The cleanest way to do this is to use a simple level adaptor for the 2 i2C lines, for instance using cheap digital mosfets.
Doing so, the fox board will only see a 3.3 V logic, whereas the rest of the worl will use a 5V logic. Frederic. Geert Vancompernolle a écrit : > > --- In [EMAIL PROTECTED] s.com <mailto:foxboard%40yahoogroups.com>, > "maurizio bertero" > <maurizio.bertero@ ...> wrote: > > > > hi, > > I've got one question relative to the article "Using the I2C driver to > > access a HD44780 LCD" (http://www.acmesyst ems.it/?id= 162 > <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 > <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 > >
