Re: [avr-chat] AVR board with USB and LCD

[Joerg Wunsch]

Pertti Kellomäki <address@hidden> wrote:

> Yes, I think I can see the pain. Given that the Butterfly specs give
> the supply voltage as 3.1V - 4.5V, and the USB module is rated
> 4.4V-5V, I guess my best option would be to forget the Butterfly's
> battery and drive the whole thing from three 1.5V batteries.

I guess the butterfly is low power enough so a single LED between the
5 V USB module and the 3 V butterfly suffices completely.  Level
shifting is often not necessary, some simple resistors will do it as
well.  3.3 V outputs driving close to rail-to-rail (as it is typical
for CMOS) are well enough within the common TTL-compatible input
window, and for the other direction, the series resistors limit the
current that flows down into the 3 V's input voltage limiting diodes.

-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)