# What are the values read by the GPIO when floating?

**URL:** <https://forums.developer.nvidia.com/t/what-are-the-values-read-by-the-gpio-when-floating/125883>\
**Category:** Jetson AGX Xavier\
**Tags:** hw, gpio\
**Created:** [June 2, 2020, 3:00pm UTC](https://forums.developer.nvidia.com/t/what-are-the-values-read-by-the-gpio-when-floating/125883 "2020-06-02T15:00:34Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![pwoolvett](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/pwoolvett/32/72473_2.png) [@pwoolvett](https://forums.developer.nvidia.com/u/pwoolvett)\
**Post date:** [June 2, 2020, 3:00pm UTC](https://forums.developer.nvidia.com/t/what-are-the-values-read-by-the-gpio-when-floating/125883/1 "2020-06-02T15:00:34Z")

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Hi

Can you help me with the internal pullup/down configuration for the 40-pin header on the carrier board? I am currently having the following issue _in several jetson devices_:

1. 40-pin expansion header has nothing attached

2. from python, using `Jetson.GPIO`, I setup all pins as inputs:

3. `cat`ing the device tree in `/sys/class/gpio/gpioXXX` shows some values to `0` and others to `1`:

4. For example, both `gpio353` (pin **38** , **I2S\_SDIN** ) and `gpio352` (pin **40** , **I2S\_SDOUT** ) show as 1[MOhm] PD to GND in table **Table 19. Jetson X avierExpansion Header Signal Details**. However, one of them shows `value=1` while the other shows `value=0`

Any help or guidance is appreciated

Extra info:

When defining all specified pins as output with value (`1` or `0`), some pins change their value when setting them as input afterwards. This is not consistent with PU/PD info in mentioned table. In particular:

- Set all to `GPIO.HIGH`, then all as inputs → `gpio428=pin 11` , `gpio429=pin 36` , `gpio257=pin 32` , `gpio256=pin 16` , `gpio249=pin 37` , and `gpio248=pin 33` go back to `0`. The rest remains in `1`

- Set all to `GPIO.LOW`, then all as inputs → `gpio250=pin 31` , `gpio251=pin 29` , `gpio353=pin 38` go back to `1`. The rest remains in `0`

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<div class="post-metadata">

**Author:** ![JerryChang](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/jerrychang/32/14043_2.png) [@JerryChang](https://forums.developer.nvidia.com/u/JerryChang)\
**Post date:** [June 3, 2020, 3:06am UTC](https://forums.developer.nvidia.com/t/what-are-the-values-read-by-the-gpio-when-floating/125883/3 "2020-06-03T03:06:31Z")

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hello pwoolvett,

there’s default configurations, you might also access [pinmux spreadsheets](https://developer.nvidia.com/embedded/downloads#?search=pinmux) through download center for customization,  
thanks

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<div class="post-metadata">

**Author:** ![pwoolvett](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/pwoolvett/32/72473_2.png) [@pwoolvett](https://forums.developer.nvidia.com/u/pwoolvett)\
**Post date:** [June 23, 2020, 2:17pm UTC](https://forums.developer.nvidia.com/t/what-are-the-values-read-by-the-gpio-when-floating/125883/5 "2020-06-23T14:17:11Z")

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I’m not sure what/where to look for the defaults. I’m not trying to customize nor remap…

Related [GPIO pull-down resistors - #9 by WasabiFan](https://forums.developer.nvidia.com/t/gpio-pull-down-resistors/78424/9)