Use auxiliary m8 to connect a microcontroller

TECL

I’m looking to get either an OAK-D PRO or its PoE variant. And the choice will depend on the answer to the following question: Can another device be connected to the auxiliary M8 port of the PoE variant, be powered by it, and send data back through the ethernet cable through the camera?

To be more precise, in my case this device will be a microcontroller (ESP32 or Arduino) connected to sensors complementary to the OAK-D PRO (PoE?), and this microcontroller needs to send its sensor data back to the computer running ROS2 at the other end of the ethernet cable.

So my solutions are either to go from my PoE cable to USB (data + power), splitting it with a USB hub to go to the classic OAK-D PRO and my microcontroller, or do what was mentioned above: PoE → camera → auxiliary USB → microcontroller, which I much prefer (if it works).

(By the way, if anyone reading this has a much better idea than the two above, I’m willing to hear it. Just know that power and data MUST come from the ethernet cable.)

Thank you in advance for helping me find an answer to my weird question 😅

jakaskerl

TECL
The M8 port is not meant to supply power to external devices. The only way to do it would be a FFC-4P-POE which allows daisy chaining the devices together.
The USB solution will work fine, though you can not communicate between the ESP/OAK since OAK doesn't expose a GPIO or other interfaces.

Thanks,
Jaka

TECL

jakaskerl

Thanks for your answer Jaka !

I get what you say about the ESP and OAK not being able to communicate with the USB solution, but that shouldn’t be an issue.

Regarding the M8 port, if I understand correctly, the communication wouldn’t be a problem, but power would?

Just to be sure that I get it, let’s say I get power from somewhere (a battery or sipping from the PoE with something similar to a FFC-4P-POE) would using the M8 work?

To be honest, I wasn’t expecting that to be the problem. Especially when the datasheet (which I might misunderstand) says “This pin [talking about the M8’s 5V] is used for sourcing 5V power to accessory devices connected to the M8 connector”. Maybe I should have specified the sensors I plan to use consume next to no power, so the 2W coming from a USB2 should be plenty. Is there something I’m getting wrong with the datasheet?

TECL

jakaskerl

Hi TECL

TECL Regarding the M8 port, if I understand correctly, the communication wouldn’t be a problem, but power would?

Yep. Though communication is limited to a single GPIO pin which you can toggle from the script node or read it there.

TECL To be honest, I wasn’t expecting that to be the problem. Especially when the datasheet (which I might misunderstand) says “This pin [talking about the M8’s 5V] is used for sourcing 5V power to accessory devices connected to the M8 connector”. Maybe I should have specified the sensors I plan to use consume next to no power, so the 2W coming from a USB2 should be plenty. Is there something I’m getting wrong with the datasheet?

I think that is a mistake in documentation. Check the VBUSIN (M8 pin 5) - current is meant to flow in (to VBUS), not out.

Thanks,
Jaka