Brooklyn/gnuk/chopstx/example-fs-bb48/touch.c

#include <stdint.h>
#include <stdlib.h>
#include <chopstx.h>
#include <mcu/mkl27z.h>

struct TPM {
  volatile uint32_t SC;
  volatile uint32_t CNT;
  volatile uint32_t MOD;
  volatile uint32_t C0SC;
  volatile uint32_t C0V;
  volatile uint32_t C1SC;
  volatile uint32_t C1V;
  uint32_t rsvd0[13];
  volatile uint32_t STATUS;
  uint32_t rsvd1[7];
  volatile uint32_t POL;
  uint32_t rsvd2[4];
  volatile uint32_t CONF;
};

static struct TPM *const TPM1 = (struct TPM *)0x40039000;

static chopstx_intr_t tpm1_intr;
#define INTR_REQ_TPM1 18

static void
gpio_assert_low (void)
{
  /* Assert LOW.  */ 
  PORTB->PCR1 = (1<<8) /* GPIO                  */
              | (0<<6) /* DriveStrengthEnable=0 */
              | (0<<4) /* PassiveFilterEnable=0 */
              | (1<<2) /* SlewRateEnable = slow */
              | (0<<1) /* pull enable = 0       */ 
              | (0<<0) /* pull up select= 0         */
              ;

  GPIOB->PCOR = (1 << 1);            /* PTB1: Clear: Output 0  */
}

uint16_t
touch_get (void)
{
  chopstx_prio_t prio_old;
  uint16_t v;

  prio_old = chopstx_setpriority (CHOPSTX_PRIO_INHIBIT_PREEMPTION);
  /* 
   * Start the timer's counter. 
   * TOF clear, TOIE=1, CPWMS=0, CMOD=1, PS=011.
   */
  TPM1->SC = 0xcb;

  /* Let the register to pull it up.  */
  PORTB->PCR1 = (3<<8) /* TPM1_CH1              */
              | (0<<6) /* DriveStrengthEnable=0 */
              | (0<<4) /* PassiveFilterEnable=0 */
              | (1<<2) /* SlewRateEnable = slow */
              | (0<<1) /* pull enable = 0       */ 
              | (0<<0) /* pullup select= 0      */
              ;

  chopstx_setpriority (prio_old);

  chopstx_intr_wait (&tpm1_intr);
  gpio_assert_low ();

  v = TPM1->C1V;

  /* Clear overflow and CH1 capture.  */
  TPM1->STATUS = 0x102;
  /* Stop the timer.  */
  TPM1->SC = 0;
  TPM1->CNT = 0xffff;	   /* Writing causes reset of the counter.  */

  chopstx_intr_done (&tpm1_intr);
  return v;
}


void
touch_init (void)
{
  chopstx_claim_irq (&tpm1_intr, INTR_REQ_TPM1);

  /* Input capture mode: MSB = 0, MSA = 0 */
  /*   Rising edge: ELSB=0 ELSA=1 */
  TPM1->C1SC = 0x84;
  TPM1->POL=0;

  /* No trigger.   */
  /* Stop on overflow: CSOO=1 */ 
  /* Run the timer in the debug mode */
  TPM1->CONF = 0x000200c0;

  TPM1->CNT = 0xffff;	   /* Writing causes reset of the counter.  */
  gpio_assert_low ();
}