I have the RTC set up to give an interrupt every second, in the interrupt I reset the FTM counter and my software FTM overflow counter and then wait for an input capture. When I get the input capture I print (over USB-CDC) the time in hours, minutes, seconds and then the time to the input capture event in nano-seconds. The FTM is set up to be clocked at 50MHz so the tick is 20nS.
Thus the highest value I would expect to see in my "software" overflow counter before the "seconds" interrupt cleared it, would be 1/(65334 x 20nS) = 762
However I regularly see values over this, can anyone say why this would happen?
Here is the main code created with KSDK 1.3
//turns on seconds interrupt;
RTC_DRV_SetSecsIntCmd(rtcTimer1_IDX, true);
//Turn on the FTM counter in free running mode and enable overflow int
FTM_DRV_CounterStart(flexTimer1_IDX, kCounting_FTM_UP, 0x00, 0xFFFF, true);
//Turn on the FTM0 input capture
FTM_DRV_SetupChnInputCapture(flexTimer1_IDX, kFtmFallingEdge, FTM0_channel_1, input_filter_off);
for(;;){
if (FTM0_Ch1_ICflag == 1 )
{
FTM0_Ch1_ICflag = 0; // clears "input capture" flag set in FTM interrupt routine
cmd_get_datetime(); // prints the current date time
Ch1_nanoseconds_value =(((FTM0_Ch1_timer_overflow_count_store <<16) + FTM0_Ch1_capture_value)*20); // calculates the ns position of pulse this second
PRINTF("capture value%d\r\n", FTM0_Ch1_capture_value);
PRINTF("overflowcount %d\r\n", FTM0_Ch1_timer_overflow_count_store);
PRINTF("overflowcount x 65536 = %d\r\n", (FTM0_Ch1_timer_overflow_count_store<<16));
PRINTF("and %dns\r\n\n",Ch1_nanoseconds_value);
}
}
.....and here is the terminal view, with a couple of examples (second and last) with the overflow count significantly above 762, any thoughts?
Here are the two interrupt routines.
void RTC_Seconds_IRQHandler(void)
{
FTM0_timer_overflow_count= 0; //Resets my timer overflow counter back to zero
FTM_HAL_SetCounter(g_ftmBase[flexTimer1_IDX],0); //Resets the FTM counter back to zero
}
void FTM0_IRQHandler(void)
{
//checking the interrupt flag source and clearing
if(FTM_HAL_HasTimerOverflowed(g_ftmBase[flexTimer1_IDX]))
{
FTM_HAL_ClearTimerOverflow(g_ftmBase[flexTimer1_IDX]);
FTM0_timer_overflow_count++;
}
if(FTM_HAL_HasChnEventOccurred(g_ftmBase[flexTimer1_IDX],CHAN1_IDX))
{
FTM_HAL_ClearChnEventFlag(g_ftmBase[flexTimer1_IDX],CHAN1_IDX);
FTM0_Ch1_timer_overflow_count_store = FTM0_timer_overflow_count;
FTM0_Ch1_capture_value=FTM_HAL_GetChnCountVal(g_ftmBase[flexTimer1_IDX],CHAN1_IDX);
FTM0_Ch1_ICflag = true;
}
}
Thanks!
Hello Ernest,
Please pay attention that , there are five clock configuration you can choose:
if you want use the mode 0, please configure it at here :
then in the FTM component , the clock source you can choose 50MHZ.
In your project , for you chose the mode 4:
we can see in the mode 4, the system clock is 60MHZ, so ....
Hope it helps
Have a great day,
Alice Yang
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Hi Alice, thanks for the insight, that would make sense, but please have a look at my MCG settings, they are set to have the system clock at 50MHz, but for some reason the FTM is saying that the system clock is 60MHz.
Is the FTM overwriting the settings from the clockMAN? Also, I can not seem to be able to change the FTM component inspector to 50MHz.
Hello Ernest,
Please pay attention that , there are five clock configuration you can choose:
if you want use the mode 0, please configure it at here :
then in the FTM component , the clock source you can choose 50MHZ.
In your project , for you chose the mode 4:
we can see in the mode 4, the system clock is 60MHZ, so ....
Hope it helps
Have a great day,
Alice Yang
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------
Hello Jim,
Yes, if you configure the bus clock to 50M, the best value to 48M of USB is configure to 50M.
Hope it helps
Have a great day,
Alice Yang
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------
Hello Ernest,
I have checked your code and test it , from the PE configuration , we can see you configure the
clock source of FTM0 60MHZ,
so we should change this 1/(65334 x 20nS) = 762 to 60MHZ/65334 = 918 .
And from your result , this is no "overflow count" more than 918 , and also in my test , there is neither .
Hope it helps
Have a great day,
Alice Yang
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
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