Atmega328p Xplained mini --- where are R300 and R301?

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cal-linux
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Posted by cal-linux: Mon. Aug 31, 2015 - 11:58 PM
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Hi,

 

So, I want to connect an Xplained Mini in a little stand-alone box, no USB;  I have a 12V power supply that I want to use as power source.

 

So, that's easy (one would think) --- as I understand from the manual, both J300 and J301 need to have pins 2 and 3 connected, but I also need to remove R300 and R301.

 

Easy, right?   Except that *where on earth* are R300 and R301????!!!

 

Sorry group, I know I'm sounding a bit hostile;  but seriously, Atmel people:  what the hell???   Nowhere in the manual, nowhere *on the board*, *nowhere* does it say.   I mean, unless it turns out that there are two or three different versions of the manual on Atmel's web page --- I can assure you that the one I'm looking at (http://www.atmel.com/Images/Atme...) does not have it.   Incidentally, through a Google search I stumbled into an online/HTML version of the manual;  that one does include an additional figure with the diagram  (a *very wrong* thing already --- two different instances of the manual of the same product, and their contents are different!);  but it still does not indicate *where* on the board are R300 and R301 located.

 

Ok, ranting's over .....  Anyone out there would have this information?

 

Thanks,

Cal-linux

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This topic has a solution.

Tags:

AVR Microcontrollers, megaAVR and tinyAVR, solved
Last Edited: Tue. Sep 1, 2015 - 01:12 AM
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alexru
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Posted by alexru: Tue. Sep 1, 2015 - 12:15 AM
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Full design documents are available here http://www.atmel.com/tools/mega3...

 

The schematic PDF also includes board layout at the end.

NOTE: I no longer actively read this forum. Please ask your question on www.eevblog.com/forum if you want my answer.

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alexru
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This reply has been marked as the solution. 
Posted by alexru: Tue. Sep 1, 2015 - 12:17 AM
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NOTE: I no longer actively read this forum. Please ask your question on www.eevblog.com/forum if you want my answer.

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DocJC
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Posted by DocJC: Tue. Sep 1, 2015 - 12:26 AM
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Sometimes it seems Atmel tries hard, and then shoots themselves in the foot.

 

SEARCHING on the Atmel sight for Xplained popped up the list of various Xplained PCBs, including the Xplained 328P mini.

 

Now, that took a few clicks, and more than it should have, but here is the tricky part:

 

Go under the SOFTWARE TAB,  yes, read that again, twice, the SOFTWARE TAB to find the Hardware documentation.

Grab the software document and unzip it.

 

It appears that there are two revisions of the PCB.

 

I pulled the following image from one of them, and didn't check the other.

 

Both R300 and R301 are ZERO Ohm resistors, i.e. they are most likely small solder bridge jumpers on the PCB.

They could also be two pads with a thin connecting PCB trace that you can cut with an Xacto knife.

 

In any event, find the 3.3 V voltage regulator chip and follow the traces from the pins to find the "resistors".

 

Good luck!

 

JC

 

 

 

 

Darn, cross post with Alex...

 

Last Edited: Tue. Sep 1, 2015 - 12:28 AM
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alexru
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Posted by alexru: Tue. Sep 1, 2015 - 12:35 AM
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And I guess by populating both of them, they saved a price of two jumpers. Probably something like $0.01 in quantity :)

NOTE: I no longer actively read this forum. Please ask your question on www.eevblog.com/forum if you want my answer.

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cal-linux
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Posted by cal-linux: Tue. Sep 1, 2015 - 01:12 AM (Reply to #3)
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Thanks Alexru and JC!

 

@Alexru:  Thanks for posting the drawing --- though I guess with JC's pointer I would have found it  (I actually did, after reading his reply).

 

I *sort of* had suspected that R300 was that one underneath J300  (and funny how hindsight is always 20-20;  *now* (as in, after having read your reply and seen the drawing you posted) I look at the board --- albeit with a magnifying glass --- and I can *very obviously* notice the two traces that go from each of the J300 pins to each of the R300 pins).

 

Again, thank you so much for the info !!!

 

Cheers,

Cal-linux

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paulbsct
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Posted by paulbsct: Thu. Jun 8, 2017 - 08:26 PM
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I loaded the design files (Rev4) and printed the assembly drawing, attached. Oversight on Atmel's part not to include it in the release package. 

Attachment(s): 

PDF icon ATmega328PB_Xplained_assembly.pdf
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