# Change Pwm channel

Source: https://forum.modalai.com/topic/585/change-pwm-channel
Category: General Questions (https://forum.modalai.com/category/2/general-questions)
Posted: 2021-12-01 19:33:54 UTC by John Mccarty
Replies: 7 · Views: 1547

## John Mccarty · 2021-12-01 19:33:54 UTC

Hello my flight deck pwm connections is broke.Now I cant use channel 3 it does not recieve any signal from this channel..I want to use channel 6 instead of channel 3.How can i do this can you help me.

## Reply by modaltb (ModalAI staff) · 2021-12-02 04:42:47 UTC

Hi @John-Mccarty ,

I haven't done this myself, but I think it should be possible with some hacking with PX4 mixers:

https://docs.px4.io/v1.12/en/concept/mixing.html

I've stuck to the default quad for everything I've ever done (same as default on your Fligh Deck), but you might be able to override using the SD card?

  https://docs.px4.io/master/en/concept/sd_card_layout.html

## Reply by John Mccarty · 2021-12-02 08:46:01 UTC

Thanks for your fast response I have not much experience in px4 code.I need more details. How do i change it and how do i integrate my changed codes into voxl ? I need help. Thanks again.

## Reply by John Mccarty · 2021-12-06 11:49:21 UTC (in reply to modaltb)

@modaltb I tried what you wrote in your post,it`s work on pixhawk when you change mixers file and override with sdcard but on voxl it does`nt work what is the differences between voxl px4 and pixhawk px4  ?

## Reply by modaltb (ModalAI staff) · 2021-12-06 14:08:27 UTC

Hi @John-Mccarty , 

They 'should' operate the same.  One quick thing to check, there are two SD cards on VOXL-Flight, one accessible by the Yocto Linux side, the other by PX4 FW.  You want to use the bottom right one in this picture for this use case.

https://docs.modalai.com/voxl-flight-datasheet-connectors/

![84156103-2115-4dbc-a706-d62ae04199ac-image.png](https://forum.modalai.com/assets/uploads/files/1638799678573-84156103-2115-4dbc-a706-d62ae04199ac-image.png)

## Reply by John Mccarty · 2021-12-06 14:49:09 UTC

thanks for your fast response I inserted the sd card in the right place as in the picture but it still use default mixers file. I placed the changed mixer file in to /etc/mixers/ directory inside sd card.

## Reply by John Mccarty · 2021-12-07 05:43:14 UTC

It has solved.  The problem was the hardware connection .Now I could change pwm channel with hacking mixers file and overriding with sd card.Thanks for your helping.

## Reply by modaltb (ModalAI staff) · 2021-12-07 14:50:03 UTC

Alright!  Thanks for the update, I'll likely use this post to get some updates to our docs, appreciate it!