Powering the ODYSSEY-STM32MP157C from battery

I’d like to use a Pi powering shield to power the ODYESSY-STM32MP157C board. After staring at the schematics for the board I’ve figured the following out:

  • When a 12V supply is connected, Q7 and Q8 stop the 5V_DC and 5V_USB rails from powering each other
  • When no 12V supply is connected and a 5V supply is connected to 5V_USB, Q7 and Q8 allow current to flow and power 5V_DC and 5V_IN. I’m assuming 5V_IN can deal with reverse current to the MP9943GQ

Now, if I powered 5V_IN through the Pi header- I would imagine current would flow to 5V_USB, or 5V_USB would flow to 5V_IN. This isn’t good.

So it looks like there’s two options here:

  • Not use the USB connector for external devices. This kind of sucks
  • Replace R158 and/or R159 with a wire to the battery’s boost converter. The battery probably wouldn’t like this still since if it ran flat it would get power from the wrong place.
  • Remove Q7 and/or Q8 from the board to remove the ability to power via USB. THis seems like the most sane solution

I would like input to know if I’m going in the wrong direction here and the board actually has the ability to use 5V from another source.



The 5V_DC is the main system power rail, both 5V_IN(which from the Pi header) and 5V_USB(which from the USB TYPE C) are connected to this power rail. The Raspberry Pi also did it like this.

The type C connector is build for just power the board or connect to your computer as a device or both.

With Q7 and Q8, they can protect your computer type A port may be damaged by different 5V power rails are tie to togather.

Hope this can help you.

Huh, thanks for the reply. I replied by email but that didn’t seem to work, so my follow-up question was would removing physically Q7/Q8 and powering 5V_IN by the header avoid any charging or 5V rails powering each other?

Not quite, you also have to remove the R136 to avoid the reverse charging to the DC jack.

That makes sense, but wouldn’t it already do reverse charging when powering from 5V_USB?

No, the Q7/Q8 are used to prevent current flowing from 12V DC/DC output to 5V_USB.

Wouldn’t 5V_USB flow to 5V_DC and 5V_IN?

Okay, so here’s a little update: I managed to desolder R136 and Q7. It was way too difficult to do with my cheap tools. With that I could use the LifePo4wered Pi+ to boot! Unfortunately there’s two issues to solve: The first is that by default it’s on an i2c bus that you have to enable using the full device tree. The second is that the board is sucking out a lot of power, more than I can even charge it with.

Okay, I was wrong. The board idling takes around 500mA of power, I was just charging at 100mA due to a bad USB cable. A fully charged battery on my LifePo4wered Pi+ board can power the Odyessy for a little over 2.3 hours. Not bad!