USB-BUB logic level

Problems uploading, serial connections, BUBs, P4, FTDI cables, etc
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BobW2
Posts: 2
Joined: Mon Sep 16, 2013 9:39 am

USB-BUB logic level

Post by BobW2 » Mon Sep 16, 2013 9:54 am

Is it OK to set the Logic Level on the USB-BUB-I to 3.3v when uploading to a BBB (optiboot) powered at 5V ?

I have always set the logic level of my USB-BUB at 5v, but accidentally left it at 3.3v prior to uploading today.
The upload went fine.

Would it therefore be OK to permanently connect the Logic Level jumper to 3.3v ?
Then, would I be able to program BBBs or RBBBs running at either 3.3v or 5v, without fussing with the pin header jumper.

Thank you.

BobW2

PS - reason this came up was that I had the jumper set at 5v and connected it to a TP-Link 703n, which runs at 3.3v, and this seems to have killed it. This wouldn't have happened if USB-BUB was hardwired to 3.3v.

paul
Site Admin
Posts: 706
Joined: Mon May 12, 2008 4:19 pm

Re: USB-BUB logic level

Post by paul » Tue Sep 17, 2013 9:41 am

BobW2,

Not only is it fine to set the logic level to 3.3Vs on both BUBs, it is the default setting on the BUB2 that comes with the solder jumpers set to that level.

The reason, as you have found out, is that it is more universal. 5 volt boards still see 3.3volts as logic high.

Paul

BobW2
Posts: 2
Joined: Mon Sep 16, 2013 9:39 am

Re: USB-BUB logic level

Post by BobW2 » Tue Sep 17, 2013 11:34 am

Thank you Paul !

Bob

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