• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 79 subscribers
  • Views 232 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.

PxOUT changes current drawn by system when port is configured as input without pull up/down

Piergiuseppe Tundo
Genius 3155 points
Other Parts Discussed in Thread: MSP430F5438A

Hi all.

I'm facing a very strange behavior using a MSP430F5438A.

I have set P5.5 and P5.6 as GPIO inputs without pull up/down, say:

P5SEL &= ~(BIT5|BIT6);
P5DIR &= ~(BIT5|BIT6);
P5REN &= ~(BIT5|BIT6);

Then, simply moving from:

P5OUT &= ~(BIT5|BIT6);

to:

P5OUT |= (BIT5|BIT6);

the current drawn by full system decreases by 100 uA (from 280 to 180 uA in LPM3 running from XT1).

Has anyone ever seen something like this or has a plausible explanation?


Thank you in advance.

Regards,

Peppe


  • 0
    TI__Mastermind 22685 points

    Peppe,

    Are these unused pins that are floating?  If so, you should follow the Connection of Unused Pins section of the F5xx Users Guide Section 1.6.  For unused GPIO pins, it says to configure as outputs.

    The reason is that when the pin is an input and it is floating, it could cause weird behavior on the schmitt trigger on the input to the GPIO.  This can lead to excessive current draw, usually around 100uA.

    Mike

  • 0 in reply to Mike Pridgen
    Genius 3155 points

    Mike,

    thank you for your prompt answer.

    I know about current wasted from floating pins, said pins are not floating and other floating pins are terminated in firmware as suggested (ouput low).

    Regards,

    Peppe

**Attention** This is a public forum