# Pull up/down on GPIO **URL:** \ **Category:** Octave\ **Created:** [April 22, 2021, 7:34am UTC](https://forum.sierrawireless.com/t/pull-up-down-on-gpio/23503 "2021-04-22T07:34:01Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![romuald](https://avatars.discourse-cdn.com/v4/letter/r/db5fbb/32.png) [@romuald](https://forum.sierrawireless.com/u/romuald)\ **Post date:** [April 22, 2021, 7:34am UTC](https://forum.sierrawireless.com/t/pull-up-down-on-gpio/23503/1 "2021-04-22T07:34:01Z")
I cannot setup the GPIO Input Digital with a pull down / pull up or none. The setting doesn’t appear on UI. ![Capture d’écran 2021-04-22 à 09.24.33](https://us1.discourse-cdn.com/flex025/uploads/sierrawireless/original/2X/b/b9028030a24c4f7db621c5276483465a2eebabc7.jpeg) FX30S Octave - Firmware 3.1.0 Romuald ---
**Author:** ![imorrison](https://avatars.discourse-cdn.com/v4/letter/i/c6cbf5/32.png) [@imorrison](https://forum.sierrawireless.com/u/imorrison)\ **Post date:** [April 22, 2021, 1:19pm UTC](https://forum.sierrawireless.com/t/pull-up-down-on-gpio/23503/2 "2021-04-22T13:19:03Z")
Hi, The IO pins on the rear panel of the FX30 operate differently than those on the IoT slot. The IO1, 2, 3 pins are buffered and protected. They use separate GPIO to control the pull resistors. In the case of IO2, the signal which controls the pull up is EXT\_IO2\_PU. This is documented in the FX30 user guide : [https://source.sierrawireless.com/-/media/support\_downloads/airlink/fastrack/41110030\_fx30-user-guide\_r6.ashx](https://source.sierrawireless.com/-/media/support_downloads/airlink/fastrack/41110030_fx30-user-guide_r6.ashx) Thanks, Ian ---
**Author:** ![romuald](https://avatars.discourse-cdn.com/v4/letter/r/db5fbb/32.png) [@romuald](https://forum.sierrawireless.com/u/romuald)\ **Post date:** [April 23, 2021, 3:21pm UTC](https://forum.sierrawireless.com/t/pull-up-down-on-gpio/23503/3 "2021-04-23T15:21:54Z")
Thank you for your answer. The documentation said that a pull up is connected to the GPIO when EXT\_IO2\_PU = false. Could you confirm when the EXT\_IO2\_PU is true, a internal pull down is connected to the GPIO ? Thank you, Romuald ---
**Author:** ![imorrison](https://avatars.discourse-cdn.com/v4/letter/i/c6cbf5/32.png) [@imorrison](https://forum.sierrawireless.com/u/imorrison)\ **Post date:** [April 23, 2021, 7:59pm UTC](https://forum.sierrawireless.com/t/pull-up-down-on-gpio/23503/4 "2021-04-23T19:59:51Z")
Hi Romuald, I can confirm that setting EXT\_IO2\_PU to **true** will enable the pull up on IO2. This is in line with with Table D-1 or the FX30 User Guide, where the corresponding GPIO must be high (asserted) to enble the pull up. Where did you see the documentation which says “pull up is connected to the GPIO when EXT\_IO2\_PU = false” ? We will correct it. Thanks, Ian ---
**Author:** ![romuald](https://avatars.discourse-cdn.com/v4/letter/r/db5fbb/32.png) [@romuald](https://forum.sierrawireless.com/u/romuald)\ **Post date:** [April 26, 2021, 12:14pm UTC](https://forum.sierrawireless.com/t/pull-up-down-on-gpio/23503/5 "2021-04-26T12:14:09Z")
Hi Ian, Sorry, I was wrong. My configuration is : I didn’t connect anything on IO2. When I set EXT\_IO2\_PU to true (pull up), I detect a false value on EXT\_IO2\_DI. When I set EXT\_IO2\_PU to false, I detect a true value on EXT\_IO2\_DI : is the GPIO connected internally to the ground via a pull down ? If yes, what’s is the impedance of the pull down ? Thanks, Romuald ---
**Author:** ![imorrison](https://avatars.discourse-cdn.com/v4/letter/i/c6cbf5/32.png) [@imorrison](https://forum.sierrawireless.com/u/imorrison)\ **Post date:** [April 26, 2021, 6:49pm UTC](https://forum.sierrawireless.com/t/pull-up-down-on-gpio/23503/6 "2021-04-26T18:49:23Z")
Hi Romuald, Yes. There is an internal pull down network on the input of IO2. Please see the attached sketch. Thanks, Ian ![FX30_IO2_in](https://us1.discourse-cdn.com/flex025/uploads/sierrawireless/original/2X/9/9fff0e1d6a6d405a3af9738039cc644dfbb80041.png) ---
**Author:** ![romuald](https://avatars.discourse-cdn.com/v4/letter/r/db5fbb/32.png) [@romuald](https://forum.sierrawireless.com/u/romuald)\ **Post date:** [April 26, 2021, 6:52pm UTC](https://forum.sierrawireless.com/t/pull-up-down-on-gpio/23503/7 "2021-04-26T18:52:54Z")
Thank you Ian for your detailed answer.