// vim: shiftwidth=4 tabstop=4 noexpandtab


/*
  ledcontrol firmware
  Copyright (C) 2021  xengineering

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program 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 General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <https://www.gnu.org/licenses/>.

  Contact: me@xengineering.eu
*/


#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/timer.h>
#include <libopencm3/cm3/nvic.h>


static void clock_init(void);
static void gpio_init(void);
static void nvic_init(void);
static void timer_init(void);

void tim2_isr(void);


int main(void)
{
	clock_init();
	gpio_init();
	nvic_init();
	timer_init();

	while(1);  // wait forever
}


static void clock_init(void)
{
	// set sysclk to 72 MHz via external 8 MHz crystal
	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);

	// enable clocks for GPIO ports B and C
	rcc_periph_clock_enable(RCC_GPIOB);
	rcc_periph_clock_enable(RCC_GPIOC);
	
	// enable clock for timer 2 (blinking)
	rcc_periph_clock_enable(RCC_TIM2);

	// enable clock for timer 3 (PWM)
	rcc_periph_clock_enable(RCC_TIM3);

	// enable clock for alternate functions
	rcc_periph_clock_enable(RCC_AFIO);  // TODO is this necessary?
}


static void gpio_init(void)
{
	// init PC13 onboard LED for blinking
	gpio_set_mode(
		GPIOC,
		GPIO_MODE_OUTPUT_50_MHZ,
		GPIO_CNF_OUTPUT_PUSHPULL,
		GPIO13
	);
	gpio_clear(GPIOC, GPIO13);  // set initial value to 'on'
	
	// setup PB0 (connected to TIM3_CH3) for PWM
	gpio_set_mode(
		GPIOB,
		GPIO_MODE_OUTPUT_50_MHZ,
		GPIO_CNF_OUTPUT_ALTFN_PUSHPULL,
		GPIO_TIM3_CH3
	);
}


static void nvic_init(void)
{
	// enable timer 2 interrupt and set priority
	nvic_enable_irq(NVIC_TIM2_IRQ);
	nvic_set_priority(NVIC_TIM2_IRQ, 1);
}


static void timer_init(void)
{
	// setup timer 2 for blinking
	timer_set_counter(TIM2, 1);
	timer_set_prescaler(TIM2, 1440);
	timer_set_period(TIM2, 50);

	// enable timer / counter 2 and the corresponding interrupt for blinking
	timer_enable_irq(TIM2, TIM_DIER_UIE);
	timer_enable_counter(TIM2);

	/* 
		enable timer / counter 3
	*/

	/* Clock division and mode */
	TIM3_CR1 = TIM_CR1_CKD_CK_INT | TIM_CR1_CMS_EDGE;
	/* Period */
	TIM3_ARR = 65535;
	/* Prescaler */
	TIM3_PSC = 0;
	TIM3_EGR = TIM_EGR_UG;

	/* ---- */
	/* Output compare 3 mode and preload */
	TIM3_CCMR2 |= TIM_CCMR2_OC3M_PWM1 | TIM_CCMR2_OC3PE;

	/* Polarity and state */
	TIM3_CCER |= TIM_CCER_CC3P | TIM_CCER_CC3E;
	//TIM3_CCER |= TIM_CCER_CC3E;

	/* Capture compare value */
	TIM3_CCR3 = 30000;

	/* ---- */
	/* ARR reload enable */
	TIM3_CR1 |= TIM_CR1_ARPE;

	/* Counter enable */
	TIM3_CR1 |= TIM_CR1_CEN;
}


void tim2_isr(void)
{
	// PWM handling
	static uint32_t pwm_value;
	if (pwm_value == 0) {
		pwm_value = 65535;
	}
	else {
		pwm_value -= 20;
	}
	TIM3_CCR3 = pwm_value;

	// toggle blink LED
	static uint32_t counter;
	counter += 1;
	if (counter > 500) {
		gpio_toggle(GPIOC, GPIO13);
		counter = 0;
	}

	// clear interrrupt flag
	TIM_SR(TIM2) &= ~TIM_SR_UIF;
}