Hi @Ivan-Gambit
Good questions.
M0078 Tech Docs Reference: https://docs.modalai.com/usb-epxansion-with-fastboot-v2-datasheet/

Yes, if you have a Voxl or Voxl-Flight in an M500, you will need the M0078 PCB to expose the USB host port from J13. You will not use the provided MCBL-00009 in the M0078 kit. Yes, Voxl or Voxl-Flight J13 port was not designed with Doodle in mind, so you are best to use a splice direct from the power cable. The way to do this is as follows: Use the D+/D- and GND from the M0078 4-pin JST "J3" to the Doodle USB D+/D- and one GND
af2cb12a-9843-46f2-b691-8db5c063c365-image.png use the 5VDC and a GND from the Power Module to the Doodle 5V input and GND. In your case, you can remove the jumper from M0078 "J2" since you are not using any VBUS from the M0078 USB connector. If you remove the jumper on M0078 J2, that allows you to use a simple 4-pin JST to JST cable to the Doodle such as https://docs.modalai.com/cable-datasheets/#mcbl-00015 , or convert it to a breakout cable to connect to the Doodle (Sorry I do not know how to advise further since I am not familiar with the socketed versions) Note: Yes, we have that jumper on M0078 to provide an easy way to access the 5V from the power module, but we did also not design that jumper and the traces with Doodle in mind. It was more for devices needing 1A of USB VBUS, not 2A+ that Doodle requires. You can try it, but you may have limited range at the highest power modes, and most of our cables that you would then use are also 1A limited, so problems like voltage droops/sags may occur with that approach.

The key thing in all of this is to make sure you have a common GND, and the return current for USB will go where it needs and the return current for the 5V will follow it's associated GND return path. Also make sure you do not short VBUS to the 5VDC of your splice if you use that jumper J2. Might be best to just leave it off, but since those pins are "HOT" maybe add a bit of Kapton over them to protect against inadvertent shorts.

If you are hesitant to make splices in the power feed for Voxl, you can see if one of our pre-spliced power cables we offer can give you a jump start, such as: https://docs.modalai.com/cable-datasheets/#mcbl-00211 and then remove the JST to provide what you need on the Doodle side. But, if you need all 4 wires for the I2C port on Voxl, you can start with an MCBL-00001 and then just move contacts from one cable to another.... https://docs.modalai.com/cable-datasheets/#mcbl-00001 There really are a lot of ways to do this (sorry if it's info overload).

I'm happy to review your final solution. If you want some extra support we can email you if you want to share more non-public drawings or such. Just let us know! But, if you are willing to share your setup and pics, it would be faster and you'd be helping others in the same situation 🙂

Thanks!

@tpavlic Thank you, glad it helped!