circuitpython/ports/atmel-samd/tick.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 "tick.h"

#include "peripheral_clk_config.h"

#include "supervisor/shared/autoreload.h"
#include "shared-module/gamepad/__init__.h"
#include "shared-bindings/microcontroller/Processor.h"

// Global millisecond tick count
volatile uint64_t ticks_ms = 0;

void SysTick_Handler(void) {
    // SysTick interrupt handler called when the SysTick timer reaches zero
    // (every millisecond).
    ticks_ms += 1;

    #ifdef CIRCUITPY_AUTORELOAD_DELAY_MS
        autoreload_tick();
    #endif
    #ifdef CIRCUITPY_GAMEPAD_TICKS
    if (!(ticks_ms & CIRCUITPY_GAMEPAD_TICKS)) {
        gamepad_tick();
    }
    #endif
}

void tick_init() {
    uint32_t ticks_per_ms = common_hal_mcu_processor_get_frequency() / 1000;
    SysTick_Config(ticks_per_ms-1);
    NVIC_EnableIRQ(SysTick_IRQn);
}

void tick_delay(uint32_t us) {
    uint32_t ticks_per_us = common_hal_mcu_processor_get_frequency() / 1000 / 1000;
    uint32_t us_until_next_tick = SysTick->VAL / ticks_per_us;
    uint32_t start_tick;
    while (us > 1000) {
        // check if interrupts are disabled
        if(__get_PRIMASK())
           return; // if not just return
        start_tick=SysTick->VAL;  // wait for SysTick->VAL to  RESET
        while (SysTick->VAL < start_tick) {}
        us -= us_until_next_tick;
        us_until_next_tick = 1000;
    }
    if(us&&(us < us_until_next_tick)){
        while (SysTick->VAL > ((us_until_next_tick - us) * ticks_per_us)) {}
    }
    else {
        start_tick=SysTick->VAL;  // wait for SysTick->VAL to  RESET
        while (SysTick->VAL < start_tick) {}
        us -= us_until_next_tick;
        if(us){
            while (SysTick->VAL > ((1000 - us) * ticks_per_us)) {}
        }
    }
}

// us counts down!
void current_tick(uint64_t* ms, uint32_t* us_until_ms) {
    uint32_t ticks_per_us = common_hal_mcu_processor_get_frequency() / 1000 / 1000;
    *ms = ticks_ms;
    *us_until_ms = SysTick->VAL / ticks_per_us;
}

void wait_until(uint64_t ms, uint32_t us_until_ms) {
    uint32_t ticks_per_us = common_hal_mcu_processor_get_frequency() / 1000 / 1000;
    while(ticks_ms <= ms && SysTick->VAL / ticks_per_us >= us_until_ms) {}
}