teensy-cores/teensy4/IntervalTimer.cpp

/* Teensyduino Core Library
 * http://www.pjrc.com/teensy/
 * Copyright (c) 2018 PJRC.COM, LLC.
 *
 * 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:
 *
 * 1. The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * 2. If the Software is incorporated into a build system that allows
 * selection among a list of target devices, then similar target
 * devices manufactured by PJRC.COM must be included in the list of
 * target devices and selectable in the same manner.
 *
 * 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 "IntervalTimer.h"
#include "debug/printf.h"

static void dummy_funct(void);
static void pit_isr(void);

#define NUM_CHANNELS 4
static void (*funct_table[4])(void) = {dummy_funct, dummy_funct, dummy_funct, dummy_funct};
uint8_t IntervalTimer::nvic_priorites[4] = {255, 255, 255, 255};


bool IntervalTimer::beginCycles(void (*funct)(), uint32_t cycles)
{
	printf("beginCycles %u\n", cycles);
	if (channel) {
		channel->TCTRL = 0;
		channel->TFLG = 1;
	} else {
		CCM_CCGR1 |= CCM_CCGR1_PIT(CCM_CCGR_ON);
		//__asm__ volatile("nop"); // solves timing problem on Teensy 3.5
		PIT_MCR = 1;
		channel = IMXRT_PIT_CHANNELS;
		while (1) {
			if (channel->TCTRL == 0) break;
			if (++channel >= IMXRT_PIT_CHANNELS + NUM_CHANNELS) {
				channel = NULL;
				return false;
			}
		}
	}
	int index = channel - IMXRT_PIT_CHANNELS;
	funct_table[index] = funct;
	channel->LDVAL = cycles;
	channel->TCTRL = 3;
	nvic_priorites[index] = nvic_priority;
	uint8_t top_priority = 255;
	for (int i=0; i < NUM_CHANNELS; i++) {
		if (top_priority > nvic_priorites[i]) top_priority = nvic_priorites[i];
	}
	attachInterruptVector(IRQ_PIT, &pit_isr);
	NVIC_SET_PRIORITY(IRQ_PIT, top_priority);
	NVIC_ENABLE_IRQ(IRQ_PIT);
	return true;
}


void IntervalTimer::end() {
#if 1
	if (channel) {
		int index = channel - IMXRT_PIT_CHANNELS;
		// TODO: disable IRQ_PIT, but only if all instances ended
		funct_table[index] = dummy_funct;
		channel->TCTRL = 0;
		nvic_priorites[index] = 255;
		uint8_t top_priority = 255;
		for (int i=0; i < NUM_CHANNELS; i++) {
			if (top_priority > nvic_priorites[i]) top_priority = nvic_priorites[i];
		}
		NVIC_SET_PRIORITY(IRQ_PIT, top_priority);
		channel = 0;
	}
#endif
}

//FASTRUN
static void pit_isr()
{
	for (int i=0; i < NUM_CHANNELS; i++) {
		IMXRT_PIT_CHANNEL_t *channel = IMXRT_PIT_CHANNELS + i;
		if (channel->TFLG) {
			channel->TFLG = 1;
			funct_table[i]();
		}
	}
}

static void dummy_funct(void)
{
}