text: /* 
   * The MIT License (MIT)
   *
   * Copyright (c) 2019 Ha Thach (tinyusb.org)
   *
   * 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:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * 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.
   *
   * This file is part of the TinyUSB stack.
   */
  
  #include "bsp/board.h"
  
  #include "sam.h"
  #include "hal/include/hal_gpio.h"
  #include "hal/include/hal_init.h"
  #include "hri/hri_nvmctrl_d21.h"
  
  #include "hpl/gclk/hpl_gclk_base.h"
  #include "hpl_pm_config.h"
  #include "hpl/pm/hpl_pm_base.h"
  
  //--------------------------------------------------------------------+
  // MACRO TYPEDEF CONSTANT ENUM DECLARATION
  //--------------------------------------------------------------------+
  #define LED_PIN      17
  #define BUTTON_PIN   14 // pin D5
  
  /* Referenced GCLKs, should be initialized firstly */
  #define _GCLK_INIT_1ST (1 << 0 | 1 << 1)
  
  /* Not referenced GCLKs, initialized last */
  #define _GCLK_INIT_LAST (~_GCLK_INIT_1ST)
  
  void board_init(void)
  {
    // Clock init ( follow hpl_init.c )
    hri_nvmctrl_set_CTRLB_RWS_bf(NVMCTRL, 2);
  
    _pm_init();
    _sysctrl_init_sources();
  #if _GCLK_INIT_1ST
    _gclk_init_generators_by_fref(_GCLK_INIT_1ST);
  #endif
    _sysctrl_init_referenced_generators();
    _gclk_init_generators_by_fref(_GCLK_INIT_LAST);
  
    // Led init
    gpio_set_pin_direction(LED_PIN, GPIO_DIRECTION_OUT);
    gpio_set_pin_level(LED_PIN, 0);
  
    // Button init
    gpio_set_pin_direction(BUTTON_PIN, GPIO_DIRECTION_IN);
    gpio_set_pin_pull_mode(BUTTON_PIN, GPIO_PULL_DOWN);
  
  #if CFG_TUSB_OS  == OPT_OS_NONE
    // 1ms tick timer (samd SystemCoreClock may not correct)
    SysTick_Config(CONF_CPU_FREQUENCY / 1000);
  #endif
  
    /* USB Clock init
     * The USB module requires a GCLK_USB of 48 MHz ~ 0.25% clock
     * for low speed and full speed operation. */
    _pm_enable_bus_clock(PM_BUS_APBB, USB);
    _pm_enable_bus_clock(PM_BUS_AHB, USB);
    _gclk_enable_channel(USB_GCLK_ID, GCLK_CLKCTRL_GEN_GCLK0_Val);
  
    // USB Pin Init
    gpio_set_pin_direction(PIN_PA24, GPIO_DIRECTION_OUT);
    gpio_set_pin_level(PIN_PA24, false);
    gpio_set_pin_pull_mode(PIN_PA24, GPIO_PULL_OFF);
    gpio_set_pin_direction(PIN_PA25, GPIO_DIRECTION_OUT);
    gpio_set_pin_level(PIN_PA25, false);
    gpio_set_pin_pull_mode(PIN_PA25, GPIO_PULL_OFF);
  
    gpio_set_pin_function(PIN_PA24, PINMUX_PA24G_USB_DM);
    gpio_set_pin_function(PIN_PA25, PINMUX_PA25G_USB_DP);
  
    // Output 500hz PWM on D12 (PA19 - TCC0 WO[3]) so we can validate the GCLK0 clock speed with a Saleae.
    _pm_enable_bus_clock(PM_BUS_APBC, TCC0);
    TCC0->PER.bit.PER = 48000000 / 1000;
    TCC0->CC[3].bit.CC = 48000000 / 2000;
    TCC0->CTRLA.bit.ENABLE = true;
  
    gpio_set_pin_function(PIN_PA19, PINMUX_PA19F_TCC0_WO3);
    _gclk_enable_channel(TCC0_GCLK_ID, GCLK_CLKCTRL_GEN_GCLK0_Val);
  }
  
  //--------------------------------------------------------------------+
  // Board porting API
  //--------------------------------------------------------------------+
  
  void board_led_write(bool state)
  {
    gpio_set_pin_level(LED_PIN, state);
  }
  
  uint32_t board_button_read(void)
  {
    // button is active high
    return gpio_get_pin_level(BUTTON_PIN);
  }
  
  #if CFG_TUSB_OS  == OPT_OS_NONE
  volatile uint32_t system_ticks = 0;
  void SysTick_Handler (void)
  {
    system_ticks++;
  }
  
  uint32_t board_millis(void)
  {
    return system_ticks;
  }
  #endif
  