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level output in tm4c123 kit

vu thang
Intellectual 390 points
Other Parts Discussed in Thread: DRV8332

hi 

when i use tim4c123 kit , sometime I see V high in pin PC7 GPIO is 1.1V  but I set PC7 is high level (3,3V)

how to fix it 

thankyou

  • 0
    Guru 117855 points

    Indeed 1V1 is too low - follows several suggestions:

    • what's connected to PC7?   Drawing excessive current from a GPIO violates spec & may damage that pin and/or the MCU.
    • have you properly configured PC7 as a GPIO Output?
    • have you measured other GPIO outputs?   This will verify that your SW is proper
    • you note "sometimes" - yet fail to describe (either) the frequency or duration of those 1V1 outputs.   During those "1V1 output {sometimes}) how does your connection to or programming of PC7 differ from the 3V3 (other times?)

    In summary you may be drawing excessive current from PC7, may have improperly configured that pin as a GPIO Output or may not be measuring properly...

  • 0 in reply to cb1_mobile
    Intellectual 390 points
    Hi
    Set GPIO ouput is common,
    it is usualy = 3.3 V in high logic
    but sometime i don't understand it =1,1V in high logic if I use configure GPIOouput funtion
    but when I pull down and configure ouput , it's alway work exacly.
    i connected PC7 to pin RA drv8332 from TI , I see no wrong here
    thankyou
  • 0 in reply to vu thang
    Guru 117855 points

    What is the status (voltage measurement at PC7) when DISCONNECTED from ALL external devices?   If level returns to ~3V3 the GPIO appears ok - you are simply asking it to supply current beyond its rating.   (the configure output API function enables you to set different, output current levels.)

    My firm does not use vendor's DRV as they are  too low in output current for our applications.   (so you must check - you report "seeing no wrong" but fail to report what, where, how you viewed!)   Thus your,  "seeing" - minus any description and/or justification - is not at all convincing...

    You must review the "input current and voltage requirements" of your DRVx - to insure the (relatively weak) MCU GPIO is proper.

    It is always possible that you've (neglected) and/or not adequately tied ground together between DRVx & your MCU board.

  • 0 in reply to cb1_mobile
    Intellectual 390 points
    Vout=1,1V and when I press reset button in kit , Vout=3,3V
    thankyou
  • 0 in reply to vu thang
    TI__Guru**** 244410 points
    Hello Vu

    And if you disconnect the DRV8332 from the device does it show 3.3V?

    Regards
    Amit
  • 0 in reply to cb1_mobile
    Guru 47900 points

    cb1_mobile said:
    What is the status (voltage measurement at PC7) when DISCONNECTED from ALL external devices?

    Perhaps you'll have better luck.   (as we've TWICE now asked the identical question...)

  • 0 in reply to cb1
    TI__Guru**** 244410 points
    Hello cb1

    Another thought that came was could there be a latch up, due to signal noise? I have seen 1.1V on the IO when a high slew rate signal is applied, may be in this case noise pulse!!

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Guru 117855 points

    Hi Amit,

    We'd learn far more if poster would replace his connection to the motor drive w/simple resistive loads.  (w/in spec of the MCU)

    A 330Ω R connected between poster's PC7 & ground (10mA when output is on-high) should prove a good test.

    Motor drives and common (and appropriate) ground connections often over-challenge.

    That pin may be oscillating as well - we're not (really) told "how" poster measured his 1V1.