TMS320F28335: Disabling of pull up register not working

B M Mohan

Hi,

I have configured the pins as input, when i disable the pullup, i expect the values of DAT registers to be 0. However i always see '1'. irrespective of PULL UP configuration.

If any one has any clue, it will be of great help.

Thank you

over 7 years ago

0 Rajaravi Krishna Katta over 7 years ago

TI__Expert 6795 points

Hi Mohan,

Please send the details of the GPIO number.

Thanks,
Katta

0 B M Mohan over 7 years ago in reply to Rajaravi Krishna Katta

Expert 1720 points

Thank you Katta for you reply,

Its the same on all GPIO's

I tried on PORT A, when i set it as output all DAT register fills with ZERO, when i make PORT A as input, all DAT's gets filled with ONE.

0 Rajaravi Krishna Katta over 7 years ago in reply to B M Mohan

TI__Expert 6795 points

Hi Mohan,

Could you refer below FAQ

http://processors.wiki.ti.com/index.php/General_Purpose_IO_%28GPIO%29_FAQ_for_C2000#Reset_State

and e2e.ti.com/.../359175

Thanks,
Katta

0 B M Mohan over 7 years ago in reply to Rajaravi Krishna Katta

Expert 1720 points

I did go through this article.. it didnt help much.. as i tried with all combnations, and still see the gpio input status always high

0 Cody Watkins over 7 years ago in reply to B M Mohan

TI__Mastermind 42195 points

Mohan,
The "DAT" registers only take effect if the "DIR" register is configured as an output. Disabling the pull up doesn't mean that the pin value will be 0 by default. It just means that the c2000 device will not attempt to pull a floating pin high.

In input mode the pin will be left floating. It could float up, down, or even somewhere in the middle if there is nothing driving it. Additionally if there is a minor resistive path to VDD then the pin will float to VDD.

Note if something is connected to the pin it also could be pulling it high.

Regards,
Cody

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TMS320F28335: Disabling of pull up register not working