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USBtinyISP working at 3.3 V ?
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USBtinyISP working at 3.3 V ?

by planteg on Sat Oct 22, 2011 8:52 pm

Hi all,

I need some programmer in order to program an Arduino compatible board I will design. This board would work on 3.3 V, so I was wondering if USBtinyISP can drive a 3.3 V powered board without harm ? Having a look at the schematic is a little bit confusing because it shows only one VCC power bus, which means whatever you do, both the buffer and the micro-controller power pins are connected together. But looking at the PCB, one sees that the buffer is either powered from the internal VCC (USB) if JP3 is present or form the external board power line if JP3 is absent. Shouldn't you call these two lines differently ? And I guess that if you put on JP3, the external board should not be powered externally but by the ISP cable.

Thanks a lot.

Gilles Plante
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Joined: Sat Oct 22, 2011 8:24 pm

Re: USBtinyISP working at 3.3 V ?

by adafruit_support_bill on Sun Oct 23, 2011 6:13 am

From the user manual:

Version 2.0 which is almost certainly what you've got, uses a level shifter so that if the jumper is not in place, it will use whatever the target voltage is, a lot better for your low-voltage devices!

So, if you have a device that needs to run at 3.3V or so, don't have the jumper in place!

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Please be positive and constructive with your questions and comments.