AVR dragon unable to enter programming mode

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Joined Jan 16, 2015
Hello, this is my first time designing a pcb and also my first time using the AVR dragon. I'm trying to program an ATUC256L3U microcontroller (with LED blinky) using aWire. I've been powering the pcb with a pc power supply at ~3.4V. The ground is connected to both the dragon and the PSU (maybe causing problems?). On the standard aWire header I have pin 1 being the MCU n_reset (no 47k pull-up currently), pin 2 being 3.3V for the board and pin 6 being ground for the PSU with the dragon ground being connected elsewhere on the ground plane. I get this error every time and I have no idea what it means. Also, as a side question, why is the target voltage as reported by Atmel Studio 7 is almost always about 0.9V higher then the voltage from the PSU when measured with a multi-meter?

Thanks for reading,
Last edited:


Joined Sep 13, 2015
I'm trying to program an ATUC256LU3
first, make sure that dragon supports your chip.
2nd, make sure that you follow the device datasheet in terms of layout.
3rd, make sure that the layout is correct.
4th, dragon is a little bit fragile. so I would program a known good chip to test.