motors/simple_receiver.cc

// This file has the main for the Teensy on the simple receiver board.

#include <inttypes.h>
#include <stdio.h>
#include <atomic>
#include <cmath>

#include "frc971/control_loops/drivetrain/polydrivetrain.h"
#include "motors/core/kinetis.h"
#include "motors/core/time.h"
#include "motors/peripheral/adc.h"
#include "motors/peripheral/can.h"
#include "motors/peripheral/configuration.h"
#include "motors/seems_reasonable/drivetrain_dog_motor_plant.h"
#include "motors/seems_reasonable/polydrivetrain_dog_motor_plant.h"
#include "motors/seems_reasonable/spring.h"
#include "motors/usb/cdc.h"
#include "motors/usb/usb.h"
#include "motors/util.h"

namespace frc971 {
namespace motors {
namespace {

using ::frc971::control_loops::drivetrain::DrivetrainConfig;
using ::frc971::control_loops::drivetrain::PolyDrivetrain;
using ::frc971::constants::ShifterHallEffect;
using ::frc971::control_loops::DrivetrainQueue_Goal;
using ::frc971::control_loops::DrivetrainQueue_Output;
using ::motors::seems_reasonable::Spring;

const ShifterHallEffect kThreeStateDriveShifter{0.0, 0.0, 0.25, 0.75};

const DrivetrainConfig<float> &GetDrivetrainConfig() {
  static DrivetrainConfig<float> kDrivetrainConfig{
      ::frc971::control_loops::drivetrain::ShifterType::NO_SHIFTER,
      ::frc971::control_loops::drivetrain::LoopType::OPEN_LOOP,
      ::frc971::control_loops::drivetrain::GyroType::SPARTAN_GYRO,
      ::frc971::control_loops::drivetrain::IMUType::IMU_X,

      ::motors::seems_reasonable::MakeDrivetrainLoop,
      ::motors::seems_reasonable::MakeVelocityDrivetrainLoop,
      ::std::function<StateFeedbackLoop<7, 2, 4, float>()>(),

      ::motors::seems_reasonable::kDt, ::motors::seems_reasonable::kRobotRadius,
      ::motors::seems_reasonable::kWheelRadius, ::motors::seems_reasonable::kV,

      ::motors::seems_reasonable::kHighGearRatio,
      ::motors::seems_reasonable::kLowGearRatio, kThreeStateDriveShifter,
      kThreeStateDriveShifter, true /* default_high_gear */,
      0 /* down_offset if using constants use
                                   constants::GetValues().down_error */, 0.8 /* wheel_non_linearity */,
      1.2 /* quickturn_wheel_multiplier */, 1.5 /* wheel_multiplier */,
  };

  return kDrivetrainConfig;
};


::std::atomic<teensy::AcmTty *> global_stdout{nullptr};

::std::atomic<PolyDrivetrain<float> *> global_polydrivetrain{nullptr};
::std::atomic<Spring *> global_spring{nullptr};

// Last width we received on each channel.
uint16_t pwm_input_widths[6];
// When we received a pulse on each channel in milliseconds.
uint32_t pwm_input_times[6];

constexpr int kChannelTimeout = 100;

bool lost_channel(int channel) {
  DisableInterrupts disable_interrupts;
  if (time_after(millis(),
                 time_add(pwm_input_times[channel], kChannelTimeout))) {
    return true;
  }
  return false;
}

// Returns the most recently captured value for the specified input channel
// scaled from -1 to 1, or 0 if it was captured over 100ms ago.
float convert_input_width(int channel) {
  uint16_t width;
  {
    DisableInterrupts disable_interrupts;
    if (time_after(millis(),
                   time_add(pwm_input_times[channel], kChannelTimeout))) {
      return 0;
    }

    width = pwm_input_widths[channel];
  }

  // Values measured with a channel mapped to a button.
  static constexpr uint16_t kMinWidth = 4133;
  static constexpr uint16_t kMaxWidth = 7177;
  if (width < kMinWidth) {
    width = kMinWidth;
  } else if (width > kMaxWidth) {
    width = kMaxWidth;
  }
  return (static_cast<float>(2 * (width - kMinWidth)) /
          static_cast<float>(kMaxWidth - kMinWidth)) -
         1.0f;
}

// Sends a SET_RPM command to the specified VESC.
// Note that sending 6 VESC commands every 1ms doesn't quite fit in the CAN
// bandwidth.
void vesc_set_rpm(int vesc_id, float rpm) {
  const int32_t rpm_int = rpm;
  uint32_t id = CAN_EFF_FLAG;
  id |= vesc_id;
  id |= (0x03 /* SET_RPM */) << 8;
  uint8_t data[4] = {
      static_cast<uint8_t>((rpm_int >> 24) & 0xFF),
      static_cast<uint8_t>((rpm_int >> 16) & 0xFF),
      static_cast<uint8_t>((rpm_int >> 8) & 0xFF),
      static_cast<uint8_t>((rpm_int >> 0) & 0xFF),
  };
  can_send(id, data, sizeof(data), 2 + vesc_id);
}

// Sends a SET_CURRENT command to the specified VESC.
// current is in amps.
// Note that sending 6 VESC commands every 1ms doesn't quite fit in the CAN
// bandwidth.
void vesc_set_current(int vesc_id, float current) {
  constexpr float kMaxCurrent = 80.0f;
  const int32_t current_int =
      ::std::max(-kMaxCurrent, ::std::min(kMaxCurrent, current)) * 1000.0f;
  uint32_t id = CAN_EFF_FLAG;
  id |= vesc_id;
  id |= (0x01 /* SET_CURRENT */) << 8;
  uint8_t data[4] = {
      static_cast<uint8_t>((current_int >> 24) & 0xFF),
      static_cast<uint8_t>((current_int >> 16) & 0xFF),
      static_cast<uint8_t>((current_int >> 8) & 0xFF),
      static_cast<uint8_t>((current_int >> 0) & 0xFF),
  };
  can_send(id, data, sizeof(data), 2 + vesc_id);
}

// Sends a SET_DUTY command to the specified VESC.
// duty is from -1 to 1.
// Note that sending 6 VESC commands every 1ms doesn't quite fit in the CAN
// bandwidth.
void vesc_set_duty(int vesc_id, float duty) {
  constexpr int32_t kMaxDuty = 99999;
  const int32_t duty_int = ::std::max(
      -kMaxDuty, ::std::min(kMaxDuty, static_cast<int32_t>(duty * 100000.0f)));
  uint32_t id = CAN_EFF_FLAG;
  id |= vesc_id;
  id |= (0x00 /* SET_DUTY */) << 8;
  uint8_t data[4] = {
      static_cast<uint8_t>((duty_int >> 24) & 0xFF),
      static_cast<uint8_t>((duty_int >> 16) & 0xFF),
      static_cast<uint8_t>((duty_int >> 8) & 0xFF),
      static_cast<uint8_t>((duty_int >> 0) & 0xFF),
  };
  can_send(id, data, sizeof(data), 2 + vesc_id);
}

void DoVescTest() {
  uint32_t time = micros();
  while (true) {
    for (int i = 0; i < 6; ++i) {
      const uint32_t end = time_add(time, 500000);
      while (true) {
        const bool done = time_after(micros(), end);
        float current;
        if (done) {
          current = -6;
        } else {
          current = 6;
        }
        vesc_set_current(i, current);
        if (done) {
          break;
        }
        delay(5);
      }
      time = end;
    }
  }
}

void DoReceiverTest2() {
  static constexpr float kMaxRpm = 10000.0f;
  while (true) {
    const bool flip = convert_input_width(2) > 0;

    {
      const float value = convert_input_width(0);

      {
        float rpm = ::std::min(0.0f, value) * kMaxRpm;
        if (flip) {
          rpm *= -1.0f;
        }
        vesc_set_rpm(0, rpm);
      }

      {
        float rpm = ::std::max(0.0f, value) * kMaxRpm;
        if (flip) {
          rpm *= -1.0f;
        }
        vesc_set_rpm(1, rpm);
      }
    }

    {
      const float value = convert_input_width(1);

      {
        float rpm = ::std::min(0.0f, value) * kMaxRpm;
        if (flip) {
          rpm *= -1.0f;
        }
        vesc_set_rpm(2, rpm);
      }

      {
        float rpm = ::std::max(0.0f, value) * kMaxRpm;
        if (flip) {
          rpm *= -1.0f;
        }
        vesc_set_rpm(3, rpm);
      }
    }

    {
      const float value = convert_input_width(4);

      {
        float rpm = ::std::min(0.0f, value) * kMaxRpm;
        if (flip) {
          rpm *= -1.0f;
        }
        vesc_set_rpm(4, rpm);
      }

      {
        float rpm = ::std::max(0.0f, value) * kMaxRpm;
        if (flip) {
          rpm *= -1.0f;
        }
        vesc_set_rpm(5, rpm);
      }
    }
    // Give the CAN frames a chance to go out.
    delay(5);
  }
}

void SetupPwmFtm(BigFTM *ftm) {
  ftm->MODE = FTM_MODE_WPDIS;
  ftm->MODE = FTM_MODE_WPDIS | FTM_MODE_FTMEN;
  ftm->SC = FTM_SC_CLKS(0) /* Disable counting for now */;

  // Can't change MOD according to the reference manual ("The Dual Edge Capture
  // mode must be used with ...  the FTM counter in Free running counter.").
  ftm->MOD = 0xFFFF;

  // Capturing rising edge.
  ftm->C0SC = FTM_CSC_MSA | FTM_CSC_ELSA;
  // Capturing falling edge.
  ftm->C1SC = FTM_CSC_CHIE | FTM_CSC_MSA | FTM_CSC_ELSB;

  // Capturing rising edge.
  ftm->C2SC = FTM_CSC_MSA | FTM_CSC_ELSA;
  // Capturing falling edge.
  ftm->C3SC = FTM_CSC_CHIE | FTM_CSC_MSA | FTM_CSC_ELSB;

  // Capturing rising edge.
  ftm->C4SC = FTM_CSC_MSA | FTM_CSC_ELSA;
  // Capturing falling edge.
  ftm->C5SC = FTM_CSC_CHIE | FTM_CSC_MSA | FTM_CSC_ELSB;

  // Capturing rising edge.
  ftm->C6SC = FTM_CSC_MSA | FTM_CSC_ELSA;
  // Capturing falling edge.
  ftm->C7SC = FTM_CSC_CHIE | FTM_CSC_MSA | FTM_CSC_ELSB;

  (void)ftm->STATUS;
  ftm->STATUS = 0x00;

  ftm->COMBINE = FTM_COMBINE_DECAP3 | FTM_COMBINE_DECAPEN3 |
                 FTM_COMBINE_DECAP2 | FTM_COMBINE_DECAPEN2 |
                 FTM_COMBINE_DECAP1 | FTM_COMBINE_DECAPEN1 |
                 FTM_COMBINE_DECAP0 | FTM_COMBINE_DECAPEN0;

  // 34.95ms max period before it starts wrapping and being weird.
  ftm->SC = FTM_SC_CLKS(1) /* Use the system clock */ |
            FTM_SC_PS(4) /* Prescaler=32 */;

  ftm->MODE &= ~FTM_MODE_WPDIS;
}

struct AccelerometerResult {
  uint16_t result;
  bool success;
};

// Does a transfer on the accelerometer. Returns the resulting frame, or a
// failure if it takes until after end_micros.
AccelerometerResult AccelerometerTransfer(uint16_t data, uint32_t end_micros) {
  SPI0_SR = SPI_SR_RFDF;
  SPI0_PUSHR = SPI_PUSHR_PCS(1) | data;

  while (!(SPI0_SR & SPI_SR_RFDF)) {
    if (time_after(micros(), end_micros)) {
      return {0, false};
    }
  }
  const uint32_t popr = SPI0_POPR;
  SPI0_SR = SPI_SR_RFDF;
  return {static_cast<uint16_t>(popr & 0xFFFF), true};
}

constexpr uint32_t kAccelerometerTimeout = 500;

bool AccelerometerWrite(uint8_t address, uint8_t data, uint32_t end_micros) {
  const AccelerometerResult r = AccelerometerTransfer(
      (static_cast<uint16_t>(address) << 8) | static_cast<uint16_t>(data),
      end_micros);
  return r.success;
}

AccelerometerResult AccelerometerRead(uint8_t address, uint32_t end_micros) {
  AccelerometerResult r = AccelerometerTransfer(
      (static_cast<uint16_t>(address) << 8) | UINT16_C(0x8000), end_micros);
  r.result = r.result & UINT16_C(0xFF);
  return r;
}

bool accelerometer_inited = false;

void AccelerometerInit() {
  accelerometer_inited = false;
  const uint32_t end_micros = time_add(micros(), kAccelerometerTimeout);
  {
    const auto who_am_i = AccelerometerRead(0xF, end_micros);
    if (!who_am_i.success) {
      return;
    }
    if (who_am_i.result != 0x32) {
      return;
    }
  }
  if (!AccelerometerWrite(
          0x20, (1 << 5) /* Normal mode */ | (1 << 3) /* 100 Hz */ |
                    (1 << 2) /* Z enabled */ | (1 << 1) /* Y enabled */ |
                    (1 << 0) /* X enabled */,
          end_micros)) {
  }
  // If want to read LSB, need to enable BDU to avoid splitting reads.
  if (!AccelerometerWrite(0x23, (0 << 6) /* Data LSB at lower address */ |
                                    (3 << 4) /* 400g full scale */ |
                                    (0 << 0) /* 4-wire interface */,
                          end_micros)) {
  }
  accelerometer_inited = true;
}

float AccelerometerConvert(uint16_t value) {
  return static_cast<float>(400.0 / 65536.0) * static_cast<float>(value);
}

// Returns the total acceleration (in any direction) or 0 if there's an error.
float ReadAccelerometer() {
  if (!accelerometer_inited) {
    AccelerometerInit();
    return 0;
  }

  const uint32_t end_micros = time_add(micros(), kAccelerometerTimeout);
  const auto x = AccelerometerRead(0x29, end_micros);
  const auto y = AccelerometerRead(0x2B, end_micros);
  const auto z = AccelerometerRead(0x2D, end_micros);
  if (!x.success || !y.success || !z.success) {
    accelerometer_inited = false;
    return 0;
  }

  const float x_g = AccelerometerConvert(x.result);
  const float y_g = AccelerometerConvert(y.result);
  const float z_g = AccelerometerConvert(z.result);
  return ::std::sqrt(x_g * x_g + y_g * y_g + z_g * z_g);
}

extern "C" void ftm0_isr() {
  while (true) {
    const uint32_t status = FTM0->STATUS;
    if (status == 0) {
      return;
    }

    if (status & (1 << 1)) {
      const uint32_t start = FTM0->C0V;
      const uint32_t end = FTM0->C1V;
      pwm_input_widths[0] = (end - start) & 0xFFFF;
      pwm_input_times[0] = millis();
    }
    if (status & (1 << 7)) {
      const uint32_t start = FTM0->C6V;
      const uint32_t end = FTM0->C7V;
      pwm_input_widths[1] = (end - start) & 0xFFFF;
      pwm_input_times[1] = millis();
    }
    if (status & (1 << 5)) {
      const uint32_t start = FTM0->C4V;
      const uint32_t end = FTM0->C5V;
      pwm_input_widths[2] = (end - start) & 0xFFFF;
      pwm_input_times[2] = millis();
    }
    if (status & (1 << 3)) {
      const uint32_t start = FTM0->C2V;
      const uint32_t end = FTM0->C3V;
      pwm_input_widths[4] = (end - start) & 0xFFFF;
      pwm_input_times[4] = millis();
    }

    FTM0->STATUS = 0;
  }
}

extern "C" void ftm3_isr() {
  while (true) {
    const uint32_t status = FTM3->STATUS;
    if (status == 0) {
      return;
    }

    if (status & (1 << 3)) {
      const uint32_t start = FTM3->C2V;
      const uint32_t end = FTM3->C3V;
      pwm_input_widths[3] = (end - start) & 0xFFFF;
      pwm_input_times[3] = millis();
    }
    if (status & (1 << 7)) {
      const uint32_t start = FTM3->C6V;
      const uint32_t end = FTM3->C7V;
      pwm_input_widths[5] = (end - start) & 0xFFFF;
      pwm_input_times[5] = millis();
    }

    FTM3->STATUS = 0;
  }
}

float ConvertEncoderChannel(uint16_t reading) {
  // Theoretical values based on the datasheet are 931 and 2917.
  // With these values, the magnitude ranges from 0.99-1.03, which works fine
  // (the encoder's output appears to get less accurate in one quadrant for some
  // reason, hence the variation).
  static constexpr uint16_t kMin = 802, kMax = 3088;
  if (reading < kMin) {
    reading = kMin;
  } else if (reading > kMax) {
    reading = kMax;
  }
  return (static_cast<float>(2 * (reading - kMin)) /
          static_cast<float>(kMax - kMin)) -
         1.0f;
}

struct EncoderReading {
  EncoderReading(const SimpleAdcReadings &adc_readings) {
    const float sin = ConvertEncoderChannel(adc_readings.sin);
    const float cos = ConvertEncoderChannel(adc_readings.cos);

    const float magnitude = hypot(sin, cos);
    const float magnitude_error = ::std::abs(magnitude - 1.0f);
    valid = magnitude_error < 0.30f;

    angle = ::std::atan2(sin, cos);
  }

  // Angle in radians, in [-pi, pi].
  float angle;

  bool valid;
};

extern "C" void pit3_isr() {
  PIT_TFLG3 = 1;
  PolyDrivetrain<float> *polydrivetrain =
      global_polydrivetrain.load(::std::memory_order_acquire);
  Spring *spring = global_spring.load(::std::memory_order_acquire);

  SimpleAdcReadings adc_readings;
  {
    DisableInterrupts disable_interrupts;
    adc_readings = AdcReadSimple(disable_interrupts);
  }

  EncoderReading encoder(adc_readings);
  static float last_good_encoder = 0.0f;
  static int invalid_encoder_count = 0;
  if (encoder.valid) {
    last_good_encoder = encoder.angle;
    invalid_encoder_count = 0;
  } else {
    ++invalid_encoder_count;
  }

  const bool lost_any_channel = lost_channel(0) || lost_channel(1) ||
                                lost_channel(2) || lost_channel(3) ||
                                lost_channel(4) ||
                                (::std::abs(convert_input_width(4)) < 0.5f);

  if (polydrivetrain != nullptr && spring != nullptr) {
    DrivetrainQueue_Goal goal;
    goal.control_loop_driving = false;
    if (lost_any_channel) {
      goal.throttle = 0.0f;
      goal.wheel = 0.0f;
    } else {
      goal.throttle = convert_input_width(1);
      goal.wheel = -convert_input_width(0);
    }
    goal.quickturn = ::std::abs(polydrivetrain->velocity()) < 0.25f;

    DrivetrainQueue_Output output;

    polydrivetrain->SetGoal(goal);
    polydrivetrain->Update();
    polydrivetrain->SetOutput(&output);

    vesc_set_duty(0, -output.left_voltage / 12.0f);
    vesc_set_duty(1, -output.left_voltage / 12.0f);

    vesc_set_duty(2, output.right_voltage / 12.0f);
    vesc_set_duty(3, output.right_voltage / 12.0f);

    bool prime = convert_input_width(2) > 0.1f;
    bool fire = convert_input_width(3) > 0.1f;

    bool unload = lost_any_channel;
    static bool was_lost = true;
    bool force_reset = !lost_any_channel && was_lost;
    was_lost = lost_any_channel;

    spring->Iterate(unload, prime, fire, force_reset, invalid_encoder_count <= 2,
                    last_good_encoder);

    float spring_output = spring->output();

    vesc_set_duty(4, -spring_output);
    vesc_set_duty(5, spring_output);

    const float accelerometer = ReadAccelerometer();
    (void)accelerometer;

    /*
     // Massive debug.  Turn on for useful bits.
    printf("acc %d/1000\n", (int)(accelerometer / 1000));
    if (!encoder.valid) {
      printf("Stuck encoder: ADC %" PRIu16 " %" PRIu16
             " enc %d/1000 %s mag %d\n",
             adc_readings.sin, adc_readings.cos, (int)(encoder.angle * 1000),
             encoder.valid ? "T" : "f",
             (int)(hypot(ConvertEncoderChannel(adc_readings.sin),
                         ConvertEncoderChannel(adc_readings.cos)) *
                   1000));
    }
    static int i = 0;
    ++i;
    if (i > 20) {
      i = 0;
      if (lost_any_channel) {
        printf("200Hz loop, disabled %d %d %d %d %d\n",
               (int)(convert_input_width(0) * 1000),
               (int)(convert_input_width(1) * 1000),
               (int)(convert_input_width(2) * 1000),
               (int)(convert_input_width(3) * 1000),
               (int)(convert_input_width(4) * 1000));
      } else {
        printf(
            "TODO(Austin): 200Hz loop %d %d %d %d %d, lr, %d, %d velocity %d "
            " state: %d, near %d angle %d goal %d to: %d ADC %" PRIu16
            " %" PRIu16 " enc %d/1000 %s from %d\n",
            (int)(convert_input_width(0) * 1000),
            (int)(convert_input_width(1) * 1000),
            (int)(convert_input_width(2) * 1000),
            (int)(convert_input_width(3) * 1000),
            (int)(convert_input_width(4) * 1000),
            static_cast<int>(output.left_voltage * 100),
            static_cast<int>(output.right_voltage * 100),
            static_cast<int>(polydrivetrain->velocity() * 100),
            static_cast<int>(spring->state()), static_cast<int>(spring->Near()),
            static_cast<int>(spring->angle() * 1000),
            static_cast<int>(spring->goal() * 1000),
            static_cast<int>(spring->timeout()), adc_readings.sin,
            adc_readings.cos, (int)(encoder.angle * 1000),
            encoder.valid ? "T" : "f",
            (int)(::std::sqrt(ConvertEncoderChannel(adc_readings.sin) *
                                  ConvertEncoderChannel(adc_readings.sin) +
                              ConvertEncoderChannel(adc_readings.cos) *
                                  ConvertEncoderChannel(adc_readings.cos)) *
                  1000));
      }
    }
    */
  }
}

}  // namespace

extern "C" {

void *__stack_chk_guard = (void *)0x67111971;

int _write(int /*file*/, char *ptr, int len) {
  teensy::AcmTty *const tty = global_stdout.load(::std::memory_order_acquire);
  if (tty != nullptr) {
    return tty->Write(ptr, len);
  }
  return 0;
}

void __stack_chk_fail(void);

}  // extern "C"

extern "C" int main(void) {
  // for background about this startup delay, please see these conversations
  // https://forum.pjrc.com/threads/36606-startup-time-(400ms)?p=113980&viewfull=1#post113980
  // https://forum.pjrc.com/threads/31290-Teensey-3-2-Teensey-Loader-1-24-Issues?p=87273&viewfull=1#post87273
  delay(400);

  // Set all interrupts to the second-lowest priority to start with.
  for (int i = 0; i < NVIC_NUM_INTERRUPTS; i++) NVIC_SET_SANE_PRIORITY(i, 0xD);

  // Now set priorities for all the ones we care about. They only have meaning
  // relative to each other, which means centralizing them here makes it a lot
  // more manageable.
  NVIC_SET_SANE_PRIORITY(IRQ_USBOTG, 0x7);
  NVIC_SET_SANE_PRIORITY(IRQ_FTM0, 0xa);
  NVIC_SET_SANE_PRIORITY(IRQ_FTM3, 0xa);
  NVIC_SET_SANE_PRIORITY(IRQ_PIT_CH3, 0x5);

  // Builtin LED.
  PERIPHERAL_BITBAND(GPIOC_PDOR, 5) = 1;
  PORTC_PCR5 = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(1);
  PERIPHERAL_BITBAND(GPIOC_PDDR, 5) = 1;

  // Set up the CAN pins.
  PORTA_PCR12 = PORT_PCR_DSE | PORT_PCR_MUX(2);
  PORTA_PCR13 = PORT_PCR_DSE | PORT_PCR_MUX(2);

  // PWM_IN0
  // FTM0_CH0
  PORTC_PCR1 = PORT_PCR_MUX(4);

  // PWM_IN1
  // FTM0_CH6
  PORTD_PCR6 = PORT_PCR_MUX(4);

  // PWM_IN2
  // FTM0_CH4
  PORTD_PCR4 = PORT_PCR_MUX(4);

  // PWM_IN3
  // FTM3_CH2
  PORTD_PCR2 = PORT_PCR_MUX(4);

  // PWM_IN4
  // FTM0_CH2
  PORTC_PCR3 = PORT_PCR_MUX(4);

  // PWM_IN5
  // FTM3_CH6
  PORTC_PCR10 = PORT_PCR_MUX(3);

  // SPI0
  // ACC_CS PCS0
  PORTA_PCR14 = PORT_PCR_DSE | PORT_PCR_MUX(2);
  // SCK
  PORTA_PCR15 = PORT_PCR_DSE | PORT_PCR_MUX(2);
  // MOSI
  PORTA_PCR16 = PORT_PCR_DSE | PORT_PCR_MUX(2);
  // MISO
  PORTA_PCR17 = PORT_PCR_DSE | PORT_PCR_MUX(2);

  SIM_SCGC6 |= SIM_SCGC6_SPI0;
  SPI0_MCR = SPI_MCR_MSTR | SPI_MCR_PCSIS(1) | SPI_MCR_CLR_TXF |
             SPI_MCR_CLR_RXF | SPI_MCR_HALT;
  // 60 MHz "protocol clock"
  // 6ns CS setup
  // 8ns CS hold
  SPI0_CTAR0 = SPI_CTAR_FMSZ(15) | SPI_CTAR_CPOL /* Clock idles high */ |
               SPI_CTAR_CPHA /* Data captured on trailing edge */ |
               0 /* !LSBFE MSB first */ |
               SPI_CTAR_PCSSCK(0) /* PCS->SCK prescaler = 1 */ |
               SPI_CTAR_PASC(0) /* SCK->PCS prescaler = 1 */ |
               SPI_CTAR_PDT(0) /* PCS->PCS prescaler = 1 */ |
               SPI_CTAR_PBR(0) /* baud prescaler = 1 */ |
               SPI_CTAR_CSSCK(0) /* PCS->SCK 2/60MHz = 33.33ns */ |
               SPI_CTAR_ASC(0) /* SCK->PCS 2/60MHz = 33.33ns */ |
               SPI_CTAR_DT(2) /* PCS->PSC 8/60MHz = 133.33ns */ |
               SPI_CTAR_BR(2) /* BR 60MHz/6 = 10MHz */;

  SPI0_MCR &= ~SPI_MCR_HALT;

  delay(100);

  teensy::UsbDevice usb_device(0, 0x16c0, 0x0492);
  usb_device.SetManufacturer("Seems Reasonable LLC");
  usb_device.SetProduct("Simple Receiver Board");

  teensy::AcmTty tty0(&usb_device);
  global_stdout.store(&tty0, ::std::memory_order_release);
  usb_device.Initialize();

  SIM_SCGC6 |= SIM_SCGC6_PIT;
  // Workaround for errata e7914.
  (void)PIT_MCR;
  PIT_MCR = 0;
  PIT_LDVAL3 = (BUS_CLOCK_FREQUENCY / 200) - 1;
  PIT_TCTRL3 = PIT_TCTRL_TIE | PIT_TCTRL_TEN;

  can_init(0, 1);
  AdcInitSimple();
  SetupPwmFtm(FTM0);
  SetupPwmFtm(FTM3);

  PolyDrivetrain<float> polydrivetrain(GetDrivetrainConfig(), nullptr);
  global_polydrivetrain.store(&polydrivetrain, ::std::memory_order_release);
  Spring spring;
  global_spring.store(&spring, ::std::memory_order_release);

  // Leave the LEDs on for a bit longer.
  delay(300);
  printf("Done starting up\n");

  AccelerometerInit();
  printf("Accelerometer init %s\n", accelerometer_inited ? "success" : "fail");

  // Done starting up, now turn the LED off.
  PERIPHERAL_BITBAND(GPIOC_PDOR, 5) = 0;

  NVIC_ENABLE_IRQ(IRQ_FTM0);
  NVIC_ENABLE_IRQ(IRQ_FTM3);
  NVIC_ENABLE_IRQ(IRQ_PIT_CH3);

  while (true) {
  }

  return 0;
}

void __stack_chk_fail(void) {
  while (true) {
    GPIOC_PSOR = (1 << 5);
    printf("Stack corruption detected\n");
    delay(1000);
    GPIOC_PCOR = (1 << 5);
    delay(1000);
  }
}

}  // namespace motors
}  // namespace frc971