InputCapture.cpp

#include <Arduino.h>
#include "InputCapture.h"

#define ENET_TCSR_TPWC(n)          (((n) & 0b11111)<<11)
#define ENET_TCSR_TF               (1<<7)
#define ENET_TCSR_TIE              (1<<6)
#define ENET_TCSR_TMODE_MASK       (0b1111<<2)
#define ENET_TCSR_TMODE_DISABLED   0
#define ENET_TCSR_TMODE_IC_RISING  (0b0001<<2)
#define ENET_TCSR_TMODE_IC_FALLING (0b0010<<2)
#define ENET_TCSR_TMODE_IC_BOTH    (0b0011<<2)
#define ENET_TCSR_TMODE_OC_SOFT    (0b0100<<2)
#define ENET_TCSR_TMODE_OC_TOGGLE  (0b0101<<2)
#define ENET_TCSR_TMODE_OC_CLEAR   (0b0110<<2)
#define ENET_TCSR_TMODE_OC_SET     (0b0111<<2)
#define ENET_TCSR_TMODE_OC_CCSO    (0b1010<<2)
#define ENET_TCSR_TMODE_OC_SCCO    (0b1011<<2)
#define ENET_TCSR_TMODE_OC_PULSE0  (0b1110<<2)
#define ENET_TCSR_TMODE_OC_PULSE1  (0b1111<<2)

static void interrupt_1588_timer() {
  if(ENET_TCSR0 & ENET_TCSR_TF) {
    ENET_TCSR0 = ENET_TCSR0;
    pps.newCapture(ENET_TCCR0);
  }
  asm("dsb"); // allow write to complete so the interrupt doesn't fire twice
}

void InputCapture::newCapture(uint32_t count) {
  captures++;
  lastCount = count;
  lastMillis = millis();
}

InputCapture::InputCapture() {
  lastCount = 0;
  lastMillis = 0;
  captures = 0;
}

// TODO: this is hardcoded to pin35, channel 0
void InputCapture::begin() {
  attachInterruptVector(IRQ_ENET_TIMER, interrupt_1588_timer);
  NVIC_ENABLE_IRQ(IRQ_ENET_TIMER);

  // disable channel 0 to configure it
  ENET_TCSR0 = 0;

  // GPS PPS
  // peripherial: ENET_1588_EVENT0_IN
  // IOMUX: ALT3
  // teensy pin: 35
  IOMUXC_SW_MUX_CTL_PAD_GPIO_B1_12 = 3;
  // route B1_12 to 1588 timer
  IOMUXC_ENET0_TIMER_SELECT_INPUT = 0b10;

  // wait for disable to cross clock domains
  while(ENET_TCSR0 & ENET_TCSR_TMODE_MASK) {}
  // enable rising edge and interrupts from GPS PPS
  ENET_TCSR0 = ENET_TCSR_TMODE_IC_RISING | ENET_TCSR_TIE;  
}