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ramkumarkoppu
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June 2, 2021
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My STM32MP157F-DK2 is powered by 5V 3A PSU. but at the boot up time, always it displays the warning

  • June 2, 2021
  • 1 reply
  • 2179 views

My STM32MP157F-DK2 is powered by 5V 3A PSU. but at the boot up time, always it displays the warning 

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

*    WARNING 500mA power supply detected    *

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

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

**

At the end of the boot process, I do see following display as well:

root@stm32mp1:~# [  33.112323] usb33: supplied by vdd_usb

[  33.114843] vref: supplied by vdd

[  33.118045] vref: disabling

[  33.120724] vdda: disabling

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    Best answer by PatrickF

    Hi,

    The warning about power supply is because your Type-C power supply is not compliant to the USB PD standard regarding it's signalling on CC1/CC2 lines. Usually it is because using a Type-A -> Type-C cable.

    You could refer to section 5 of TA0357 for an overview of CC lines we use to detect power adapter characteristics per USB standard.

    See also https://community.st.com/s/question/0D50X0000Bftr1ySQA/power-supply-for-stm32mp157cdk2 for a list of tested supplies ((far to be exhaustive !. Meanwhile we added ASKSTORM models from a well know Swedish furniture retailer).

    If your supply is rated 3A on the output you are using, it is just that SW cannot know it. You could continue like that, it is just a warning.

    On DK2, we use ADC to measure the voltage on cc lines, you can skip this test by commenting the following line in uBoot Device Tree:

    		/* st,adc_usb_pd = <&adc1 18>, <&adc1 19>; */

    For the second question, it is simply some dmesg log which come after login (last two lines are because Linux is disabling unused supplies, here because ADC which was used in uBoot is no more requested as not enabled on kernel Device Tree)

    Regards

    1 reply

    P
    PatrickFAnswer
    Technical Moderator
    June 3, 2021

    Hi,

    The warning about power supply is because your Type-C power supply is not compliant to the USB PD standard regarding it's signalling on CC1/CC2 lines. Usually it is because using a Type-A -> Type-C cable.

    You could refer to section 5 of TA0357 for an overview of CC lines we use to detect power adapter characteristics per USB standard.

    See also https://community.st.com/s/question/0D50X0000Bftr1ySQA/power-supply-for-stm32mp157cdk2 for a list of tested supplies ((far to be exhaustive !. Meanwhile we added ASKSTORM models from a well know Swedish furniture retailer).

    If your supply is rated 3A on the output you are using, it is just that SW cannot know it. You could continue like that, it is just a warning.

    On DK2, we use ADC to measure the voltage on cc lines, you can skip this test by commenting the following line in uBoot Device Tree:

    		/* st,adc_usb_pd = <&adc1 18>, <&adc1 19>; */

    For the second question, it is simply some dmesg log which come after login (last two lines are because Linux is disabling unused supplies, here because ADC which was used in uBoot is no more requested as not enabled on kernel Device Tree)

    Regards

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