• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 31 subscribers
  • Views 484 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Change threshold value for edge detection nhet

David Sabol
Genius 4850 points
Other Parts Discussed in Thread: HALCOGEN, TMS570LS0332

Hi,

I am using the TMS570LS0332 with Halcogen 4.4 and CCS6.1.  I use the HET module to detect edges to monitor an incoming PWM signal.  The signals that are coming in are very noisy (the electrical guys are working on it).  But they are noisy enough that they are falsely tripping the edge detection.

 

Is there a way to configure the threshold that will cause the edge detector to trip?  So for instance it can be configured when going low to high to trip at 3.5 or 4 V.

 

What is the default / current threshold?

 

Is there any filtering done, or can turned on, for input signals into the HET module?

This is a very urgent issue for me to solve, so any help is greatly appreciated.

Thanks,

David

  • 0
    TI__Guru 68950 points

    David,

    You can't change the trip point. The buffer is fixed, 3.3V LVTTL type - and you can see VIH, VIL in the datasheet. There should be a few hundred mV of hysteresis but we don't spec it.

    The HET has input filtering but it's done in time not voltage. It will suppress any pulse shorter than a specified duration.
    There is one time setting for all pins, but you can bypass this filter on pins that are 'clean' (selectable pin by pin).

    Please see the "Suppression Filter" section in the TRM www.ti.com/.../spnu515b.pdf

    EDIT:  Regarding "high to trip at 3.5 or 4 V".  I should have commented on this - the IO are 3.3V and not 5V tolerant:   

    On the 1224 you can run the ADC at 5V and those are the only 5V tolerant inputs - nothing you can route to HET directly.   On the 0332 this isn't an option since the ADC is a 3.3V only ADC on those parts. 

    Sorry I sent you the link to the 1224 but you should find similar informaiton in the TRM for the 0332.

  • 0 in reply to Anthony F. Seely
    Genius 4850 points
    Thanks! I just found that section as I saw your post. It looks like this will fix the issue.

    I appreciate the help.

    David
  • 0 in reply to David Sabol
    TI__Guru 68950 points
    Super - and Sunil just corrected me - the datasheet does spec 180mV of Hysterisis. I just missed it.
    It's in the table w. VIL,VIH.