STM32MP157C-DK2 How to use external power supply?

[MPier.2]

I would like to provide power from PI connector. How to avoid error blocking message at the start of the boot that report:

***********************************************

* ERROR USB TYPE-C connection in unattached mode  *

* Check that USB TYPE-C cable is correctly plugged *

*    Current too low, use a 3A power supply!    *

***********************************************

[PatrickF]

Hi,

We did not recommend using Arduino or GPIO expansion connectors to feed 5V to the DK1/DK2 board. the 5V_VIN power routing is not be guaranteed for 3A.

Furthermore, you will probably need to remove Q1 and Q2 to disconnect Type-C VBUS.

If you still want to do that at your own risk, you could remove the warning by choosing one of this 'hack':

• SW: remove this check from the source code
• HW : fake that a Type-C 3A supply is present by connecting a pull-up on one of the CC line (only one).
  • According to USB Type-C standard, you must use either 10 kΩ ± 5% to 4.75 – 5.5 V (e.g. VBUS) or 4.7 kΩ ± 5% to 3.3 V ± 5% (e.g. VDD). Please not that once this is done, I did not recommend to plug anymore an USB Type-C charger (not sure if any side effect of such hack)

Regards.

[MPier.2]

Thanks for the quickly answer.

We would like to use external power only to make a prototype, then we are ready to design our carrier board with the SOM.

For HW solution its clear.

For SW solution, I found on U-Boot source the file stm32mp1.c with function named "board_check_usb_power(void)". What need I do? Force to "return 0" on line 402?

[PatrickF]

Looking at the code, I propose to replace on line 462

		/* with 125ms interval, led will blink for 17.02 years ....*/
		nb_blink = U32_MAX;

by something like

		/* with 125ms interval, led will blink for 17.02 years ....*/
		nb_blink = 4;

So, the message is still there, but after 4 red led blinks (instead of 2^32 blinks !), the boot will continue.

[allard]

I too want to connect a external power supply. My application is fairly low-power, so it should be OK with the DK2. I tried the HW solution 10K from CC1 to VBUS, but somehow I did not get rid of the message. How do I apply the SW solution to the distrubution package? Do i need to make a .patch file or a .bbappend?

EDIT: HW solution works now, 10K should be connected to 5v_IN, not VBUS.