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I want to know about the VBUS pin connection of the USB connector. I have an ESP32-S3-DevKitM-1 board.
https://docs.espressif.com/projects/esp-idf/en/latest/esp32s3/hw-reference/esp32s3/user-guide-devkitm-1.html

Full PCB Schematic:
https://dl.espressif.com/dl/schematics/SCH_ESP32-S3-DEVKITM-1_V1_20210310A.pdf

I want to know about the VBUS pin of the Micro USB connector (highlighted in green in below image).

enter image description here

My related questions regarding Micro USB connector J4:

  1. What is VBUSB (shown in yellow arrow in above pic)? What is the 'B' at the end of VBUSB and where it is connected to ?
  2. Is the VBUS (pin 1) is connected to VCC_5V (black colored arrow in above pic) ? Is the VBUS (pin 1) at 5 volts or is the diode D7 blocking pin 1 to be at 5 volts?
  3. I want to make VBUS (Pin 1) to 5V. How can I do that? ESP32S3 board says that it can act as USB host. So, it means the ESP board in question can supply voltage outwards through Micro-USB-VBUS and can charge other devices connected to it (ESP32) through USB. So, it means VBUS can be configured for 5 volts? My main goal is to charge USB devices connected to the above ESP32 board through the ESP's USB connector.

I would appreciate answer(s) to any/some/all of above questions.

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  • \$\begingroup\$ The diode prevents your board from sending power down the USB cable to a host device that might be switched off, but still allows your board to be powered from the USB cable. \$\endgroup\$
    – Finbarr
    Commented Oct 11, 2023 at 16:03
  • \$\begingroup\$ "My main goal is to charge USB devices connected..." - could you elaborate on this idea? Do the devices are expected to communicate over USB with your ESP32 acting as some USB device? Or do you expect your ESP32 device to act as a host, so the VBUS will act naturally by default? Do you want your "connected devices" to get any "fast charge" from your ESP32 port? \$\endgroup\$ Commented Oct 15, 2023 at 23:53

2 Answers 2

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  1. There's two USB device side connectors. We don't know what the original designed had in mind and why the node is named VBUSB, but if the other connctor has a node named VBUS, why would the second connector not have e.g. VBUSB for the second VBUS. It is also not connected anywhere else except to the connector J1 and anode of diode D7.

  2. The VBUS pin is not directly connected to VCC_5V but through diode D7. It allows the connector to power the board, but it does not allow the board to output power from this connector to other devices. So the VBUS is not at 5V, unless you have some host connected that provides 5V to ESP board.

  3. It makes no sense to want that. This board is a USB device with USB device side receptacles. The device side is intended to only receive power from USB hosts and power supplies. The device side receptacles are not intended to provide power out towards hosts and power supplies. If you did provide 5V out from a device connector, it would short circuit two power supplies and it might damage one or both power supplies, so you might fry e.g. your PC and laptop if you let them power each others through USB ports of ESP. I suggest not to modify the USB connector to provide power, but to solve whatever problem you have in another way.

I think you may have an XY problem, you have problem X which we don't what it is, and you are trying to solve that by making dangerous modifications to allow 5V out of USB connector into wrong direction, and asking how to get 5V out into wrong direction.

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  • \$\begingroup\$ Regarding point 3. ESP32S3 board says that it can act as USB host. So, it means the ESP board in questions can supply voltage outwards through Micro-USB-VBUS and can charge other devices connected to it (ESP32) through USB. So, it means VBUS can be configured for 5 volts? Have I misunderstood something ? My main goal is to charge USB devices connected to the above ESP32 board through the ESP's USB connector \$\endgroup\$ Commented Oct 11, 2023 at 16:15
  • \$\begingroup\$ The fact that the ESP32 can be a USB host does not mean the hardware around it is built to be the host. Clearly it is built as a USB device, if not for any other reasons but not having a host connector to begin with, and not providing 5V out from a host connector. You could use a MicroUSB OTG adapter but as the ESP32 board cannot detect OTG adapters and cannot provide 5V out so having no OTG support does not help. So what you could do is to use an OTG adapter and modify the adapter or ESP32 to provide 5V out. But it has to be 5V so it's not good enough if it's 5V through the diode. \$\endgroup\$
    – Justme
    Commented Oct 11, 2023 at 16:22
  • \$\begingroup\$ Thanks a lot. What do you mean by this at the last - But it has to be 5V so it's not good enough if it's 5V through the diode ? You mean I should bring 5V from somewhere and properly regulate it and then apply that 5V to the OTG connector alongwith D+ D- pins ? \$\endgroup\$ Commented Oct 11, 2023 at 16:48
  • \$\begingroup\$ @AlphaParticle, "You mean I should bring 5V from somewhere" - is not it quite obvious that if you want to source +5V on VBUS pin, you need to bring it "from somewhere"? \$\endgroup\$ Commented Oct 16, 2023 at 0:04
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  1. To the host USB connector. When using a USB cable, this is your positive supply input.
  2. No, it is connected to the anode of D7. If you apply external voltage (not through the USB connector) to your board, you apply it between Vcc_5V and GND. The diode blocks this voltage, to protect the host's USB port.
  3. Connect a USB cable to a host. The host will provide 5Vdc, assuming your board conforms to the USB port power capability.
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  • \$\begingroup\$ Thanks. Actually ESP32S3 board says that it can act as USB host. So, it means the ESP board in questions can supply voltage outwards through Micro-USB-VBUS and can charge other devices connected to it (ESP32) through USB. So, it means VBUS can be configured for 5 volts? Have I misunderstood something ? My main goal is to charge USB devices connected to the above ESP32 board through the ESP's USB connector \$\endgroup\$ Commented Oct 11, 2023 at 16:17
  • \$\begingroup\$ @AlphaParticle, to act as "OTG" port, the board needs to use the ID (pin4) on the USB connector. The board does not have this pin connected to anything, therefore it cannot function as you wish. This particular demo board demonstrates only USB device function. \$\endgroup\$ Commented Oct 16, 2023 at 0:11

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