View Full Version : Driving a 5V I2C touchsceen.

01-11-2009, 05:54 PM
Hello all,

I have a edip touch screen I used on a siemens C162 proc.(or something like that)·in the past.
Now I want to use it with my prop, using I2C to controll it.

The screen IO is 5V and my prop is 3.3V, will it work when connecting a IO pin from the prop to the SDA of the screen with a 5V/4k7 pull up or do I need something like a max232.

The SDA line has to be bidirectional also.

kind regards,

Bob Lawrence (VE1RLL)
01-11-2009, 08:47 PM
Have a look at the project on Ray's web site. He provides some tips on I2C and 5V. He did some work on tough screens as well but I don't have a link for that. You can try a forum search.

From the web site "Also, by using an I2C "Level Shifter" you can use the I/O pins with other voltages, e.g., 5V. "

www.rayslogic.com/propeller/Programming/i2c/i2c.htm (http://www.rayslogic.com/propeller/Programming/i2c/i2c.htm)

Aka: CosmicBob

PJ Allen
01-11-2009, 09:34 PM
The circuit depicted below is the cat's pyjamas for 3V-5V bidirectional I/O and I've tested it with BS170, VN10L, 2N7000.· The resistors are 5K-10KΩ.

01-12-2009, 12:18 AM
Tanx for the feedback.

I found the ADuM1251 also nice but they cost something like 7euros.

The mosfet solution sounds nice, I will order some of them and test it.