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Make DELAY_NS round up on AVR (#21546)

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This commit is contained in:
Mike La Spina
2021-04-05 16:34:31 -05:00
committed by GitHub
parent e3116eed2e
commit 993609b5aa
2 changed files with 33 additions and 4 deletions
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35
Marlin/src/HAL/shared/Delay.h
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@@ -150,8 +150,37 @@ void calibrate_delay_loop();
#endif
// Delay in nanoseconds
#define DELAY_NS(x) DELAY_CYCLES((x) * ((F_CPU) / 1000000UL) / 1000UL)
/**************************************************************
* Delay in nanoseconds. Requires the F_CPU macro.
* These macros follow avr-libc delay conventions.
*
* For AVR there are three possible operation modes, due to its
* slower clock speeds and thus coarser delay resolution. For
* example, when F_CPU = 16000000 the resolution is 62.5ns.
*
* Round up (default)
* Round up the delay according to the CPU clock resolution.
* e.g., 100 will give a delay of 2 cycles (125ns).
*
* Round down (DELAY_NS_ROUND_DOWN)
* Round down the delay according to the CPU clock resolution.
* e.g., 100 will be rounded down to 1 cycle (62.5ns).
*
* Nearest (DELAY_NS_ROUND_CLOSEST)
* Round the delay to the nearest number of clock cycles.
* e.g., 165 will be rounded up to 3 cycles (187.5ns) because
* it's closer to the requested delay than 2 cycle (125ns).
*/
#ifndef __AVR__
#undef DELAY_NS_ROUND_DOWN
#undef DELAY_NS_ROUND_CLOSEST
#endif
#if ENABLED(DELAY_NS_ROUND_DOWN)
#define DELAY_NS(x) DELAY_CYCLES((x) * ((F_CPU) / 1000000UL) / 1000UL) // floor
#elif ENABLED(DELAY_NS_ROUND_CLOSEST)
#define DELAY_NS(x) DELAY_CYCLES(((x) * ((F_CPU) / 1000000UL) + 500) / 1000UL) // round
#else
#define DELAY_NS(x) DELAY_CYCLES(((x) * ((F_CPU) / 1000000UL) + 999) / 1000UL) // "ceil"
#endif