circuitpython/ports/nrf/common-hal/pulseio/PulseIn.c

/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "common-hal/pulseio/PulseIn.h"

#include <stdint.h>
#include <string.h>

#include "nrf/timers.h"
#include "py/mpconfig.h"
#include "py/gc.h"
#include "py/runtime.h"

#include "shared-bindings/microcontroller/__init__.h"
#include "shared-bindings/pulseio/PulseIn.h"

#include "nrfx_gpiote.h"

// obj array to map pin -> self since nrfx hide the mapping
static pulseio_pulsein_obj_t *_objs[GPIOTE_CH_NUM];

// A single timer is shared amongst all PulseIn objects as a common high speed clock reference.
static uint8_t refcount = 0;
static nrfx_timer_t *timer = NULL;

static uint32_t overflow_count = 0;

static void timer_overflow_event_handler(nrf_timer_event_t event_type, void *p_context) {
    if (event_type != NRF_TIMER_EVENT_COMPARE0) {
        // Other event.
        return;
    }
    overflow_count++;
}

// return index of the object in array
static int _find_pulsein_obj(pulseio_pulsein_obj_t *obj) {
    for (size_t i = 0; i < NRFX_ARRAY_SIZE(_objs); i++) {
        if (_objs[i] == obj) {
            return i;
        }
    }

    return -1;
}

static void _pulsein_handler(nrfx_gpiote_pin_t pin, nrf_gpiote_polarity_t action) {
    // Grab the current time first.
    uint32_t current_overflow = overflow_count;
    uint32_t current_count = nrfx_timer_capture(timer, 1);

    pulseio_pulsein_obj_t *self = NULL;
    for (size_t i = 0; i < NRFX_ARRAY_SIZE(_objs); i++) {
        if (_objs[i] && _objs[i]->pin == pin) {
            self = _objs[i];
            break;
        }
    }
    if (!self) {
        return;
    }

    if (self->first_edge) {
        // first pulse is opposite state from idle
        bool state = nrf_gpio_pin_read(self->pin);
        if (self->idle_state != state) {
            self->first_edge = false;
        }
    } else {
        uint32_t total_diff = current_count + 0xffff * (current_overflow - self->last_overflow) - self->last_count;

        // Cap duration at 16 bits.
        uint16_t duration = 0xffff;
        if (total_diff < duration) {
            duration = total_diff;
        }

        uint16_t i = (self->start + self->len) % self->maxlen;
        self->buffer[i] = duration;
        if (self->len < self->maxlen) {
            self->len++;
        } else {
            self->start = (self->start + 1) % self->maxlen;
        }
    }

    self->last_overflow = current_overflow;
    self->last_count = current_count;
}

void pulsein_reset(void) {
    if (timer != NULL) {
        nrf_peripherals_free_timer(timer);
    }
    refcount = 0;

    memset(_objs, 0, sizeof(_objs));
}

void common_hal_pulseio_pulsein_construct(pulseio_pulsein_obj_t *self, const mcu_pin_obj_t *pin, uint16_t maxlen, bool idle_state) {
    int idx = _find_pulsein_obj(NULL);
    if (idx < 0) {
        mp_raise_NotImplementedError(NULL);
    }
    _objs[idx] = self;

    self->buffer = (uint16_t *)m_malloc(maxlen * sizeof(uint16_t));
    if (self->buffer == NULL) {
        m_malloc_fail(maxlen * sizeof(uint16_t));
    }

    if (refcount == 0) {
        timer = nrf_peripherals_allocate_timer();
        if (timer == NULL) {
            mp_raise_RuntimeError(MP_ERROR_TEXT("All timers in use"));
        }
        overflow_count = 0;

        nrfx_timer_config_t timer_config = {
            // PulseIn durations are in microseconds, so this is convenient.
            .frequency = NRF_TIMER_FREQ_1MHz,
            .mode = NRF_TIMER_MODE_TIMER,
            .bit_width = NRF_TIMER_BIT_WIDTH_32,
            .interrupt_priority = NRFX_TIMER_DEFAULT_CONFIG_IRQ_PRIORITY,
        };

        nrfx_timer_init(timer, &timer_config, &timer_overflow_event_handler);
        // Interrupt on overflow so we can track when it rolls over.
        nrfx_timer_compare(timer, NRF_TIMER_CC_CHANNEL0, 0, true);
        nrfx_timer_resume(timer);
    }
    refcount++;

    self->pin = pin->number;
    self->maxlen = maxlen;
    self->idle_state = idle_state;
    self->start = 0;
    self->len = 0;
    self->first_edge = true;
    self->paused = false;
    self->last_overflow = 0;
    self->last_count = 0;

    claim_pin(pin);

    nrfx_gpiote_in_config_t cfg = {
        .sense = NRF_GPIOTE_POLARITY_TOGGLE,
        .pull = NRF_GPIO_PIN_NOPULL, // idle_state ? NRF_GPIO_PIN_PULLDOWN : NRF_GPIO_PIN_PULLUP,
        .is_watcher = false, // nrf_gpio_cfg_watcher vs nrf_gpio_cfg_input
        .hi_accuracy = true,
        .skip_gpio_setup = false
    };
    nrfx_err_t err = nrfx_gpiote_in_init(self->pin, &cfg, _pulsein_handler);
    if (err != NRFX_SUCCESS) {
        mp_raise_RuntimeError(MP_ERROR_TEXT("All channels in use"));
    }
    nrfx_gpiote_in_event_enable(self->pin, true);
}

bool common_hal_pulseio_pulsein_deinited(pulseio_pulsein_obj_t *self) {
    return self->pin == NO_PIN;
}

void common_hal_pulseio_pulsein_deinit(pulseio_pulsein_obj_t *self) {
    if (common_hal_pulseio_pulsein_deinited(self)) {
        return;
    }

    nrfx_gpiote_in_event_disable(self->pin);
    nrfx_gpiote_in_uninit(self->pin);

    // mark local array as invalid
    int idx = _find_pulsein_obj(self);
    if (idx < 0) {
        mp_raise_NotImplementedError(NULL);
    }
    _objs[idx] = NULL;

    reset_pin_number(self->pin);
    self->pin = NO_PIN;

    refcount--;
    if (refcount == 0) {
        nrf_peripherals_free_timer(timer);
    }
}

void common_hal_pulseio_pulsein_pause(pulseio_pulsein_obj_t *self) {
    nrfx_gpiote_in_event_disable(self->pin);
    self->paused = true;
}

void common_hal_pulseio_pulsein_resume(pulseio_pulsein_obj_t *self, uint16_t trigger_duration) {
    // Make sure we're paused.
    if (!self->paused) {
        common_hal_pulseio_pulsein_pause(self);
    }

    // Send the trigger pulse.
    if (trigger_duration > 0) {
        nrfx_gpiote_in_uninit(self->pin);

        nrf_gpio_cfg_output(self->pin);
        nrf_gpio_pin_write(self->pin, !self->idle_state);
        common_hal_mcu_delay_us((uint32_t)trigger_duration);
        nrf_gpio_pin_write(self->pin, self->idle_state);

        nrfx_gpiote_in_config_t cfg = {
            .sense = NRF_GPIOTE_POLARITY_TOGGLE,
            .pull = NRF_GPIO_PIN_NOPULL, // idle_state ? NRF_GPIO_PIN_PULLDOWN : NRF_GPIO_PIN_PULLUP,
            .is_watcher = false, // nrf_gpio_cfg_watcher vs nrf_gpio_cfg_input
            .hi_accuracy = true,
            .skip_gpio_setup = false
        };
        nrfx_gpiote_in_init(self->pin, &cfg, _pulsein_handler);
    }

    self->first_edge = true;
    self->paused = false;
    self->last_overflow = 0;
    self->last_count = 0;

    nrfx_gpiote_in_event_enable(self->pin, true);
}

void common_hal_pulseio_pulsein_clear(pulseio_pulsein_obj_t *self) {
    if (!self->paused) {
        nrfx_gpiote_in_event_disable(self->pin);
    }

    self->start = 0;
    self->len = 0;

    if (!self->paused) {
        nrfx_gpiote_in_event_enable(self->pin, true);
    }
}

uint16_t common_hal_pulseio_pulsein_get_item(pulseio_pulsein_obj_t *self, int16_t index) {
    if (!self->paused) {
        nrfx_gpiote_in_event_disable(self->pin);
    }

    if (index < 0) {
        index += self->len;
    }
    if (index < 0 || index >= self->len) {
        if (!self->paused) {
            nrfx_gpiote_in_event_enable(self->pin, true);
        }
        mp_raise_IndexError_varg(MP_ERROR_TEXT("%q out of range"), MP_QSTR_index);
    }
    uint16_t value = self->buffer[(self->start + index) % self->maxlen];

    if (!self->paused) {
        nrfx_gpiote_in_event_enable(self->pin, true);
    }

    return value;
}

uint16_t common_hal_pulseio_pulsein_popleft(pulseio_pulsein_obj_t *self) {
    if (self->len == 0) {
        mp_raise_IndexError_varg(MP_ERROR_TEXT("pop from empty %q"), MP_QSTR_PulseIn);
    }

    if (!self->paused) {
        nrfx_gpiote_in_event_disable(self->pin);
    }

    uint16_t value = self->buffer[self->start];
    self->start = (self->start + 1) % self->maxlen;
    self->len--;

    if (!self->paused) {
        nrfx_gpiote_in_event_enable(self->pin, true);
    }

    return value;
}

uint16_t common_hal_pulseio_pulsein_get_maxlen(pulseio_pulsein_obj_t *self) {
    return self->maxlen;
}

bool common_hal_pulseio_pulsein_get_paused(pulseio_pulsein_obj_t *self) {
    return self->paused;
}

uint16_t common_hal_pulseio_pulsein_get_len(pulseio_pulsein_obj_t *self) {
    return self->len;
}