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Thread: Color 320x240 TFT Touchscreen

  1. #1
    Junior Member
    Join Date
    May 2020

    Color 320x240 TFT Touchscreen

    Are this display and the purple test board compatible with the Teensy 4.0 and 4.1?

  2. #2
    Member MorganS's Avatar
    Join Date
    Apr 2015
    Northern Nevada
    Which purple test board?

  3. #3
    Senior Member+ MichaelMeissner's Avatar
    Join Date
    Nov 2012
    Ayer Massachussetts
    Quote Originally Posted by MorganS View Post
    Which purple test board?
    This board mentioned in the product listing that you can order from Oshpark:

    While in theory, it should run (the SPI pins SCK, MOSI, and MISO are in the same positions), it may not run as fast as it could using the ILI9341_t3 library on the Teensy 4.0/4.1.

    On the Teensy 3.x, there were multiple pins that would allow speeding up SPI actions using DMA in the ILI9341_t3 library. In the purple board, pin 10 is the CS pin, pin 9 is the D/C pin.

    However, on the Teensy 4.0, there is only one special pin (10) that can be sped up with hardware DMA, and it needs to be on the D/C pin. AFAIK, in the t4 code in the library, it is more important to optimize the D/C pin than the CS pin.

    Unfortunately, the purple board uses pin 10 for CS and 9 for D/C.

    The Teensy 4.1 has two additional fast CS pins (36 and 37). I don't know if the library now supports them. Perhaps ILI9341_t3n supports it instead. One of the display experts would need to chime in.

    I just noticed that the pin for the touch input (8) is also used for the I2S microphone. Which means you might not be able to combine sound (i.e. the Audio Shield) and the display using the purple board. The Audio Shield also uses pin 10 for the SD card on the audio shield.

  4. #4
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012
    Yes, confirmed, both Teensy 4.0 and 4.1 work well with this display and the purple test board.

    I tested both just now, and updated the display's page with Teensy 4 info. Here's a photo, so you can see it working with Teensy 4.1.

    I tested with File > Examples > XPT2046_Touchscreen > ILI9341Test, which uses the ILI9341_t3 library. As you can see, it works on Teensy 4.

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