/*-------------------------------------------------------------------------------------------------------------------------------------------
 * delay.c - delay functions
 *
 * Copyright (c) 2014-2026 Frank Meyer - frank(at)uclock.de
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *-------------------------------------------------------------------------------------------------------------------------------------------
 */
#include <stdint.h>
#include "delay.h"

uint32_t             delay_ticks_per_usec;

void SysTick_Handler(void);                                                     // keep compiler happy

/*-------------------------------------------------------------------------------------------------------------------------------------------
 * SysTick_Handler() - decrement delay_counter
 *-------------------------------------------------------------------------------------------------------------------------------------------
 */
void
SysTick_Handler(void)
{
   // SysTick ISR needed because SysTick is running for delay functionality
}

/*-------------------------------------------------------------------------------------------------------------------------------------------
 * delay_usec() - delay n microseconds (usec)
 *-------------------------------------------------------------------------------------------------------------------------------------------
 */
void
delay_usec (uint32_t usec)
{
   uint32_t t0 = SysTick->VAL;
   uint32_t ticks = (usec * delay_ticks_per_usec);

   while(1)
   {
      uint32_t dt = (t0 - SysTick->VAL) & 0x00FFFFFF;    // note: SysTick counter is 24 bit
      if (dt > ticks) break;
   }
}

/*-------------------------------------------------------------------------------------------------------------------------------------------
 * delay_msec() - delay n milliseconds (msec)
 *-------------------------------------------------------------------------------------------------------------------------------------------
 */
void
delay_msec (uint32_t msec)
{
   while (msec--)
   {
       delay_usec (1000);
   }
}

/*-------------------------------------------------------------------------------------------------------------------------------------------
 * delay_msec() - delay n seconds (sec)
 *-------------------------------------------------------------------------------------------------------------------------------------------
 */
void
delay_sec (uint32_t sec)
{
    while (sec--)
    {
        delay_msec (1000);
    }
}

/*-------------------------------------------------------------------------------------------------------------------------------------------
 * delay_init() - init delay functions
 *-------------------------------------------------------------------------------------------------------------------------------------------
 */
void
delay_init (void)
{
    SysTick_Config (SysTick_LOAD_RELOAD_Msk);               // use free running 24 bit timer
    delay_ticks_per_usec = SystemCoreClock / 1000000;       // number of timer ticks for 1 usec
}