// 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

  ------------------------------------------------------------------------------

  This firmware currently has these functions:
  - blink the onboard LED C13
  - let an external LED at PB0 fade

  Future features should be:
  - adjust the brightness of the external LED by an incremental encoder
  - enable / disable the light by pressing a push button (included in encoder)
  - offer this functionality via WiFi with an external WiFi-capable board

------------------------------------------------------------------------------
*/


#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);


/* main function

This should give you a brief overview of the control flow. Read the
corresponding function definitions for details about configuration and
implementation.
*/
int main(void)
{
	clock_init();
	gpio_init();
	nvic_init();
	timer_init();

	while(1);  // wait forever
}


/* Clock initialization

This function configures the system clock of the microcontroller (sysclk). The
dynamic configuration allows to execute the program faster (high clock speed)
or to save energy (low clock speed).

Important to notice: On STM32 microcontrollers it is mandatory to enable the
clocks for peripherals and timer / counter units explicitly!
*/
static void clock_init(void)
{
	// set system clock to 72 MHz via external 8 MHz crystal and a PLL
	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);
}


/* Initialization of general purpose inputs and outputs (GPIOs) */
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
	);

	// set initial value to 'on'
	gpio_clear(GPIOC, GPIO13);
	
	// 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
	);
}


/* Nested Vectored Interrupt Controller (NVIC) setup

This function configures NVIC. This way the interrupt triggered by
timer / counter units is enabled explicitly.
*/
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);
}


/* Timer / counter setup

This function configures two timer / counter units (TIM2 and TIM3). TIM2
controls the blinking and fading animation and TIM3 is for the
pulse-width-modulation (PWM) of the external LED.
*/
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
		// TODO: clean the rest of this function ... it is a mess
	*/

	/* 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;
}


/* Timer / counter 2 interrupt service routine

This function is called by the interrupt of timer / counter 2. The function is
not called explicitly in this file but hard-coded in the libopencm3 library.

The purpose of TIM2 is to blink the onboard LED and to decrement the PWM value
resulting in a increment of brightness. Thus this function defines the logic of
the 'animation' shown by the LEDs.
*/
void tim2_isr(void)
{
	// PWM handling
	static uint32_t pwm_value = 0;  // static variable to remember value on next
	                                // function call
	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;
}