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TMS570LS3137: HET and signal amplitude

Kevin Uker
Prodigy 50 points
Part Number: TMS570LS3137

Hello,

I'm reposting an issue that one of my colleagues posted back in July that we have not resolved yet.

Link to his post:  https://e2e.ti.com/support/microcontrollers/hercules/f/312/t/612079

 

In general we are using HET pin 30 to capture a 32Khz signal 3vpp and then using pin 31 to output a High if the signal exceeds the 32Khz.  We are seeing very erratic results (meaning pin 31 does not always go high right at 32Khz) based on small changes in the input frequency amplitude.

 

Even with the amplitude staying the same, after a reset to the MCU, the trigger point is not always detected.

 

We have both pins configured with pull-down resistors for code generation.

 

Any suggestions or feedback would be greatly appreciated.

   

  • 0
    TI__Guru 59540 points
    Hello Kevin,

    In order to prevent confustion and avoid a divergance of discussion topics, we should keep the posts to the original thread. Certainly, there have been some challenges in support due to recent weather events and business travel that have limited the immediate response. Note also that QJ had provided a validated solution that he believed should have provided the answer, but more recently has been stated to still exhibit the behaviors or to be the same as the implemented code. Nonetheless, I have responded on the other thread to your inquiry. In the end, we need to recreate you input signal and insure we are testing apples to apples. Also, a scope plot of the input signal with the corresponding NHET31 action would be helpful so we can see exactly what is happening on the input causing the HET output to be set. There could be a simple explanation for this but to date we need more info to help align on the issue now that we can confirm that the code does not seem to be the root cause.