RTOS/TM4C1292NCPDT: Timer period

Hi,

I want to start the timer from a function in my program. I don't want to do anything when timeout occurs. I want a timer which is having a period of 1us and I need to read the timer count. I just want to get the time in microseconds after the timer starts.

Thanks

Sandra

Thank you Ralph.

Regards

Sandra

Hello Ralph Jacobi,

I believe setting the period to "1" will not give the timer register count will increment in 1 usec interval. i want to timer need to be started and there after timer register value should get increment by 1 usec interval. so that i can read the timer register by using Timer_getCount() for getting the values in 1 usec increment. Please suggest what is the typical configuration required to achieve this?

Regards

Bala

Have you considered using Timestamp_get64() and then converting the result into microseconds using Timestamp_getFreq() to determine the units of the value returned in Timestamp_get64()?

Types_FreqHz freq;
Types_Timestamp64 time;
UInt64 frequency; /* in MHz */
UInt64 timeInUs; /* time in microseconds */

/* do the following once */
Timestamp_getFreq(&freq); /* freq is in Hz */
/* convert freq to MHz */
frequency = ((UInt64)(freq.hi << 32) | (freq.lo) ) / 1000000;

 /* 
  * from then on, simply do the following to obtain the elapsed time since the system started up
 */ 
Timestamp_get64(&time); /* get current timestamp */ 
timeInUs = ((UInt64)(time.hi << 32) | (time.lo) ) / frequency; /* convert to microseconds */

Alan

Hi Alan,

Thanks for the reply.

I am running a seconds counter also in the application. So, while reading microseconds value, I am getting 3232892 us for 11 seconds. For 13 seconds, it was giving 3063887 us. The microseconds value should correspond to seconds value right? How much time it will take to overflow?

I tried by using

ui32Time0 = Timestamp_get32();      // Initial value to find elapsed time

/*Getting current timestamp */

ui32TimeInUs = Timestamp_get32();

ui32TimeInUs = (ui32TimeInUs - ui32Time0) / frequency;      // Frequency got by Timestamp_getFreq() as you suggested

Then I am getting as,

For 34 seconds, 35740198 us  and for 35 seconds, 38538855 us is gotten.

Is this implementation correct? How much time will it take to overflow?

Regards

Sandra

On my Tiva launchpad, the Timestamp frequency is 120MHz. At that rate, the 32 bit timestamp rolls over every 35.79 seconds.

I tried this code on my board and it behaved as expected:

   UInt32 ui32TimeInUs;
   UInt32 ui32Time0 ;
   UInt32 frequency;
   Types_FreqHz freq;

   ui32Time0 = Timestamp_get32();
   Timestamp_getFreq(&freq);
   frequency = freq.lo; /* frequency in Hz */

   ui32TimeInUs = Timestamp_get32();
   ui32TimeInUs = (ui32TimeInUs - ui32Time0) / frequency;

Using the above code, the ui32TimeInUs advanced by 1 every 1 second because the frequency is in Hz.

If you want ui32TimeInUs to truly be in microsecond units, you need to pre-divide the frequency by 1,000,000:

 frequency = frequency / 1000000; /* frequency in MHz */

All subsequent calculations of ui32TimeInUs will then be in units of microseconds and will advance by 1,000,000 every 1 second.

All

Hi Alan,

Thank you for the reply.

When I tried the same code,  the timestamp rolls over by 35 seconds. But the ui32TimeInUs advances by almost 13,00,000 for every 1 second. What may be the reason for this variation?

Thanks

Sandra

Alan,

Thank you very much for the support. I got it.

Thanks

Sandra