Question about SW1 on Duo


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Got my board about a week ago, been playing around with it.  Very slick.  Question about the user switch though.


Looking at the schematic I see one side of the SW1 switch connected to an FPGA input (O_L1N_VREF_1 or pin 104).  And the switch is just switching between 1 and 0.  And of course an FPGA output pin 139 connects to the AVR reset.


On the blank circuit I remove the switch input ahead of the inverter and change it to a pull down (or pull up).  At this point I expect the user switch to not be doing anything. Blink on the AVR is running fine with the pull down.


Now when I move the switch either up or down, the FPGA restarts, even though I expect nothing to happen.  Or I assume this because the USB port goes away then comes back, and the circuit is reloaded.  The AVR restarts also.


I just can't figure out why.  I know there is a second side to the DPDT switch, but per the schematic it doesn't appear to be connected to anything.


I must be missing something though, because the Duo definitely restarts when changing the switch.


:confused:      --David

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I attached the project.  However I think I found the problem.  I thought this was some sort of logic problem but after your comment about 3v3 connecting to ground I hooked up an ohmmeter across the opposite terminals of the slide switch.  Right in the center, if I move the switch slowly, there is a spot where the opposite contacts are connected.  That's probably not good.  Powered on this would appear to short 3v3 to ground long enough to restart the circuit every time the switch is moved.



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