Subversion Repositories HomeAutomation

Rev

Rev 394 | Blame | Compare with Previous | Last modification | View Log | SVN | RSS feed

  1.  
  2. #ifndef _delay_h_
  3. #define _delay_h_
  4.  
  5. #include <inttypes.h>
  6. #include <avr/io.h>
  7.  
  8. /* delay function for microsec
  9.    4 cpu cycles per loop + 1 cycles(?) overhead
  10.    when a constant is passed. */
  11. static inline void delayloop16(uint16_t count)
  12. {
  13.     asm volatile (  "cp  %A0,__zero_reg__ \n\t"  \
  14.                      "cpc %B0,__zero_reg__ \n\t"  \
  15.                      "breq L_Exit_%=       \n\t"  \
  16.                      "L_LOOP_%=:           \n\t"  \
  17.                      "sbiw %0,1            \n\t"  \
  18.                      "brne L_LOOP_%=       \n\t"  \
  19.                      "L_Exit_%=:           \n\t"  \
  20.                      : "=w" (count)
  21.                      : "0"  (count)
  22.                    );                            
  23. }
  24. // delayloop16(x) eats 4 cycles per x
  25. #define DELAY_US_CONV(us) ((uint16_t)(((((us)*1000L)/(1000000000/F_CPU))-1)/4))
  26. #define delay_us(us)      delayloop16(DELAY_US_CONV(us))
  27.  
  28. /* delay function for millisec
  29.   (6 cycles per x + 20(?) overhead) */
  30. void delayloop32( uint32_t l); // not inline
  31. #define DELAY_MS_CONV(ms) ( (uint32_t) (ms*(F_CPU/6000L)) )
  32. #define delay_ms(ms)  delayloop32(DELAY_MS_CONV(ms))
  33.  
  34. /* mth 9/04:
  35.    Remark uSeconds:
  36.    Main Oscillator Clock given by F_CPU (makefile) in Hz
  37.    one CPU-Cycle takes 1/F_CPU seconds => 1000000/F_CPU uSeconds
  38.    so: 1 uSecond takes F_CPU/1000000 CPU-Cyles. The following code
  39.    is inspired by the avr-libc delay_loop2 function.
  40.    This it not "that precise" since it takes at least 4 cycles
  41.    but should be o.k. with any parameter (even 0).
  42.    Call function with delayloop(DELAYUS(dt [in uSeconds])).
  43. */
  44.  
  45. #endif
  46.