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AM4376: Question for eQEP module.

Denny%20Yang99373
Expert 3805 points
Part Number: AM4376

Hi all,

I have some questions regarding to the eQEP module per Sitara AM4376. The document I referred to is

 

For my application, only QEPA and QEPB signals are used.

So for Quadrature Count Mode,

 

I want to use Table 20-115, the truth table

to interpret Figure 20-136

 

 

Then,

1, QDIR=’1’ means UP in truth table?

2, ‘+1’ means increment and ‘-1’ means decrement in truth table?

3, take QCLK 1, 2, 3 for example(marked in read in above screen short-cut), then according to the truth table, I can get such excel sheet

Previous Edge

Present Edge

QDIR

QPOSCNT

QA↑

QB↑

Up

Increment

QB↑

QA↓

Up

Decrement

QA↓

QB↑

Down

Decrement

 

I supposed that the row marked in red there should be UP/Increment. And ‘Down/Decrement’ = ‘UP/increment’ ??

 

The truth table just seems wrong to me.

 

Could you please help?

thanks!

Denny

  • 0
    TI__Mastermind 22893 points

    Hey Denny,

    Thank you for your patience, upon review, you are correct, this truth table is incorrect in the documentation. A bug will be filed for correction.

    Until the docs are updated please use the table below which matches your description.

    Let me know if you any further questions, 

    Best Regards,

  • 0 in reply to Fleenor
    Prodigy 120 points

    Hello, Fleenor,

    Actually Denny is helping me posting the questions.

    and I do have one more.

     is ' Up increment' = 'Down decrement'?

    and how to interpret below waveforms exactly? the result according to the truth table you provide still can't match my real case.

    Steven

  • 0 in reply to Steven.Guo
    TI__Mastermind 22893 points

    Yes,

    QDIR:UP = QPOSCNT:Increment

    QDIR:DOWN = QPOSCNT:Decrement

    I would need more background on the waveform you provided to provide valid feedback. Is there a clock signal? What does the P5_HW, M_HW2A, and M_HW2B signals represent? 

  • 0 in reply to Fleenor
    Prodigy 120 points

    Hello, Fleenor,

    You can ignore the signal P5_HW. M_HW2A represents QEPA and M_HW2B represents QEPB. there are no corresponding signals to Index or strobe for my application.

    The eQEP functionality is fully on before the 1st edge found on M_HW2A.

    I made a sketch according to your truth table. Somehow it seems not match my system software interpretation to the waveforms, 'one digit bit decrease(or one bit increase in reverse direction)'

    B.R.

    Steven

  • 0 in reply to Steven.Guo
    TI__Mastermind 22893 points

    Hello Steven,

    Please see diagram below that used the EQEP State Machine to decode the EQEP Counter results based on state changes of your sample signal.