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MSP430FR6877: Wrong input detection on P1.3

Ted Huh
Intellectual 2460 points
Part Number: MSP430FR6877

Hi Team,

one of my customer using P1.3 as button input. as below.

Because button didn't work in the field, they tested the pin after remove SW2 and C2, and they get this result.

 

R7 Resistor Value

RETURN Pin  Voltage(V)

(P1.3/TA1.2/A3/C3)

Input Value by MSP

1K

2.57

High

5.1K

1.67

Low

10K

1.23

100K

0.22

 

 GPIO output mode works fine. they were able to drive P1.3 normal.

In conclusion, it seems like internal resistance value of P1.3 became about 8k ohm.

How can this happen? could you guess any reason for this?

here is their register settings.


P1DIR &=~ BIT3;   //Input

P1IES |= BIT3;   // Hi->Lo Interrupt

P1IFG &=~ BIT3; // Interrupt flag

P1IE |= BIT3;  // Interrupt Enable


Best Regards,

Ted

  • 0
    TI__Genius 12315 points

    Hi Ted,

    Thanks for your post. There is equivalent resistance on I/Os. I will confirm the equivalent resistance value with our design team later.

    Best Regards,

    If my post helped solve your issue, please click on the  VERIFY ANSWER    button. 

    Winter,

    Search E2E! Your questions may already be answered! 

  • 0 in reply to Winter Yu
    TI__Intellectual 2460 points

    Hi Winter,

    Problem is not that.

    it worked well at first but it changed while it's working.

    Did MSP Team ever had this kind of issue?

    I'm asking why this kind of issue occur and how to prevent this problem.

    of course the equivalent resistance vaule will not be 8k ohm..

    it should be some Mega ohm.

    Regards,

    Ted 

  • 0 in reply to Ted Huh
    TI__Genius 12315 points

    Hi Ted,

    Do you mean using the fixed external pull-up resistor, the voltage of P1.3 will change while working and cause wrong pin input value? If issue is like that, it is more critical value. Thanks for your post. Could you please provide more details:

    • How many chips do you test? Is the issue only found in one chip? 
    • What the development stage of your customer? Design or mass production? 
    • More testing data with fixed pull-up resistor.
    • Remove the external pull-up and change to internal pull-up to test.

    Very appreciate your effort on figure out this issue.

    Best Regards,

    If my post helped solve your issue, please click on the  VERIFY ANSWER    button. 

    Winter,

    Search E2E! Your questions may already be answered! 

  • 0 in reply to Winter Yu
    TI__Intellectual 2460 points

    It's one chip. they built about 10000 units.

    It's field issue. they started MP January this year.

    I think I can get more testing data. However, it seems very clear. why do you need more testing with external resistor?

    I will tell them to test with internal pull up.

    Ted

  • 0 in reply to Ted Huh
    TI__Intellectual 2460 points
    Here is the result for the internal pull up test
    : P1IN bit 3 - low
    voltage of the port : 0.545V
  • 0 in reply to Ted Huh
    TI__Genius 12315 points

    Hi,

    Please help to test more chips. Since I want to determine if it is a comm issue or just a ESD failure of one pin. 

    Best Regards,

    If my post helped solve your issue, please click on the  VERIFY ANSWER    button. 

    Winter,

    Search E2E! Your questions may already be answered! 

  • 0 in reply to Winter Yu
    TI__Intellectual 2460 points
    Hi Winter,

    I will let you know if there is another IC with same problem.

    Ted

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