sifive_Hifive1blink.c

/******************************************************************************
    sifive_Hifive1blink.c
    
    DEVELOPMENT ENVIRONMENT SPECIFICS:
      Firmware developed using Freedom Studio v4.12.0.2019-08-2
      on Windows 10

    ========== RESOURCES ==========
    Freedom E SDK
    
    ========== DESCRIPTION==========
    Using the built-in LED. To test with different pin,
    simply modify the reference pin and connect a standard LED  
    and 100‪Ω resistor between the respective pin and GND.
    
    LICENSE: This code is released under the MIT License (http://opensource.org/licenses/MIT)
  ******************************************************************************/

#include <stdio.h>      //include Serial Library
#include <time.h>       //include Time library (might not need)?
#include <metal/gpio.h> //include GPIO library, https://sifive.github.io/freedom-metal-docs/apiref/gpio.html

//#define builtin_LED 5 //IC's GPIO = 5, pin silkscreen = 13, this line won't work, we need an integer...

//custom write delay function since we do not have one like an Arduino
void delay(int number_of_microseconds) //not actually number of seconds
{

  // Converting time into multiples of a hundred nS
  int hundred_ns = 10 * number_of_microseconds;
  
  // Storing start time
  clock_t start_time = clock();
  
  // looping till required time is not achieved
  while (clock() < start_time + hundred_ns);
  
}//end delay



int main (void) {
  //make instance of GPIO
  struct metal_gpio *led0;

  //Note: The sequence of these commands matter!

  //Get gpio device handle, i.e.) define IC pin here where IC's GPIO = 5, pin silkscreen = 13
  //this is the GPIO device index that is referenced from 0, make sure to check the schematic
  led0 = metal_gpio_get_device(0);

  // quick check to see if we set the metal_gpio up correctly, this was based on the "sifive-welcome.c" example code
  if (led0 == NULL) {
    printf("LED is null.\n");
    return 1;
  }
  //Pins are set when initialized so we must disable it when we use it as an input/output
  metal_gpio_disable_input(led0, 5);

  //Set as gpio as output
  metal_gpio_enable_output(led0, 5);

  //Pins have more than one function, make sure we disconnect anything connected...
  metal_gpio_disable_pinmux(led0, 5);

  //Turn ON pin
  metal_gpio_set_pin(led0, 5, 1);



  while (1) {//loop through, sort of like an Arduino loop()

    //Turn OFF pin
    metal_gpio_set_pin(led0, 5, 0);
    //Use custom "delay" function
    delay(2000000); //2000000 "micro-seconds" ~ 1 second, through experimentation... 
    //Turn ON pin
    metal_gpio_set_pin(led0, 5, 1);
    //Use custom "delay" function
    delay(2000000);

    /***************************************************

    //crude method of "delaying" without messing with the cpu's interrupts...
    for (int i = 0; i < 25000; i++) {
      metal_gpio_set_pin(led0, 5, 0);
    }
    for (int i = 0; i < 25000; i++) {
      metal_gpio_set_pin(led0, 5, 1);
    }

    ***************************************************/
  }

  // return
  return 0;
}//end main