Question on Schmitt Trigger input with a 3.3V Serial device

[rsocor01]

Hi,

You will need to use a level voltage converter to step up the serial signal from 3.3 to 5.0V. Of course that would be an extra component in your circuit. Can you run the GPS at 5V?

Robert

[khufumen]

Unfortunately, the GPS unit can't use 5 volts. I found a chip from On Semi Conductor, MC74VHC1GT,
which looks like it will do the trick.

Strange thing I noticed:
I have an Atmel AT45 memory chip connected to PortD (D0,D1,D2,D3) and it works fine. This is
weird because PORTD is all schmitt triggers as well in I/O mode and the Atmel memory chip runs at 3.3V. It
shouldn't work but it does [scratching my head]

[Gusse]

Hi khufumen,

Check AN10441 application note, page 4, Fig. 1.

BR,
-Gusse-