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Driving a 5V I2C touchsceen. — Parallax Forums

Driving a 5V I2C touchsceen.

darkxceeddarkxceed Posts: 34
edited 2009-01-11 17:18 in Propeller 1
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,
Bart

Comments

  • Bob Lawrence (VE1RLL)Bob Lawrence (VE1RLL) Posts: 1,720
    edited 2009-01-11 13:47
    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

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Aka: CosmicBob
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2009-01-11 14:34
    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.
    3V_5V_mosfet.jpg
  • darkxceeddarkxceed Posts: 34
    edited 2009-01-11 17:18
    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.



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