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TMS320F280049: Precise frequency measurement with HRCAP

Michael9q
Intellectual 565 points
Part Number: TMS320F280049
Other Parts Discussed in Thread: C2000WARE

Hello there,

I found TMS320F280049 group and even more powerful MSP430FR604x which seem as very good candidates for precise frequency measurement rather than regular MCUs which are slow (nanosecond resolution). I would like to hear your opinion to this measurement requirements.

I need to measure frequency ranging 1-2 MHz of a square signal with averaging over the period of 50 usec.

time measurement resolution: <1ns 

period of one measurement: 50 usec

I need to measure frequency from number of edges of input square wave signal during this period (50 usec). 

I would like to use HRCAP TMS320F280049 as described:

7.11.2 High-Resolution Capture Submodule (HRCAP6–HRCAP7)

The device contains up to two high-resolution capture (HRCAP) submodules. The HRCAP submodule measures the difference, in time, between pulses asynchronously to the system clock. This submodule is new to the eCAP Type 1 module, and features many enhancements over the Type 0 HRCAP module. Applications for the HRCAP include:

• High-resolution period and duty-cycle measurements of pulse train cycles

• Pulse-width capture in either non-high-resolution or high-resolution modes

or 

I would use MSP430FR604x as described: High-precision time measurement resolution

Q1: Can TMS320F280049 / MSP430FR604x  be used for such measurements?

Q2: Is there any working example for similar pulse signal measurements?

Q3: How does HRCAP for TMS320F2XXXXX measurement method works?

Q4: How does MSP430FR604x measurement method works?

Thank you for any help.

Best regards,

Michael

  • 0
    TI__Mastermind 28275 points

    Hi Michael,

    Responses below for the C2000 device:

    Q1: The HRCAP on the F28004x device requires a minimum pulse of 110ns which works out to about a 9MHz signal so will not work for your 1MHz signal.

    Q2: Yes, we have ECAP examples in C2000Ware.

    Q3: For explanation on how the HRCAP works, please read through the HRCAP chapter in the F28004x TRM.

    Q4: Please post your questions about the MSP device on their forum as they will be best equipped to help you there.

    Let us know if you have anymore questions.

  • 0 in reply to Frank Ankapong
    Intellectual 565 points

    Hi Frank,

    I see. So to use HRCAP I would have to increase square wave form to at least 9 MHz or higher?

    Thank you,

    Michael 

  • +1 in reply to Michael9q
    TI__Mastermind 28275 points

    Hi Michael,

    Yes, that is correct. It's the trade-off for the higher resolution of the HRCAP. If you don't absolutely need <1ns precision, you can use our F2838x devices that run at 200MHz. This would give you 5ns precision with the regular ECAP and still enable you to measure your 1MHz signal.