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/*

   Precise Delay Functions

   V 0.5, Martin Thomas, 9/2004

   Inspired by the avr-libc's loop-code

*/

#ifndef _delay_h_

#define _delay_h_

#include <inttypes.h>

#include <avr/io.h>

/* delay function for microsec

   4 cpu cycles per loop + 1 cycles(?) overhead

   when a constant is passed. */

static inline void delayloop16(uint16_t count)

{

    asm volatile (  "cp  %A0,__zero_reg__ \n\t"  \

                     "cpc %B0,__zero_reg__ \n\t"  \

                     "breq L_Exit_%=       \n\t"  \

                     "L_LOOP_%=:           \n\t"  \

                     "sbiw %0,1            \n\t"  \

                     "brne L_LOOP_%=       \n\t"  \

                     "L_Exit_%=:           \n\t"  \

                     : "=w" (count)

                     : "0"  (count)

                   );                            

}

// delayloop16(x) eats 4 cycles per x

#define DELAY_US_CONV(us) ((uint16_t)(((((us)*1000L)/(1000000000/F_OSC))-1)/4))

#define delay_us(us)      delayloop16(DELAY_US_CONV(us))

/* delay function for millisec

  (6 cycles per x + 20(?) overhead) */

void delayloop32( uint32_t l); // not inline

#define DELAY_MS_CONV(ms) ( (uint32_t) (ms*(F_OSC/6000L)) ) 

#define delay_ms(ms)  delayloop32(DELAY_MS_CONV(ms))

/* mth 9/04:

   Remark uSeconds:

   Main Oscillator Clock given by F_OSC (makefile) in Hz

   one CPU-Cycle takes 1/F_OSC seconds => 1000000/F_OSC uSeconds

   so: 1 uSecond takes F_OSC/1000000 CPU-Cyles. The following code

   is inspired by the avr-libc delay_loop2 function.

   This it not "that precise" since it takes at least 4 cycles

   but should be o.k. with any parameter (even 0).

   Call function with delayloop(DELAYUS(dt [in uSeconds])).

*/

#endif