wiring_int.c

/*
  Arduino.c -  Partial implementation of the Wiring API for the Raspberry Pi
  Copyright (c) 2015 Hristo Gochkov.  All right reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include "Arduino.h"
#include "bcm2835_registers.h"

typedef struct {
        uint8_t mode;
        void (*fn)(void);
} isr_handler_t;

pthread_t _pin_isr_thread;
static isr_handler_t isr_handlers[64];
static volatile uint64_t _pin_isr_reg = 0;
static volatile uint64_t _pin_isr_last = 0;

void *isr_executor_task(void *isr_num){
    isr_handler_t *handler = &isr_handlers[(int)isr_num];
    handler->fn();
    pthread_exit(NULL);
}

void *_isr_check_task(void *arg __attribute__((unused))){
    while(_pin_isr_reg != 0){
        uint64_t state = GPLEV0;
        if(_pin_isr_reg >> 32) {
            state |= (uint64_t)GPLEV1 << 32;
        }
        state &= _pin_isr_reg;
        int i = 0;
        uint32_t changed = state ^ _pin_isr_last;
        if(changed){
            _pin_isr_last = state;
            while(changed){
                while(!(changed & _BV(i))) {
                    i++;
                }
                changed &= ~_BV(i);
                isr_handler_t *handler = &isr_handlers[i];
                if((state & _BV(i)) == 0 && (handler->mode == FALLING || handler->mode == CHANGE) && handler->fn) {
                    thread_create(isr_executor_task, (void *)i);
                } else if((state & _BV(i)) != 0 && (handler->mode == RISING || handler->mode == CHANGE) && handler->fn) {
                    thread_create(isr_executor_task, (void *)i);
                }
            }
        }
        if(_pin_isr_reg > 0)
            usleep(100);
    }
    pthread_exit(NULL);
}

void attachInterrupt(uint8_t pin, void (*userFunc)(void), int mode) {
    if(pin < 46) {
        uint8_t start = _pin_isr_reg == 0;
        isr_handler_t *handler = &isr_handlers[pin];
        handler->mode = mode;
        handler->fn = userFunc;
        _pin_isr_last |= (digitalRead(pin) << pin);
        _pin_isr_reg |= _BV(pin);
        if(start && pthread_create(&_pin_isr_thread, NULL, _isr_check_task, NULL) == 0){
            pthread_setname_np(_pin_isr_thread, "arduino-isr");
            pthread_detach(_pin_isr_thread);
        }
    }
}

void detachInterrupt(uint8_t pin) {
    if(pin < 46) {
        isr_handler_t *handler = &isr_handlers[pin];
        _pin_isr_reg &= ~_BV(pin);
        handler->mode = 0;
        handler->fn = 0;
    }
}