Tips/firmwares/marlin/Touch Mi - Marlin-bugfix-1.1.x/Marlin/delay.h

/**
 * Marlin 3D Printer Firmware
 * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
 *
 * Based on Sprinter and grbl.
 * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
 *
 * 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 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

/**
 * AVR busy wait delay Cycles routines:
 *
 *  DELAY_CYCLES(count): Delay execution in cycles
 *  DELAY_NS(count): Delay execution in nanoseconds
 *  DELAY_US(count): Delay execution in microseconds
 */

#ifndef MARLIN_DELAY_H
#define MARLIN_DELAY_H

#define nop() __asm__ __volatile__("nop;\n\t":::)

FORCE_INLINE static void __delay_4cycles(uint8_t cy) {
  __asm__ __volatile__(
    L("1")
    A("dec %[cnt]")
    A("nop")
    A("brne 1b")
    : [cnt] "+r"(cy)  // output: +r means input+output
    :                 // input:
    : "cc"            // clobbers:
  );
}

/* ---------------- Delay in cycles */
FORCE_INLINE static void DELAY_CYCLES(uint16_t x) {

  if (__builtin_constant_p(x)) {
    #define MAXNOPS 4

    if (x <= (MAXNOPS)) {
      switch (x) { case 4: nop(); case 3: nop(); case 2: nop(); case 1: nop(); }
    }
    else {
      const uint32_t rem = (x) % (MAXNOPS);
      switch (rem) { case 3: nop(); case 2: nop(); case 1: nop(); }
      if ((x = (x) / (MAXNOPS)))
        __delay_4cycles(x); // if need more then 4 nop loop is more optimal
    }

    #undef MAXNOPS
  }
  else
    __delay_4cycles(x / 4);
}
#undef nop

/* ---------------- Delay in nanoseconds */
#define DELAY_NS(x) DELAY_CYCLES( (x) * (F_CPU/1000000L) / 1000L )

/* ---------------- Delay in microseconds */
#define DELAY_US(x) DELAY_CYCLES( (x) * (F_CPU/1000000L) )

#endif // MARLIN_DELAY_H