AVR-Chat

What about buffering the SD from 5V to 3.3V. I have done this and it works
fine. Allowed me to run the Mega at 16MHz at 5V and still use the SD at
3.3V.
 
Might be easier than trying to find a faster CPU at 3.3V.
 
Dave...
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Very funny Scotty, now beam down my clothes!!!
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From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of farhan ahmad
Sent: 29 January 2011 18:10
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] ATMEGA64L, ATMEGA64
 
  
Hello All,

I just want to have feedback about some tests made by me. I have been
working with ATMEGA64L. ATMEGA64L-8AU (Vdd=2.7V to 5.5V) works with 8MHz
external crystal oscillator as stated in the specification. 

Since I am using SD card and I am extracting data from SD card and send it
to the TFT display. I am facing the problem of speed, as with 8MHz crystal
oscillator, I found that out the data to be displayed on the TFT screen is
very slow. So, I decided to use ATMEGA64-16AU with 16MHz crystal oscillator
but after looking at the datasheet found out that ATMEGA64-16AU
micro-controller works with the 4.5V to 5.5V Vdd range and for this reason I
cant use the controller because SD card works with 3.3V Vdd. 

Then I use the same micro-controller ATMEGA64L-8AU and use the 16MHz
external oscillator crystal. I found out that the data to be displayed on
the TFT is pretty fast but the problem is that it is beyond the
specification because ATMEGA64L-8AU (Vdd=2.7V to 5.5V) can only work with
8Mhz external crystal oscillator.

Could somebody comment what are the pros and cons of using ATMEGA64L-8AU
with 16MHz oscillator crystal. 

Best Regards,
Farhan Ahmad 


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