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I've a new ESP32-H2 that works fine as a Matter device if it is powered from USB port.

When I try to power it from 3V3-Battery pin using a very reliable power supply (Keithley Model 2231A-Triple-channel DC Power Supply) the board doesn't work fine and Matter doesn't work in any way.

enter image description here

I've read that is needed to use decoupling capacitors, respectively of 22uF and 0.1uF, near (very close) to the 3V3 pin on the board.

Anyway I've some doubts that this will be the real reason of the issue because the power supply seems to me very affordable.

I haven't just tested the decoupling solution but before doing this I'd like to have confirmation that this will be the right solution to the problem that ESP32-H2 doesn't work when powered via external power supply and 3V3 pin.

Any idea?

Thanks in advance

enter image description here

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  • \$\begingroup\$ We don't know which exact ESP32-H2 board you have and what does the schematics look like. How do you know it can be fed with power in to the 3.3V pin or if it damages? Is the battery pin different from regular 3.3V pin? \$\endgroup\$
    – Justme
    Commented May 13 at 18:15
  • \$\begingroup\$ @Justme Hi, thanks for your reply. I've updated my question with detailed pin layout of the board I'm using \$\endgroup\$
    – M4Biz
    Commented May 14 at 8:28

2 Answers 2

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The VBAT pin can't used for powering the board.

It is used for powering the real-time clock and small part of the memory from a backup battery, while in deep sleep mode.

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  • \$\begingroup\$ Hi justme. Sorry for delay in my answer. Even powering the board from 3V3 pin (not 3V3-Battery) the result is the same Matter doesn't work. \$\endgroup\$
    – M4Biz
    Commented May 18 at 14:20
  • \$\begingroup\$ @M4Biz Well can you power it from the 5V input? Can you power anything from the Keithley? Can you light up a LED? Can you use a multimeter to measure voltages? And maybe most important question, which wires and how are you connecting between Keithley and the ESP board, and is the Keithley output turned on, at correct voltage, and some reasonable current limit like 1A? Is Jumper J5 present or disconnected? \$\endgroup\$
    – Justme
    Commented May 18 at 14:57
  • \$\begingroup\$ Hi justme. I've updated my original post with the current configuration \$\endgroup\$
    – M4Biz
    Commented May 18 at 17:43
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Ok. Problem solved. Mistery unraveled. The issue is related to the fact that when we power on the board from external 3.3 V power supply ,if we do nothing, the ESP32 goes in a wait state:

enter image description here

This is due , as specified in the official datasheet to the need of, litterally, :

enter image description here

For this reason using an RC circuit on EN (RST) we have the needed delay between the the primary switch that power on the board and the signal on RST pin, all like this:

enter image description here

In this way the board start succesfully even if powered from an external 3.3V power source.

P.S. for now I've powered the board only from the 3V3 pin and not 3.3V battery pin.

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