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J-Link Supply Adapter

The J-Link Supply Adapter provides a fixed I/O voltage level for VTRef. It eliminates the need to connect VTRef (pin1) to the target.



General information

In general, the target provides its I/O voltage level (VTRef) on pin 1 to the debug probe insuring the debug probe uses the right I/O voltages and avoiding damage of the target debug pins. If signal VTRef is not desired on the target board it can be omitted by using the J-Link Supply Adapter, manually setting the I/O voltage. Default I/O voltage is 3.3 V. For increased flexibility the J-Link Supply Adapter can adapt to other target voltages in the range from 1.2 V to 5.0 V by replacing a single resistor on the adapter.

The Supply Adapter can be inserted between J-Link and the target maintaining a 1:1 connection of all debug signals (except VTRef/pin 1). It has a standard 20-pin 0.1" socket towards the J-Link debug probe and a standard 20-pin 0.1" header on the target side. The main reason for using the adapter is to reduce the number of connections to the target, especially in production environments. It can also be used with Flasher ARM. For dual wire debug interfaces such as SWD, typically only 3 wires are still required: SWDIO and SWDCLK as well as GND. For single wire interfaces such as SPD, the number of connections is reduced to 2 accordingly.

The J-Link Supply Adapter is compatible with J-Link BASE, J-Link PROJ-Link ULTRA+, J-Link PLUS and Flasher ARM.


Preparing J-Link to Supply Power

J-Link needs to supply 5V power to the emulator side of the adapter on pin 19. In order to do this, you may have to configure J-Link once as follows:

  • Make sure that SEGGER J-Link software is installed on your machine. It can be downloaded from here
  • Start J-Link Commander, which can be found under “Start -> Programs -> SEGGER -> J-Link”
  • Enter the following command: power on perm
  • Plug in the adapter: The LED on the emulator side should now be lit.