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I've made my own AVR programmer with an Arduino Nano V3 clone. It has been working fine, but yesterday I was trying to program a faulty board that pulled too much current. Was powering via USB and my OSX laptop told me it had disabled it due to pulling too much power.

After that I couldn't power it anymore, not even from a simple phone charger. I thought I had burnt something, but when testing with a DVM I accidentally shorted pin 1 and 2 of the USB connection:

1 - (red) VDC / plus / +5V

2 - (white) Data -

enter image description here

Then it boots up and is powered as long as I have them connected. Without it wont start with any usb connection, laptop or phone charger. Just to show what I mean:

https://photos.app.goo.gl/rtFj6bp3j4SbuYKr1

Why is this and is there something I can do to save this Nano - it seems to be working fine when usb is shorted like this…

Would hate to have to build up another one while waiting for a new programmer from China :)

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  • Try measuring some voltages. Maybe the solder joint on the USB mini-B connector is broken.
    – Gerben
    Jan 17, 2018 at 16:12

2 Answers 2

Reset to default
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When you plug the board in, the computer enumerates it. The normal device descriptor (IIRC) requests 50mA. If you are (as you most likely are) drawing more than that then the computer is quite within its rights to turn it off.

By shorting those pins you are preventing it from enumerating, so the computer doesn't know the requested amount, so it assumes (probably) 500mA.

You can achieve the same effect by using a cable with no data wires in it.

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  • But it's the same with a phone charger thats rated for 1A and worked before. Something has happened with the Arduino.
    – Viktor Hedefalk
    Jan 17, 2018 at 15:27
  • Then maybe it's broken. It looks like a cheap chinese clone, so throw it away and get a new one.
    – Majenko
    Jan 17, 2018 at 15:42
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It's possible you've blown the voltage regulator. If you happen to have a source of those, like another dead Nano, you can try replacing it to see if that works.

Shorting the +5 to data is likely going to destroy your computers USB controller, so please quit.

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