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Thread: ILI9341 Signals for SPI

  1. #1

    ILI9341 Signals for SPI

    I have a breadboard and PC board using the T3.2 and ILI9341 touch display, both using the same exact code. The breadboard works fine but the PCB does not (i.e screen is blank and no white screen on initial power up). I have check all ILI9341 signals including 5V, GND, LED, Reset, TFT_DC, TFT_CS, MOSI, MISO and SCLK using a 100 MHz scope. Comparing the ILI9341 TFT_CS, TFT_DC, MOSI and SCLK signals in that order between the breadboard and PCB shows no difference (see inserted waveforms). The 1st set of waveforms is from the breadboard and 2nd set is from the PCB at 100usec timebase. The 3rd set of waveforms is from the breadboard and 4th set is from the PCB at 5 usec timebase. Can you see any signal that look abnormal? I have tried swapping displays and even T3.2's with no change in results. Note: the scope bandwidth resolution is probably limited by the 100 MHz-250 MS/sec and scope probes with respect to SCLK signal rise/fall edges.

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  2. #2
    I have of course ohm'd out all connections between T3.2 and ILI9341 on PCB compared to the breadboard which has always worked and is from Paul's audio workshop. Just don't know what could be different if connections are correct and code is the same. I will try using the ILI9341 test code from Teensy examples menu. I have attached the schematic of the 1st page which shows the connections to the display. Note the schematic shows a T3.5 which I tried with the same results as the T3.2, but either should work with the designated pins for the ILI9341.

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  3. #3
    Just tried the ILI9341 test graphics sketch with the same results (i.e. no display or touch response), so it is not the programming that's the problem. It must be the schematic interconnect. Does anyone see a problem with that?

  4. #4
    Senior Member
    Join Date
    Nov 2017
    I don't see any pullup resistors for TFT_CS & T_CS.

  5. #5
    Senior Member+ KurtE's Avatar
    Join Date
    Jan 2014
    LED Backlight, Looks like you have it connected to GND through resistor? I believe it should to to 3.3 or 5v through resistor...

  6. #6
    Thank you Kurt! That was the problem. Didn't know that the LED pin was more than just for backlighting as I wasn't needed it and thought the 5V was what drove the display. You saved the day! Wish there was a data sheet on the ILI9341, but can't find it on Adafruit website. Is it anywhere else?

  7. #7
    Never mind, I found ILI9341 it.

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