Created
August 4, 2022 14:42
-
-
Save mintisan/c6303012ecfaf5355b7aba1ab02ca1a9 to your computer and use it in GitHub Desktop.
[time measure on cortex-m4 platform] #MCU
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
// https://stackoverflow.com/questions/13379220/generating-nanosecond-delay-in-c-on-stm32 | |
uint32_t m_nStart; //DEBUG Stopwatch start cycle counter value | |
uint32_t m_nStop; //DEBUG Stopwatch stop cycle counter value | |
#define DEMCR_TRCENA 0x01000000 | |
/* Core Debug registers */ | |
#define DEMCR (*((volatile uint32_t *)0xE000EDFC)) | |
#define DWT_CTRL (*(volatile uint32_t *)0xE0001000) | |
#define CYCCNTENA (1<<0) | |
#define DWT_CYCCNT ((volatile uint32_t *)0xE0001004) | |
#define CPU_CYCLES *DWT_CYCCNT | |
#define CLK_SPEED 168000000 // EXAMPLE for CortexM4, EDIT as needed | |
#define STOPWATCH_START { m_nStart = *((volatile unsigned int *)0xE0001004);} | |
#define STOPWATCH_STOP { m_nStop = *((volatile unsigned int *)0xE0001004);} | |
static inline void stopwatch_reset(void) | |
{ | |
/* Enable DWT */ | |
DEMCR |= DEMCR_TRCENA; | |
*DWT_CYCCNT = 0; | |
/* Enable CPU cycle counter */ | |
DWT_CTRL |= CYCCNTENA; | |
} | |
static inline uint32_t stopwatch_getticks() | |
{ | |
return CPU_CYCLES; | |
} | |
static inline void stopwatch_delay(uint32_t ticks) | |
{ | |
uint32_t end_ticks = ticks + stopwatch_getticks(); | |
while(1) | |
{ | |
if (stopwatch_getticks() >= end_ticks) | |
break; | |
} | |
} | |
uint32_t CalcNanosecondsFromStopwatch(uint32_t nStart, uint32_t nStop) | |
{ | |
uint32_t nDiffTicks; | |
uint32_t nSystemCoreTicksPerMicrosec; | |
// Convert (clk speed per sec) to (clk speed per microsec) | |
nSystemCoreTicksPerMicrosec = CLK_SPEED / 1000000; | |
// Elapsed ticks | |
nDiffTicks = nStop - nStart; | |
// Elapsed nanosec = 1000 * (ticks-elapsed / clock-ticks in a microsec) | |
return 1000 * nDiffTicks / nSystemCoreTicksPerMicrosec; | |
} | |
void main(void) | |
{ | |
int timeDiff = 0; | |
stopwatch_reset(); | |
// ============================================= | |
// Example: use a delay, and measure how long it took | |
STOPWATCH_START; | |
stopwatch_delay(168000); // 168k ticks is 1ms for 168MHz core | |
STOPWATCH_STOP; | |
timeDiff = CalcNanosecondsFromStopwatch(m_nStart, m_nStop); | |
printf("My delay measured to be %d nanoseconds\n", timeDiff); | |
// ============================================= | |
// Example: measure function duration in nanosec | |
STOPWATCH_START; | |
// run_my_function() => do something here | |
STOPWATCH_STOP; | |
timeDiff = CalcNanosecondsFromStopwatch(m_nStart, m_nStop); | |
printf("My function took %d nanoseconds\n", timeDiff); | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment