circuitpython/ports/atmel-samd/common-hal/pulseio/PulseOut.c

/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2016 Damien P. George
 *
 * 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/PulseOut.h"

#include <stdint.h>

#include "hal/include/hal_gpio.h"

#include "mpconfigport.h"
#include "peripherals/pins.h"
#include "peripherals/timers.h"
#include "py/gc.h"
#include "py/runtime.h"
#include "shared-bindings/pulseio/PulseOut.h"

// This timer is shared amongst all PulseOut objects under the assumption that
// the code is single threaded.
static uint8_t refcount = 0;

static uint8_t pulseout_tc_index = 0xff;

static __IO PORT_PINCFG_Type *active_pincfg = NULL;
static uint16_t *pulse_buffer = NULL;
static volatile uint16_t pulse_index = 0;
static uint16_t pulse_length;
static volatile uint32_t current_compare = 0;

static void turn_on(__IO PORT_PINCFG_Type * pincfg) {
    pincfg->reg = PORT_PINCFG_PMUXEN;
}

static void turn_off(__IO PORT_PINCFG_Type * pincfg) {
    pincfg->reg = PORT_PINCFG_RESETVALUE;
}

void pulse_finish(void) {
    pulse_index++;

    if (active_pincfg == NULL) {
        return;
    }
    // Always turn it off.
    turn_off(active_pincfg);
    if (pulse_index >= pulse_length) {
        return;
    }
    current_compare = (current_compare + pulse_buffer[pulse_index] * 3 / 4) & 0xffff;
    Tc* tc = tc_insts[pulseout_tc_index];
    tc->COUNT16.CC[0].reg = current_compare;
    if (pulse_index % 2 == 0) {
        turn_on(active_pincfg);
    }
}

void pulseout_interrupt_handler(uint8_t index) {
    if (index != pulseout_tc_index) return;
    Tc* tc = tc_insts[index];
    if (!tc->COUNT16.INTFLAG.bit.MC0) return;

    pulse_finish();

    // Clear the interrupt bit.
    tc->COUNT16.INTFLAG.reg = TC_INTFLAG_MC0;
}

void pulseout_reset() {
    refcount = 0;
    pulseout_tc_index = 0xff;
    active_pincfg = NULL;
}

void common_hal_pulseio_pulseout_construct(pulseio_pulseout_obj_t* self,
                                            const pulseio_pwmout_obj_t* carrier) {
    if (refcount == 0) {
        // Find a spare timer.
        Tc *tc = NULL;
        int8_t index = TC_INST_NUM - 1;
        for (; index >= 0; index--) {
            if (tc_insts[index]->COUNT16.CTRLA.bit.ENABLE == 0) {
                tc = tc_insts[index];
                break;
            }
        }
        if (tc == NULL) {
            mp_raise_RuntimeError("All timers in use");
        }

        pulseout_tc_index = index;

        // We use GCLK0 for SAMD21 and GCLK1 for SAMD51 because they both run at 48mhz making our
        // math the same across the boards.
        #ifdef SAMD21
        turn_on_clocks(true, index, 0);
        #endif
        #ifdef SAMD51
        turn_on_clocks(true, index, 1);
        #endif


        #ifdef SAMD21
        tc->COUNT16.CTRLA.reg = TC_CTRLA_MODE_COUNT16 |
                                TC_CTRLA_PRESCALER_DIV64 |
                                TC_CTRLA_WAVEGEN_NFRQ;
        #endif
        #ifdef SAMD51
        tc_reset(tc);
        tc_set_enable(tc, false);
        tc->COUNT16.CTRLA.reg = TC_CTRLA_MODE_COUNT16 | TC_CTRLA_PRESCALER_DIV64;
        tc->COUNT16.WAVE.reg = TC_WAVE_WAVEGEN_NFRQ;
        #endif

        tc_set_enable(tc, true);
        tc->COUNT16.CTRLBSET.reg = TC_CTRLBSET_CMD_STOP;
    }
    refcount++;

    self->pin = carrier->pin->pin;

    PortGroup *const port_base = &PORT->Group[GPIO_PORT(self->pin)];
    self->pincfg = &port_base->PINCFG[self->pin % 32];

    // Set the port to output a zero.
    port_base->OUTCLR.reg = 1 << (self->pin % 32);
    port_base->DIRSET.reg = 1 << (self->pin % 32);

    // Turn off the pinmux which should connect the port output.
    turn_off(self->pincfg);
}

bool common_hal_pulseio_pulseout_deinited(pulseio_pulseout_obj_t* self) {
    return self->pin == NO_PIN;
}

void common_hal_pulseio_pulseout_deinit(pulseio_pulseout_obj_t* self) {
    if (common_hal_pulseio_pulseout_deinited(self)) {
        return;
    }
    PortGroup *const port_base = &PORT->Group[GPIO_PORT(self->pin)];
    port_base->DIRCLR.reg = 1 << (self->pin % 32);

    turn_on(self->pincfg);

    refcount--;
    if (refcount == 0) {
        tc_reset(tc_insts[pulseout_tc_index]);
        pulseout_tc_index = 0xff;
    }
    self->pin = NO_PIN;
}

void common_hal_pulseio_pulseout_send(pulseio_pulseout_obj_t* self, uint16_t* pulses, uint16_t length) {
    if (active_pincfg != NULL) {
        mp_raise_RuntimeError("Another send is already active");
    }
    active_pincfg = self->pincfg;
    pulse_buffer = pulses;
    pulse_index = 0;
    pulse_length = length;

    current_compare = pulses[0] * 3 / 4;
    Tc* tc = tc_insts[pulseout_tc_index];
    tc->COUNT16.CC[0].reg = current_compare;

    // Clear our interrupt in case it was set earlier
    tc->COUNT16.INTFLAG.reg = TC_INTFLAG_MC0;
    tc->COUNT16.INTENSET.reg = TC_INTENSET_MC0;
    tc_enable_interrupts(pulseout_tc_index);
    turn_on(active_pincfg);
    tc->COUNT16.CTRLBSET.reg = TC_CTRLBSET_CMD_RETRIGGER;

    while(pulse_index < length) {
        // Do other things while we wait. The interrupts will handle sending the
        // signal.
        #ifdef MICROPY_VM_HOOK_LOOP
            MICROPY_VM_HOOK_LOOP
        #endif
    }

    tc->COUNT16.CTRLBSET.reg = TC_CTRLBSET_CMD_STOP;
    tc->COUNT16.INTENCLR.reg = TC_INTENCLR_MC0;
    tc_disable_interrupts(pulseout_tc_index);
    active_pincfg = NULL;
}