--- In [email protected], "maurizio bertero" <[EMAIL PROTECTED]> wrote: > > hi, > I've got one question relative to the article "Using the I2C driver to > access a HD44780 LCD" (http://www.acmesystems.it/?id=162). > The schematic seems don't care about different logic levels between the fox > board (3.3V) and Philips PCF8574 (5.0V). > I know that Fox's inputs are 5V tollerant so no damage will happen, but I > have some doubt regarding the ability of the PCF8574 to regognize output > levels coming from the FOX (i.e. the I2C clock signal). The PCF8574 > datasheet says that minimun level for the High signal must be 0.7*Vdd (so > 0.7*5=3.5V) but the FOX board can generate that level. Ho can it work ? > > Thanks to everyone for the answers > > Maurizio > > > [Non-text portions of this message have been removed] >
I had a very similar question a while ago (see http://tech.groups.yahoo.com/group/foxboard/message/2855). The PCF8574 works between somewhere 2.5V and 6V, so you can just power it with 3.3V too (thanks to Wouter for highlighting this). Best rgds, --Geert
