frc971/wpilib/sensor_reader.cc

#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