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How to read the external timer counter on the BeagleBone Black?

Jhonny

Hi everyone. I need to measure the frequency with a BeagleBone (400 kHz) and for this I would like to use the BeagleBone timers. How can I read the value of TIMER?
For example, TIMER4 is located in /sys/devices/platform/ocp/48044000.timer/, but l can't find how to read the timer value. 

Are there other ways to measure frequency with a beaglebone? I am new to Beaglebone, so I will be glad to advice and guides

PS: I would like to measure the frequency using timers without installing any additional libraries. But if it is not possible to do this with the help of timers, then please tell me how can such a frequency be measured at all?

I'm using the latest Ubuntu Linux for BeagleBone, kernel 4.

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    Hi,

    Short answer (typing on mobile) maybe not the best answer, you might get better answers from others:

    One option is to dig into the AM3359 datasheet, identify the registers that you need to program and query, and google mmap which can be used to access the registers from user space I.e. your code. Personally that is the route I would take if it were me.

    Another option could be to use the PRU. There is a learning curve however. Given that you suggest there is already a timer that you may be able to use, then I'd put the PRU as a lower preference compared to directly accessing the timer (providing its not used by Linux).

    Your question has insufficient information, for instance its not clear at all why you want to measure 400 kHz. Perhaps it could be divided using external hardware and then you could even do it entirely using existing time functions in C, with some jitter that may not matter - I have no idea because you have not explained your need.

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  • 0

    Hi,

    Short answer (typing on mobile) maybe not the best answer, you might get better answers from others:

    One option is to dig into the AM3359 datasheet, identify the registers that you need to program and query, and google mmap which can be used to access the registers from user space I.e. your code. Personally that is the route I would take if it were me.

    Another option could be to use the PRU. There is a learning curve however. Given that you suggest there is already a timer that you may be able to use, then I'd put the PRU as a lower preference compared to directly accessing the timer (providing its not used by Linux).

    Your question has insufficient information, for instance its not clear at all why you want to measure 400 kHz. Perhaps it could be divided using external hardware and then you could even do it entirely using existing time functions in C, with some jitter that may not matter - I have no idea because you have not explained your need.

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