Seeed SoM STM32MP157C: Pins to be connected at least?

Hi, I’ve done my first PCB using the Seed SoM STM32MP157C. I’ve started with the ODYSSEY STM32MP157C schematic and kicked out all parts I do not need. This was a bit too much I guess, because the SoM does not start now…
Is there an example or a documentation showing which pins to connect at least? Or is there someone who could give me a hint?

Attached the schematic. The SoM is flashed with the application that should blink the blue led. When 5V is supplied to 5V_VIN (A2…A16), the red led (power supply) lights up, but the blue led does not blink.

Any ideas? Thank you!!!

@qunanan We attach great importance to this customer, can you help to answer this customer’s questions?

Hi, Can you make sure the board booted from the eMMC?
You can see the system boot log from uart4.
Please attatch the log information to help us solve your problem.


Thank you for your feedback! I don’t get a signal on USART4_TX, so I think there is something wrong with my schematic.

I just found out that pin A66 and A68 were swapped in my symbol (USB2_N and GND), luckily it was possible to fix this. But this did not fixed the problem. The SoM is still working in the ODYSSEY board, so the swapped pins fortunately did not distroyed the SoM.

I’m still not sure about the pinning of the module. I found the schematic of the ODYSSEY board, but is there more documentation available, preferred a minimal example schematic?

It seems to me that the PMIC is not working. The LDO driven outputs are 0V (Core voltages etc.), while VSYS_3V3 is 4.4V(!!!). I suspect that the switched outputs are continously in on state, and so we see the 5V input minus soime diode drop voltage here. The SoM is still working with the ODYSEEY board.
Do I need to wire some of the PMIC-related pins of the SoM?

Hi, it seems there is something wrong with the power supply, may the route trace or mistake pin connection.
To boot the system, it does not need additional circuitry compared with your design.
Also note that the power-up time of the peripheral circuit must be established later than 3V3_SYS.

Ok, I’ll check the pin connection again.

BTW, is there a more detailed hardware description available? For now, I have only found the OrCAD-Files, schematics and mechanical outline description as PDF…

You can find the original design file(sch & pcb) in the wike page with OrCAD format.
You can view the pcb file with Allegro PCB free viewer(check this link

1 Like

Thank you, the Allegro PCB viewer was very helpful for us!

Dear Gerrit.
We have the same problem with the 3.3V pmic voltage.
Would you be able to explain how you solved the problem on your side?

Thanks a lot.

We found the issue on our own.
Pin 1 on the SOM needs to be placed on pin 2 on the boardconnector. There is NO documentation about.
For everyone else who will design a own board with the SOM: Take care about it!