/*
 * Copyright (c) 2014-2017, Alex Taradov <alex@taradov.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

//-----------------------------------------------------------------------------
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include "saml22.h"
#include "hal_gpio.h"

//-----------------------------------------------------------------------------
#define PERIOD_FAST     100
#define PERIOD_SLOW     500

HAL_GPIO_PIN(LED,       A, 21)
HAL_GPIO_PIN(BUTTON,    A, 30)
HAL_GPIO_PIN(UART_TX,   A, 22)
HAL_GPIO_PIN(UART_RX,   A, 23)

//-----------------------------------------------------------------------------
static void timer_set_period(uint16_t i)
{
  TC3->COUNT16.CC[0].reg = (F_CPU / 1000ul / 256) * i;
  TC3->COUNT16.COUNT.reg = 0;
}

//-----------------------------------------------------------------------------
void irq_handler_tc3(void)
{
  if (TC3->COUNT16.INTFLAG.reg & TC_INTFLAG_MC(1))
  {
    HAL_GPIO_LED_toggle();
    TC3->COUNT16.INTFLAG.reg = TC_INTFLAG_MC(1);
  }
}

//-----------------------------------------------------------------------------
static void timer_init(void)
{
  MCLK->APBCMASK.reg |= MCLK_APBCMASK_TC3;

  GCLK->PCHCTRL[TC3_GCLK_ID].reg = GCLK_PCHCTRL_GEN(0) | GCLK_PCHCTRL_CHEN;
  while (0 == (GCLK->PCHCTRL[TC3_GCLK_ID].reg & GCLK_PCHCTRL_CHEN));

  TC3->COUNT16.CTRLA.reg = TC_CTRLA_MODE_COUNT16 | TC_CTRLA_PRESCALER(6/*DIV256*/) |
      TC_CTRLA_PRESCSYNC_RESYNC;

  TC3->COUNT16.WAVE.reg = TC_WAVE_WAVEGEN_MFRQ;

  TC3->COUNT16.COUNT.reg = 0;

  timer_set_period(PERIOD_SLOW);

  TC3->COUNT16.CTRLA.reg |= TC_CTRLA_ENABLE;

  TC3->COUNT16.INTENSET.reg = TC_INTENSET_MC(1);
  NVIC_EnableIRQ(TC3_IRQn);
}

//-----------------------------------------------------------------------------
static void uart_init(uint32_t baud)
{
  uint64_t br = (uint64_t)65536 * (F_CPU - 16 * baud) / F_CPU;

  HAL_GPIO_UART_TX_out();
  HAL_GPIO_UART_TX_pmuxen(HAL_GPIO_PMUX_C);
  HAL_GPIO_UART_RX_in();
  HAL_GPIO_UART_RX_pmuxen(HAL_GPIO_PMUX_C);

  MCLK->APBCMASK.reg |= MCLK_APBCMASK_SERCOM0;

  GCLK->PCHCTRL[SERCOM0_GCLK_ID_CORE].reg = GCLK_PCHCTRL_GEN(0) | GCLK_PCHCTRL_CHEN;
  while (0 == (GCLK->PCHCTRL[SERCOM0_GCLK_ID_CORE].reg & GCLK_PCHCTRL_CHEN));

  SERCOM0->USART.CTRLA.reg =
      SERCOM_USART_CTRLA_DORD | SERCOM_USART_CTRLA_MODE(1/*USART_INT_CLK*/) |
      SERCOM_USART_CTRLA_RXPO(3/*PAD3*/) | SERCOM_USART_CTRLA_TXPO(1/*PAD2*/);

  SERCOM0->USART.CTRLB.reg = SERCOM_USART_CTRLB_RXEN | SERCOM_USART_CTRLB_TXEN |
      SERCOM_USART_CTRLB_CHSIZE(0/*8 bits*/);

  SERCOM0->USART.BAUD.reg = (uint16_t)br;

  SERCOM0->USART.CTRLA.reg |= SERCOM_USART_CTRLA_ENABLE;
}

//-----------------------------------------------------------------------------
static void uart_putc(char c)
{
  while (!(SERCOM0->USART.INTFLAG.reg & SERCOM_USART_INTFLAG_DRE));
  SERCOM0->USART.DATA.reg = c;
}

//-----------------------------------------------------------------------------
static void uart_puts(char *s)
{
  while (*s)
    uart_putc(*s++);
}

//-----------------------------------------------------------------------------
static void sys_init(void)
{
  // Switch to 16MHz clock (disable prescaler)
  OSCCTRL->OSC16MCTRL.reg = OSCCTRL_OSC16MCTRL_ENABLE | OSCCTRL_OSC16MCTRL_FSEL_16;

  // Switch to the highest performance level
  PM->INTFLAG.reg = PM_INTFLAG_PLRDY;
  PM->PLCFG.reg = PM_PLCFG_PLSEL_PL2_Val;
  while (!PM->INTFLAG.reg);
}

//-----------------------------------------------------------------------------
int main(void)
{
  uint32_t cnt = 0;
  bool fast = false;

  sys_init();
  timer_init();
  uart_init(115200);

  uart_puts("\r\nHello, world!\r\n");

  HAL_GPIO_LED_out();
  HAL_GPIO_LED_clr();

  HAL_GPIO_BUTTON_in();
  HAL_GPIO_BUTTON_pullup();

  while (1)
  {
    if (HAL_GPIO_BUTTON_read())
      cnt = 0;
    else if (cnt < 5001)
      cnt++;

    if (5000 == cnt)
    {
      fast = !fast;
      timer_set_period(fast ? PERIOD_FAST : PERIOD_SLOW);
      uart_putc('.');
    }
  }

  return 0;
}