Pandaboard ES GPIO Strange Behaviour !!

Khaled Saleh

hello everyone,,

I'm working on a project using pandaboard es (OMAP4460) where i have to use one of the GPIO's as an output, but when i measure the values on any GPIO of the J3 expansion header, it gives me always 1.8 V even if, i didn't export this GPIO pin and the most strange also even if, this pin i configure it as input, IT STILL GIVES ME 1.8V, i tried to cat the value of this pin it gives me 0 but when measuring this pin with MM it gives 1.8V , and I also tried the MUX register for every gpio's pin and i make sure that's they are in mode 3 and are output_pin but still the pins give me 1.8 V !!?

I'm using ubuntu 12.04 pre-installed server image with u-boot as the bootloader,

it would be grateful, if anyone could help me with this issue !!

thanks in advance

over 12 years ago

0 Israel Cepeda over 12 years ago

TI__Expert 5515 points

Hi Saleh,

The 1.8v is because OMAP4460 works with that voltage (look here for the DC Characteristics http://www.ti.com/product/omap4460). Also in the input you see that voltage in because it is like an open circuit or to the air, so it might be possible to read 0 or 1 if you don't tie to the voltage to get the correct logical level, ie a pull-up resistor to 1.8v pin or to ground to get 1 or 0 respectively.

0 Khaled Saleh over 12 years ago in reply to Israel Cepeda

Prodigy 30 points

Thanks Mr.Cepeda for your reply
But, what I have to do now to be capable of using GPIO pins as an output , I can't change the value of the voltage appears on these GPIO's from "/sys/class/gpio/gpioxx/" dir !!?

0 Israel Cepeda over 12 years ago in reply to Khaled Saleh

TI__Expert 5515 points

If by change voltage you mean change the levels for logical 0 or 1, then yes.

Look at this page: http://omapedia.org/wiki/GPIO

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Pandaboard ES GPIO Strange Behaviour !!