# M0138 protocol

Source: https://forum.modalai.com/topic/4834/m0138-protocol
Category: ESCs, Sensors and Accessories (https://forum.modalai.com/category/15/escs-sensors-and-accessories)
Tags: esc
Posted: 2025-10-24 13:29:26 UTC by LV.Office Holder
Replies: 1 · Views: 1584

## LV.Office Holder · 2025-10-24 13:29:26 UTC

Hello,

We are interested in ESC 4in1 - M0138. We have a couple of questions regarding how to control it:

https://www.modalai.com/collections/blue-uas-framework-components/products/m0138?variant=47413130101040

Please advise if it is possible to control it via PWM or only via UART
And what UART protocol is used?

Thanks!
 
Victor

## Reply by Alex Kushleyev (ModalAI staff) · 2025-10-24 18:13:58 UTC

Hello @LV-Office-Holder,

The M0138 racing ESC only has two I/O pins and they are used for aux PWM output. PWM input is disabled for this ESC due to lack of PWM input for each ESC channel.

The ESC  protocol example can be found here : https://gitlab.com/voxl-public/support/esc-driver as well as part of PX4 implementation : https://github.com/modalai/px4-firmware/tree/voxl-dev/src/drivers/actuators/voxl_esc . I would suggest referencing the PX4 implementation since it has the latest updates.

Additionally, we have `voxl-esc` test tools (python) : https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-esc . The test tools allow you to spin motors, plot data, perform firmware and parameter updates.

Please let me know if you have any other questions.

Alex