AVR-Chat

I dont think I would use resistors as the R and C input would delay the signal.
A logic gate IC of some sort would be a better solution with low value pull ups on the outputs.

http://www.ckp-railways.talktalk.net/pcbcad17.htm

David VanHorn <microbrix@gmail.com> wrote:                                  Anybody know what the best way is to interface a 5V output on my
 Mega64 to a 3V input on a Nordic RF IC ? The Nordic datasheet
 specifies a max input voltage of VDD + 0.3V (3.3V)
 
 BTDT.
 
 > Best way I could come up with was a voltage divider on each line, but
 > theres six lines, so thats 12 extra resistors !
 
 Resistors are cheap..
 
 You can also use a Szaiklai pair, to convert the 3V outputs to 5V rails
 
 > I need to run the Mega at 5V because of interfacing to other 5V
 > components, so running it @ 3V is not an option unfortunately.
 
 Realize that a high output on a 3V processor is a high input on a 5V CMOS or
 TTL input.
 Lows on both families are compatible.
 
 > I assume that outputs from the Nordic IC to input pins on the Mega
 > will be no problem for straight connection due to the high input
 > impedance of the Mega and I would not need to use the pullsups on the
 > Mega because the RF IC drives the line both low and high. It looks
 > like anything above 1V on the Mega is seen as a 1.
 
 It's not as hard as you think.
 
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