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