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Topic: Solution for the 5V vs 3.3V problem (Read 13 times) previous topic - next topic

OsuDan

Hey Rob,

Here is what I'm thinking. This first drawing is a rough schematic for just the crosspoint section of pins. Other pins could be added to these and all the rest of the pins would need to be passed through 74LVC16245's as well.



Red trace is on bottom

Blue is on top

Black is on bottom (5v, 3.3v, gnd)

To answer you question about the pins, Mayhew Labs came up with a pretty nice solution.

http://dl.dropbox.com/u/55783756/Photos/go_between_shield_front%20(1).jpg

http://dl.dropbox.com/u/55783756/Photos/go_between_shield_back%20(1).jpg

As you can see, the headers don't go through the pcb, but are instead surface mounted. This way, we could have separate top and bottom circuits.


Dan

CrossRoads

Here's the schematic & layout, please create a version with the parts you are suggesting.
Top & bottom mount surface mount headers would be one way to keep the physical board the same size, as long as its cut back from the USB header.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
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Graynomad

@OsuDan
At this stage a simple block diagram would be clearer, too many parallel lines for me to follow there.

_____
Rob
Rob Gray aka the GRAYnomad www.robgray.com

Graynomad

This is one way I see it working,



It would need the above for every 8 pins you wanted to handle, but if you stick to the standard shield (not Mega) that's only 3x the above I think.

Bear in mind that some control circuitry would be required as well.

XPS = crosspoint switch
BUF = buffer, probably TXB0108

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

GorillaBuilderz

Also take a look at our http://playground.arduino.cc/GorillaBuilderz/LeoShield which is another pin adaptor.

Dale
www.GorillaBuilderz.com


Hey guys,

I've been looking into something like this for a while as well. One thing that caught my eye was this pin converter shield for the UNO/Leo to go between the old pinout and 1.0

http://mayhewlabs.com/products/go-between-shield

Something like this could be implemented with logic converters between the connection points. This could also leads in some other interesting directions as well:

  • Being able to select/designate individual pins as 5v or 3.3v logic

  • Integrating dynamic pin assignment so the pinout could be adaptable to older shields configurations

  • And if you really wanted to get crazy, you could even wire the whole thing up to be driven by an integrated IC so you just add a library to your sketch and assign the pinout and voltage in software.

  • And since I've already gone way out in left field, to complete the prefect conversion shield, add either an IC to linearly scale the analog inputs or a separate 5v 12 or 16 bit ADC



EDIT: Just read the post about the GTL2000 and it got me thinking there has got to be a chip that could route pins and shift logic levels... Yup.

http://www.intersil.com/en/products/audiovideo/video-switching/unbuffered-crosspoint-switches/CD22M3494.html

Thoughts?
The support team, GorillaBuilderz.
www.GorillaBuilderz.com

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