I just got an Atmel XMEGA-A1 Xplained evaluation board and I'm trying to get started, but the documentation is a bit confusing to me.

Page 6 Section 4 has this warning.

Do not power the board without having the jumper attached next to the USB connector or an ammeter mounted. Otherwise, the device may be damaged by power sourcing through I/O pins. The power measurement header is located next to the USB connector, as shown in Figure 3-1.

Figure 3-1 Overview of the XMEGA-A1 Xplained kit

But I don't know what a jumper is. How do I safely turn this thing on?

To clarify, I see the part on the board labeled "Power Jumper" in the diagram, but I don't know what it means by "attached". It's soldered into the board, how could it not be attached? Alternatively, how would I mount an ammeter?

I spent a bit of cash on this thing and want to be sure I don't fry it before I've had a chance to write a single line of code for it.


2 Answers 2


The jumper they're describing is the power jumper, or J300, which:

is connected between the 3.3V regulated voltage from the regulator and the ATxmega128A1 supply. By replacing the jumper with an ammeter, it is possible to measure the current consumption of the ATxmega128A1

Here's a board diagram:

Overview of the XMEGA-A1 Xplained kit

The two pins marked "Power jumper" are set up to allow a jumper to be placed across them. A jumper is a block of plastic with an internal conductor and two holes, exactly spaced to fit the two pins (there's a standard spacing; I believe it's 0.1"). You can have the jumper installed, in which case the two pins are shorted, or removed, in which case the two pins are independent. Jumpers are used to optionally connect circuit elements or durably configure boards.

So, if the jumper is present, then it provides a path for power from the main board power supply into the ATxmega128A1 chip. You can pull the jumper and connect an ammeter, which would let you determine how much power the chip alone is consuming.

But, if you leave the jumper off when you apply power to the board, the ATxmega128A1 won't get power, but the rest of the board will. Then, power will flow from the rest of the circuit into the ATxmega128A1 I/O pins, killing the ATxmega128A1. And you don't want to kill the ATxmega128A1.

  • \$\begingroup\$ I've added more details to the answer. \$\endgroup\$ Jul 23, 2015 at 11:18

The "jumper" is a small plug that electrically connects the two pins indicated in the diagram in Daniel's answer.

The picture below is borrowed from https://electronics.stackexchange.com/a/74261

Illustration of jumper

So to safely power up the board, ensure that one of these is fitted across the two pins labelled "Power Jumper".

The board is pictured without one in the documentation, but it comes pre-installed on a new board.


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