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Thread: ILI9341 on Teensy 3.2 using I2C (SDA & SCK) only?

  1. #1
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    ILI9341 on Teensy 3.2 using I2C (SDA & SCK) only?

    Good morning.

    I have the Teensy 3.2 driving the ILI9341 fully satisfactorily (display only, no touch functions required at present). But I wondered whether there is any way in which I can reduce the pin-count by using the SCK and SDA (well actually the SDI on the ILI9341) pins only, in a two-wire mode?

    Any advice would be gratefully received, but if I am considering the impossible, I'd like to know!

    Kenneth Spencer

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    Quote Originally Posted by kaspencer View Post
    Good morning.

    I have the Teensy 3.2 driving the ILI9341 fully satisfactorily (display only, no touch functions required at present). But I wondered whether there is any way in which I can reduce the pin-count by using the SCK and SDA (well actually the SDI on the ILI9341) pins only, in a two-wire mode?

    Any advice would be gratefully received, but if I am considering the impossible, I'd like to know!

    Kenneth Spencer
    You'd use the SPI hardware to talk to a TFT chip - you need to drive the serial clock, data, D/C and CS pins, and sometimes
    the RESET pin too. I2C hardware is no use, the COG chip requires all those pins to function, and many more in parallel mode.

    If you can configure serial to send 9 data bits the 3-wire mode can be used where the D/C state is transmitted at the 9th
    serial bit, but you still need CS/SDI/SCLK and possibly RESET.

  3. #3
    Senior Member+ KurtE's Avatar
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    I don't know of any direct way to do this. You could use another processor in between the T3.2 and display, where that processor talks to the display and uses whatever format you define to talk to the T3.2, which could be I2C or Serial or ... But it could work.

    Not sure how easy it would be to use some form of I2C Shift register may be able to be made to work.

  4. #4
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    Quote Originally Posted by MarkT View Post
    You'd use the SPI hardware to talk to a TFT chip - you need to drive the serial clock, data, D/C and CS pins, and sometimes
    the RESET pin too. I2C hardware is no use, the COG chip requires all those pins to function, and many more in parallel mode.

    If you can configure serial to send 9 data bits the 3-wire mode can be used where the D/C state is transmitted at the 9th
    serial bit, but you still need CS/SDI/SCLK and possibly RESET.
    Thanks for the reply, Mark. But you've described excatly what I am already doing! I really need to free up just a few more pins, hence my question. But OK - looks as though I will need a Teensy 3.5/6 or better still a 4.1.

    Thanks Kurt! I think I'm going to have to stick with my current design, which is in fact as Mark suggests, and get more pins!

    Best wishes,

    Kenneth Spencer

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