Powering the ODYSSEY-STM32MP157C from battery

Products & Technology ODYSSEY Serials
#1

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.

Odyssey X86 UPS...?
#2

Hi,

Humm~

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.

#3

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?

#4

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

#5

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

#6

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

#7

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

#8

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.

#9

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!