   prev_sample_ = sample;

frc971/wpilib/dma_edge_counting.h

diff --git a/frc971/wpilib/dma_edge_counting.h b/frc971/wpilib/dma_edge_counting.h
index 2d49ecb..a945909 100644
--- a/frc971/wpilib/dma_edge_counting.h
+++ b/frc971/wpilib/dma_edge_counting.h
@@ -5,15 +5,13 @@
 #include <optional>
 #include <vector>
 
-#include "aos/macros.h"
-
 #include "aos/containers/sized_array.h"
-#include "frc971/wpilib/ahal/Utility.h"
-#include "frc971/wpilib/dma.h"
-
+#include "aos/macros.h"
 #include "frc971/wpilib/ahal/AnalogInput.h"
 #include "frc971/wpilib/ahal/DigitalInput.h"
 #include "frc971/wpilib/ahal/Encoder.h"
+#include "frc971/wpilib/ahal/Utility.h"
+#include "frc971/wpilib/dma.h"
 #undef ERROR
 
 namespace frc971 {
@@ -47,6 +45,7 @@
 
   void set_input(frc::DigitalInput *input) { input_ = input; }
 
+  // Last pulse width in seconds
   double last_width() const { return last_width_; }
 
  private:
@@ -65,6 +64,8 @@
   DMASample prev_sample_;
   // Whether or not we actually have anything in prev_sample_.
   bool have_prev_sample_ = false;
+  // Last time the reading switched to high
+  uint64_t high_time_ = 0;
 
   double last_width_ = ::std::numeric_limits<double>::quiet_NaN();