I want to know the execution time of some software. Is there a method to measure the execution time without using a debugger?
Answer
You can measure the approximate software execution time using the hardware timer (TCPWM). Here is the code snippet for "Hello World".
Code 1. Original “Hello World”
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#include <stdio.h>
int main() {
printf("Hello World");
return 0;
}
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To measure software execution time, make the following modifications to the “Hello World” code:
- Add the TCPWM timer start command and the TCPWM timer stop command before and after printf ("Hello World").
Code 2 Adding TCPWM Timer Start and Timer Stop Commands
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#include <stdio.h>
int main() {
// Initialize Clock Divider and TCPWM (For more details, please see Technical Reference Manual)
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// If you need, please Enter Critical section to avoid any interrupt during measurement.
uint32_t saveIntrEnabled = Cy_SysLib_EnterCriticalSection(); // Interrupt Disable & Save Current Status
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// Timer Stop/Clear/Start (Please use INLINE function to reduce software offset like below)
Cy_TCPWM_TriggerStopOrKill_Single(TCPWM0, MY_TCPWM_CNT_NUM); // Timer Stop Command (If Timer is Starting)
Cy_TCPWM_PWM_SetCounter(TCPWM0, MY_TCPWM_CNT_NUM,0); // Timer Counter Clear Command
Cy_TCPWM_TriggerStart_Single(TCPWM0, MY_TCPWM_CNT_NUM); // Timer Start Command
printf("Hello World");
// Timer Stop (Please use INLINE function to reduce software offset like below)
Cy_TCPWM_TriggerStopOrKill_Single(TCPWM0, MY_TCPWM_CNT_NUM); // Timer Stop Command
// Read and Save the counter value
uint32_t TimerCount = Cy_TCPWM_PWM_GetCounter(TCPWM0, MY_TCPWM_CNT_NUM);
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// If you need, restore interrupt status
Cy_SysLib_ExitCriticalSection(saveIntrEnabled); // Interrupt Restore Previous Status
return 0;
}
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2.Then, add a command to read the timer value of the corresponding TCPWM. This timer value counts the number of clocks. Therefore, the software execution time can be calculated as:
Example:
Clock Frequency = 25 MHz, Value of TimerCount = 0x0F98 (0d3992)
( 1/25MHz)x3,992=40nsX3,992=159.680us
To make the measurement time more accurate, take the following measures.
- Increase clock speed.
- Measure the time from starting the counter to stopping it. Then, subtract from the count value. Here is an example:
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#include <stdio.h>
int main() {
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// Timer Stop/Clear/Start (Please use INLINE function to reduce software offset like below)
Cy_TCPWM_TriggerStopOrKill_Single(TCPWM0, MY_TCPWM_CNT_NUM); // Timer Stop Command (If Timer is Starting)
Cy_TCPWM_PWM_SetCounter(TCPWM0, MY_TCPWM_CNT_NUM,0); // Timer Counter Clear Command
Cy_TCPWM_TriggerStart_Single(TCPWM0, MY_TCPWM_CNT_NUM); // Timer Start Command
printf("Hello World");
// Timer Stop (Please use INLINE function to reduce software offset like below)
Cy_TCPWM_TriggerStopOrKill_Single(TCPWM0, MY_TCPWM_CNT_NUM); // Timer Stop Command
// Read and Save the counter value
uint32_t TimerCount = Cy_TCPWM_PWM_GetCounter(TCPWM0, MY_TCPWM_CNT_NUM);
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// Measure the time from starting the counter to stopping
Cy_TCPWM_TriggerStopOrKill_Single(TCPWM0, MY_TCPWM_CNT_NUM); // Timer Stop Command (If Timer is Starting)
Cy_TCPWM_PWM_SetCounter(TCPWM0, MY_TCPWM_CNT_NUM,0); // Timer Counter Clear Command
Cy_TCPWM_TriggerStart_Single(TCPWM0, MY_TCPWM_CNT_NUM); // Timer Start Command
uint32_t SwOffsetCount = Cy_TCPWM_PWM_GetCounter(TCPWM0, MY_TCPWM_CNT_NUM);
uint32_t TimerCountDuringHelloWorld = TimerCount – SwOffsetCount;
return 0;
}
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