hwa/st/stm32/examples/02-1-f1-clocks/main.c

This program blinks a LED after it has configured the system clock to use the PLL driven by the HSE.

main.c

 
/*  This file is part of the HWA project.
 *  Copyright (c) 2017 Christophe Duparquet.
 *  All rights reserved. Read LICENSE.TXT for details.
 */
 
#include BOARD_H
 
#define SYSHZ           (36*1000*1000)  // Desired frequency for the SYSCLK signal
#define AHBHZ           (9*1000*1000)   // Desired frequency for the core (and systick)
 
#define PERIOD          0.5             // Blinking period
 
 
int main ( )
{
  hwa( begin, reset );
 
  /*  After RESET, the core is clocked at 8 MHz by the HSI RC oscillator.
   *
   *  * Start the high-speed external oscillator.
   *  * Configure the PLL source and multiplier (must be done before it is
   *    enabled).
   *  * Prepare the connection of the sysclk to the pll. The hardware waits for
   *    the clocks to be stable before switching.
   */
  hwa( power, hse, on );
  hwa( configure,  pll,
       input,      hse,
       multiplier, SYSHZ/HW_DEVICE_HSEHZ );
  hwa( connect, sysclk, pll );
  hwa( commit );
 
  /*  Now turn the PLL on and the hardware will use it as sysclk when the PLL is
   *  locked.
   */
  hwa( power, pll, on );
  hwa( commit );
 
  /*  Power the GPIO port
   */
  hwa( power, (LED,port), on );
 
  /*  Configure the GPIO pin
   */
  hwa( configure, LED,
       mode,      digital_output,
       frequency, lowest );
 
  hwa( commit );
 
 
  for(;;) {
    hw( toggle, LED );
    hw_waste_cycles( PERIOD/2 * SYSHZ );
  }
}