Skip to content

Changed micros() to work in interrupts #1388

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 1 commit into from
Closed
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
44 changes: 37 additions & 7 deletions hardware/arduino/sam/cores/arduino/wiring.c
Original file line number Diff line number Diff line change
Expand Up @@ -28,20 +28,50 @@ uint32_t millis( void )
return GetTickCount() ;
}

// Interrupt-compatible version of micros
// Theory: repeatedly take readings of SysTick counter, millis counter and SysTick interrupt pending flag.
// When it appears that millis counter and pending is stable and SysTick hasn't rolled over, use these
// values to calculate micros. If there is a pending SysTick, add one to the millis counter in the calculation.
uint32_t micros( void )
{
uint32_t ticks ;
uint32_t count ;
uint32_t ticks, ticks2;
uint32_t pend, pend2;
uint32_t count, count2;

ticks2 = SysTick->VAL;
pend2 = !!((SCB->ICSR & SCB_ICSR_PENDSTSET_Msk)||((SCB->SHCSR & SCB_SHCSR_SYSTICKACT_Msk))) ;
count2 = GetTickCount();

SysTick->CTRL;
do {
ticks = SysTick->VAL;
count = GetTickCount();
} while (SysTick->CTRL & SysTick_CTRL_COUNTFLAG_Msk);
ticks=ticks2;
pend=pend2;
count=count2;
ticks2 = SysTick->VAL;
pend2 = !!((SCB->ICSR & SCB_ICSR_PENDSTSET_Msk)||((SCB->SHCSR & SCB_SHCSR_SYSTICKACT_Msk))) ;
count2 = GetTickCount();
} while ((pend != pend2) || (count != count2) || (ticks < ticks2));

return count * 1000 + (SysTick->LOAD + 1 - ticks) / (SystemCoreClock/1000000) ;
return ((count+pend) * 1000) + (((SysTick->LOAD - ticks)*(1048576/(F_CPU/1000000)))>>20) ;
// this is an optimization to turn a runtime division into two compile-time divisions and
// a runtime multiplication and shift, saving a few cycles
}

// original function:
// uint32_t micros( void )
// {
// uint32_t ticks ;
// uint32_t count ;
//
// SysTick->CTRL;
// do {
// ticks = SysTick->VAL;
// count = GetTickCount();
// } while (SysTick->CTRL & SysTick_CTRL_COUNTFLAG_Msk);
//
// return count * 1000 + (SysTick->LOAD + 1 - ticks) / (SystemCoreClock/1000000) ;
// }


void delay( uint32_t ms )
{
uint32_t end = GetTickCount() + ms;
Expand Down