nOOb's first project. Design check please.

If you put your design in some more common format such as pdf I would take a look at it.

Am 04.07.2013 18:49, schrieb Lyle Krug:

Opinions wanted.

Hi,

I am not familiar with the components you use, I just had a quick look...

1.) Check schematic connections of Q1 to Q6. Both, source and drain are

connected to power supplies!

2.) Check values of R1 .. R12. Depending on the speed of your SPI buses,

they may be a bit high.

Good luck,

Walter

Lyle Krug wrote:

In theory it's going to be a HTTP/FTP server with files stored on an

8GB SDHC.

Fresh design. Never prototyped.

Could be more nouse than signal.

Opinions wanted.

 

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Attachments:

ASP-Design.zip

The level shifting circuit is wired incorrectly. The mosfets will short +5v

to +3.3v

Back to the drawning board.

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Viewed / responded via the newsgroup at

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Now I see where I screwed up. It shouldn't take too long to fix it.

The attached pic is what I was working from.

Thanks for catching my FUBAR.

Here's the (fixed) schematicand board.

Hi Lyle,

Personally I wouldn't implement such level converters, because they will be slow (and I don't know what speed you're planning to run the things like SD card with it). You may get a few MHz speed with the current method (I don't know how fast you want it). If you are planning to run faster, then it is possible to get dedicated level converter ICs. Also, possibly bidirectional functionality is not needed in the circuit (I didn't check the circuit in detail). The only problem with the dedicated IC route is that it's likely to need surface mount (you could seek 'SO' packages, which are large and easy to solder). For example, check out ON semi MC74LCX245 which is available in an SO package, and will allow devices that output 5V to interface with 3.3V logic inputs. In the other direction (3.3V outputs interfacing to 5V logic inputs), you likely may not need any device - to know for sure, you'd need to check what logic families are in use, and their '0' and '1' level thresholds - it is likely fine.

EDIT: As a suggestion, why not run the entire thing from 3.3V, and eliminate your level converters completely? Your microcontroller (ATmega) may run from 3.3V (or replace it with one that does).

That will just leave the LCD at 5V if you cannot replace that too. The LCD could work with 3.3V logic levels, even if it is a 5V device (you'd need to check in the datasheet for the logic threshold voltages for the ATmega output, and the LCD input).