SensorReader PWM Refactor.
Refactored the pwm trigger and pwm detecter out of the year specific.
Change-Id: Ie89332fe6e1bcc0f465b742055ec4cf392a20c7e
diff --git a/frc971/wpilib/sensor_reader.cc b/frc971/wpilib/sensor_reader.cc
new file mode 100644
index 0000000..f2123a1
--- /dev/null
+++ b/frc971/wpilib/sensor_reader.cc
@@ -0,0 +1,87 @@
+#include "frc971/wpilib/sensor_reader.h"
+
+#include "aos/init.h"
+#include "aos/util/compiler_memory_barrier.h"
+#include "frc971/wpilib/ahal/DigitalInput.h"
+#include "frc971/wpilib/ahal/Utility.h"
+
+namespace frc971 {
+namespace wpilib {
+
+SensorReader::SensorReader() {}
+
+void SensorReader::set_pwm_trigger(
+ ::std::unique_ptr<frc::DigitalInput> pwm_trigger) {
+ medium_encoder_filter_.Add(pwm_trigger.get());
+ pwm_trigger_ = ::std::move(pwm_trigger);
+}
+
+void SensorReader::RunPWMDetecter() {
+ ::aos::SetCurrentThreadRealtimePriority(41);
+
+ pwm_trigger_->RequestInterrupts();
+ // Rising edge only.
+ pwm_trigger_->SetUpSourceEdge(true, false);
+
+ monotonic_clock::time_point last_posedge_monotonic =
+ monotonic_clock::min_time;
+
+ while (run_) {
+ auto ret = pwm_trigger_->WaitForInterrupt(1.0, true);
+ if (ret == frc::InterruptableSensorBase::WaitResult::kRisingEdge) {
+ // Grab all the clocks.
+ const double pwm_fpga_time = pwm_trigger_->ReadRisingTimestamp();
+
+ aos_compiler_memory_barrier();
+ const double fpga_time_before = frc::GetFPGATime() * 1e-6;
+ aos_compiler_memory_barrier();
+ const monotonic_clock::time_point monotonic_now = monotonic_clock::now();
+ aos_compiler_memory_barrier();
+ const double fpga_time_after = frc::GetFPGATime() * 1e-6;
+ aos_compiler_memory_barrier();
+
+ const double fpga_offset =
+ (fpga_time_after + fpga_time_before) / 2.0 - pwm_fpga_time;
+
+ // Compute when the edge was.
+ const monotonic_clock::time_point monotonic_edge =
+ monotonic_now - chrono::duration_cast<chrono::nanoseconds>(
+ chrono::duration<double>(fpga_offset));
+
+ LOG(DEBUG, "Got PWM pulse %f spread, %f offset, %lld trigger\n",
+ fpga_time_after - fpga_time_before, fpga_offset,
+ monotonic_edge.time_since_epoch().count());
+
+ // Compute bounds on the timestep and sampling times.
+ const double fpga_sample_length = fpga_time_after - fpga_time_before;
+ const chrono::nanoseconds elapsed_time =
+ monotonic_edge - last_posedge_monotonic;
+
+ last_posedge_monotonic = monotonic_edge;
+
+ // Verify that the values are sane.
+ if (fpga_sample_length > 2e-5 || fpga_sample_length < 0) {
+ continue;
+ }
+ if (fpga_offset < 0 || fpga_offset > 0.00015) {
+ continue;
+ }
+ if (elapsed_time > chrono::microseconds(5050) + chrono::microseconds(4) ||
+ elapsed_time < chrono::microseconds(5050) - chrono::microseconds(4)) {
+ continue;
+ }
+ // Good edge!
+ {
+ ::std::unique_lock<::aos::stl_mutex> locker(tick_time_mutex_);
+ last_tick_time_monotonic_timepoint_ = last_posedge_monotonic;
+ last_period_ = elapsed_time;
+ }
+ } else {
+ LOG(INFO, "PWM triggered %d\n", ret);
+ }
+ }
+ pwm_trigger_->CancelInterrupts();
+}
+
+} // namespace wpilib
+} // namespace frc971