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Author Topic: Can someone explain this "shorted pad" schematic?  (Read 1226 times)
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I took a look through the schematics for the Uno R3 board. I came across this mysterious "RESET-EN" device.
It looks to me like a solderable jumper -- but it is also shorted out in the schematic, making the jumper totally dead.
What am I missing here? (see attached image)
(Actually, the "upload folder is full" so I can't upload it -- see this link instead)
http://www.watte.net/shortedpad.png
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It is a link that is made.
If you want it broken you cut through the thin part of the track.
If you want to remake it you put a solder blob on the two sides of the pad and then join up and short out again.
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If you want it broken you cut through the thin part of the track

Pre-made for surgery. I see. I guess I would have done it as a jumper, but this is probably cheaper if it's an uncommn-but-supported mod.
Thanks for the reply!
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nr Bundaberg, Australia
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Most clone boards do use a jumper, it's much more convenient and doesn't cost any more because you don't have to load the jumper in manufacturing, the user does if he decides to cut the link and still needs the reset function at times. Just put two holes instead of two solder pads.

I'm always rabbiting on about poor design choices on Arduinos and this is another example.

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Rob Gray aka the GRAYnomad www.robgray.com

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In fact most people refer to these as "solder jumpers" and are sometimes made as open and are bridged closed during wave soldering. More reliable than plugins, as they can't accidentally fall off.
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More reliable than plugins, as they can't accidentally fall off.
All true, but a real PITA if it needs changing often and I've never head of a jumper falling off, usually you need pliers to get the buggers off. And if you provide two holes you can still solder bridge them.

That said I've designed a few boards lately with solder jumpers for things that don't change very often.

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Rob
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I second Graynomad's view. However in my opinion the worsest hardware design decision is still the off grid placement of the connectors. Closely followed by placing the reset button not close to the outside.
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worsest hardware design decision is still the off grid placement of the connectors
It is not a design decision it is a cockup.
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NO _ its an "undocumented feature"
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Well the guy who did it described it to me as a cockup. It was late, it had been a long day and it wasn't checked.
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a long day and it wasn't checked.
I get that, done similar on occasion.

That explains the first prototype, but how on earth does it get through to production? You do a couple of protos, realize the problem and fix it. The only way that can happen is if they went straight to 100 boards and couldn't afford to scrap them.

No matter how you cut it I can only see bad engineering practice. I know it was designed for artists, was it also designed by artists smiley

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Rob
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That explains the first prototype, but how on earth does it get through to production?


I believe the error was made and undetected on the first order for 100 boards or so. Being a shoe string start-up operation they probably could not afford to write it off and redesign, so they shipped their first products out along with shield boards that then had to be built to fit the non-standard spacing error design. After that they were reluctant to change the spacing because it would make all their present and 3rd party shield boards incompatible if they corrected it.

 They do regret it I'm sure, but they probably did not dream that the arduino platform would reach so much popularity and fame and to this day still is something to keep them humble even after all their success.  smiley-wink

 There have been several retro fits for this 'problem' for people that really need to utilize standard .1" pin spacing, either with 'bent pin" shield connectors or utilizing 3rd party arduino compatible boards that add extra shield pin pads with standard spacing that one can use by just soldering in a new connector.

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No matter how you cut it I can only see bad engineering practice. I know it was designed for artists, was it also designed by artists

 Not artists but rather professors and grad students with probably little experience with production of other then prototyping projects. I think they hit on much too great an idea, open software coupled with open hardware, and a simple to use IDE that made micro-controller programming easier and cheaper then any other commercial company had offered at the time, to come down too hard on them for this start-up design snafu. There success points to the validity of their initial concept and that sure counts for something, no?

 
Lefty
« Last Edit: January 09, 2012, 06:17:23 pm by retrolefty » Logged

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I think they hit on much too great an idea,
And don't we all wish we could do similar smiley

______
Rob
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I think they hit on much too great an idea,
And don't we all wish we could do similar smiley

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Rob

 To say the least. When you think about how little they actually had to design and build. Most of the software, the compiler, the IDE, the loader, the wiring library, was already created by other open source project groups, maybe even the bootloader? The basic initial board was very minimal in scope, used the PC RS232 com port interface. Like great chefs, they didn't need to create or assemble many ingredients, just add then in the correct proportions, serve at the correct time and temperature and the customers loved it and spread the good word far and wide. Time will only tell how long the customers will keep returning for meals served at arduino, before a newer chef creates something even better tasting.  smiley-grin
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There's a benefit to the non-standard spacing: It magically prevents inserting the shields the wrong way.
Instant polarity keying :-)
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