Power Pins

  • PWR - this is the power output pin from the USB-C port. It can output 3V or 5V depending on the position of the voltage selector switch.
  • GND - common ground for power and logic.


  • UPDI - This is the logic output from the UPDI Friend. Connect it to the UPDI data pin on the board you are programming. Its logic level is determined by the position of the voltage selector switch (3V or 5V).

Unlike our simple UPDI version, this board is HV for High Voltage because it will let you send a quick 12V pulse to the UPDI right before programming. This is required for when the chip is configured to use the UPDI pin as a reset or GPIO. This board will also let you 'unbrick' any chip configured for HV usage, you can use it to reset the fuses for Low Voltage programming.


The JST SH port is located above the UPDI, PWR and GND pin. It lets you connect to those same pins without any soldering using a 3 pin JST SH cable. A male pin connector cable is included with the UPDI Friend. Optionally, a socket pin connector version is available.

The red wire is connected to PWR, the black wire is connected to GND and the white wire is connected to UPDI.

Voltage Selector Switch

In the middle of the board is the voltage selector switch. You can use this switch to change the power and logic level to 3V or 5V. The 3V regulator can source up to 500mA.


  • Power LED - Below the voltage switch is the power LED, labeled PWR. It is the green LED.
  • Serial activity LED - To the right of the voltage switch is the serial activity LED, labeled TX. It is the red LED. It will light up anytime data is transferred to the UPDI pin.

This guide was first published on Feb 05, 2024. It was last updated on Jun 25, 2024.

This page (Pinouts - High Voltage) was last updated on Jun 25, 2024.

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