# GPIO missing in /sys/class/gpio

Source: https://forum.modalai.com/topic/4723/gpio-missing-in-sys-class-gpio
Category: VOXL 2 and VOXL 2 Mini (https://forum.modalai.com/category/26/voxl-2-and-voxl-2-mini)
Tags: voxl-2-mini
Posted: 2025-09-02 20:49:23 UTC by psafi
Replies: 5 · Views: 1691

## psafi · 2025-09-02 20:49:23 UTC

I'm trying to connect a serial device to J19 (Pin10, 11) 

```
voxl-gpio read 179 
ERROR:   Failed to open path /sys/class/gpio/gpio1279/value
```

I don't see GPIO 178 and 179 on my system:
![3de32c5d-542b-49b3-8652-c4536fc502e6-image.png](https://forum.modalai.com/assets/uploads/files/1756845528997-3de32c5d-542b-49b3-8652-c4536fc502e6-image.png)

## Reply by psafi · 2025-09-02 22:23:19 UTC

@psafi I was able to use the info in the link below to enable the GPIO pin

https://forum.modalai.com/post/3656

## Reply by Alex Kushleyev (ModalAI staff) · 2025-09-02 22:45:58 UTC (in reply to psafi)

@psafi , before calling `voxl-gpio read`, you need to enable the pin by setting it to input or output. Please check `voxl-gpio -h`.  (hint: use `voxl-gpio -m` / `voxl-gpio mode`)

Alex

## Reply by psafi · 2025-09-04 00:51:20 UTC (in reply to Alex Kushleyev)

@Alex-Kushleyev Thank you!
I understand these ports are intended for RC input and QUP7 is connected directly to the DSP. I am considering these ports to connect a SiK radio (data format can be raw or mavlink). I want to make information coming through the radio available to ROS and PX4 at the same time. Can I use this port at all for application running on linux or is this only available to voxl-px4?

## Reply by psafi · 2025-09-04 01:18:15 UTC (in reply to psafi)

@psafi said in [GPIO missing in /sys/class/gpio](/post/23678):
> @Alex-Kushleyev Thank you!
> I understand these ports are intended for RC input and QUP7 is connected directly to the DSP. I am considering these ports to connect a SiK radio (data format can be raw or mavlink). I want to make information coming through the radio available to ROS and PX4 at the same time. Can I use this port at all for application running on linux or is this only available to voxl-px4?

I am already using the External UART (J10) for another MAVLink device (optical flow sensor board) which is currently configured and working with PX4 (I don't need to intercept that one on the linux side). Would it be possible to connect my serial radio to J10 and switch my optical flow to J19 (and configure PX4 to read MAVLink from J19-10,11)?

## Reply by Eric Katzfey (ModalAI staff) · 2025-09-04 19:27:53 UTC (in reply to psafi)

@psafi Unfortunately, the Mavlink module is not available on the DSP side. We tried it in the past and there were a lot of issues so we only have it on the apps side. You are welcome to try to add it into the DSP side and see how it goes.