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I have made my own version of the Leonardo, and I am having USB issues. Plugging it in to a windows computer - nothing happens! If I hold down reset, I get the "device not recognized error", but if I don't hold down reset, Windows acts like nothing is there.

Schematic: (http://i.imgur.com/V76C6GS.png) enter image description here

Fuses Extended: FB (If I program it as CB, then press read again, it comes out as FB?) High: D8 Low: FF

Using Caterina-Leonardo.hex, uploaded with AVR ISP MKII

The board itself is working, if I compile a blink sketch and flash it directly it works great. It's just that when I plug it into a computer, nothing happens.

Any ideas?

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  • \$\begingroup\$ This is going to be a dumb question, based on my ignorance of the platform, but are you certain that image provides USB connectivity? \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 6 '13 at 0:56
  • \$\begingroup\$ I'm not too familiar with the Leonardo, but I'm under the impression that the bootloader makes the chip act as a virtual COM port, which allows you to upload code like a normal Arduino. \$\endgroup\$ – user2461391 Aug 6 '13 at 0:59
  • \$\begingroup\$ You should always have a pullup to VDD on the reset line. A common value is usually 4.7k or 10k. \$\endgroup\$ – DeathBySnuSnu Aug 6 '13 at 2:04
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UCAP does not look right, it should not be connected to VCC, but to a capacitor to GND.

edit: I was rather tired when answering this yesterday, so I omitted the fact that I built my own Leonardo-style design recently, and correctly connecting UCAP made a big difference in getting USB working.

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  • \$\begingroup\$ Thank you! As a quick fix I ripped off the UCAP pin. Now it shows up as "unknown device", which is progress! \$\endgroup\$ – user2461391 Aug 6 '13 at 2:21
  • \$\begingroup\$ Last update - turns out that UCAP pin with capacitor is absolutely critical to operation. Since disconnecting it wasn't enough, I wired in the 1uF cap to ground and now it works perfectly! \$\endgroup\$ – user2461391 Aug 6 '13 at 13:17

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