/*
 * Copyright (c) 2023 Lucas Dietrich <[email protected]>
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <avrtos.h>
#include <avrtos/drivers/usart.h>
#include <avrtos/drivers/timer.h>
#include <avrtos/drivers/gpio.h>
#include <avrtos/drivers/exti.h>

#if defined(__AVR_ATmega2560__)
#	define INT0_PORT GPIOD
#	define INT0_PIN 0u
#elif defined(__AVR_ATmega328P__) || defined(__AVR_ATmega328PB__)
#	define INT0_PORT GPIOD
#	define INT0_PIN 2u
#else
#	error "Unsupported MCU for this example"
#endif 

ISR(TIMER1_COMPA_vect)
{
	static uint8_t i = 0u;

	/* Toggle builtin LED */
	digitalWrite(LED_BUILTIN, i = !i);
}

ISR(INT0_vect)
{
	/* Send a character to USART0 */
	ll_usart_sync_putc(USART0_DEVICE, '!');
}

ISR(USART0_RX_vect)
{
	/* Read data register to clear interrupt flag */
	(void)USART0_DEVICE->UDRn;

	/* Generate a software interrupt */
	gpiol_pin_toggle(INT0_PORT, INT0_PIN);
}

void setup(void)
{
	/* LED initialisation */
	pinMode(LED_BUILTIN, OUTPUT);

	/* UART initialisation */
	const struct usart_config usart_config = {
		.baudrate    = CONFIG_SERIAL_USART_BAUDRATE,
		.receiver    = 1u,
		.transmitter = 1u,
		.mode	     = USART_MODE_ASYNCHRONOUS,
		.parity	     = USART_PARITY_NONE,
		.stopbits    = USART_STOP_BITS_1,
		.databits    = USART_DATA_BITS_8,
		.speed_mode  = USART_SPEED_MODE_NORMAL,
	};
	usart_init(USART0_DEVICE, &usart_config);

	/* Enable USART RX interrupt */
	ll_usart_enable_rx_isr(USART0_DEVICE);

	/* Timer initialisation */
	const struct timer_config timer_config {
		.mode = TIMER_MODE_CTC,
		.prescaler = TIMER_PRESCALER_1024,
		.counter = TIMER_CALC_COUNTER_VALUE(1000000lu, 1024lu),
		.timsk = BIT(OCIEnA),
	};
	timer16_init(TIMER1_DEVICE, &timer_config);

	/* Configure INT0 pin as output to generate a software interrupt */
	gpiol_pin_init(INT0_PORT, INT0_PIN, GPIO_MODE_OUTPUT, GPIO_OUTPUT_DRIVEN_LOW);

	/* Configure INT0 interrupt */
	exti_configure(INT0, ISC_EDGE);
	exti_clear_flag(INT0);
	exti_enable(INT0);

	printf_P(PSTR("Send a character to USART0 to trigger a software interrupt\n"));
}

void loop(void)
{
	// nothing to do, everything is handled by interrupts
	// ...
}