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AM2632: ECAP minimal frequency to read

alex dchk
Prodigy 220 points
Part Number: AM2632

Hello,

currently I have question about minimal frequency of the signal which can be read with SYS_CLK=200MHz. Currently I'm seeing 40hz, as minimal value. If i'm going below, my software not able to read the params of signal. Is it possible to have ability to read signal with 1hz frequency,  via increasing of SYS_CLK ?

  • 0
    TI__Guru**** 197046 points

    Hi Alex,

    Did you get CNTOFF interrupt or this over flow flag set? TSCTR is a 32-bit counter, and it increments per sys clock cycle, wraps around to 0x00000000 when it reaches the maximum value 0xFFFFFFFF. The 32-bit counter is bigger enough to measure a 1Hz PWM signal for sysclk=200MHz. Do you use TI SDK?

  • 0 in reply to QJ Wang
    Prodigy 220 points

    not sure about CNTOFF, yes I'm using TI SDK. I was able to read 1hz frequenсy on the launchpad, but with this micro no. What can be wrong? Code is the same

  • 0 in reply to alex dchk
    TI__Guru**** 197046 points

    I am sorry for the typo. It should be CTROVF (counter overflow). 

    Do you enable the event prescaler? The input signal to ECAP can be prescaled by 2~62. This feature is very useful when the input has very high frequency. If this feature is enabled and prescaler is big, you might not be able to measure the 1Hz signal. 

    The prescaler is defined in ECCTL1[13:9]