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Thread: buydisplay 1280 X 400 TFT ra8876 AND SSD2828 SPI connectivity

  1. #26
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    Okay, glad you saw that first hand ...I could not identify where the message was coming from ..Still no change , can't write anything to display on the screen ....Hopefully someone will chime in.

  2. #27
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    I have a scope I'll check the SPI out .... I've just not been able to get to it yet .. I'll post an update...

  3. #28
    Senior Member blackketter's Avatar
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    I'm able to trigger the "2D ready failed" with a low voltage on the 5v rail. Could that be an issue for you?

  4. #29
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    Thanks for your reply .. Im building up a new supply for my project and will make sure I have sufficient current ...but I did drive it off a supply that could provide 1.5amps .....but I did check the power regulation and the dropout was too high .. I was down to 4.5v and I suspect it failed to operate ..bad regulator .....im building up a more robust supply this weekend .. so will let you know sometime tomorrow ..

  5. #30
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    No happyness, Built the new supply .. voltage and current are good under load ... Ran an RA8875 off the supply with a teensy 4.1 to test .. all good .... no issues ..

    reconnected the ra8876 display .. confirmed wiring ... Current and voltage load are fine ) Compiled and loaded your test example ... No activity other then the backlight coming on ... This is tough, can't figure out for the life of me what I missed.

    Will pull my scope out of storage ... and check the spi and see what's going on .. If the program is running it should be spewing data on the SPI line

  6. #31
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    Well tried both displays .. Not pulling my hair out yet .. but no luck yet .. This should be running ...but I'm missing something and just have not figured it out yet... LOL

    will keep trying .. power is good , connections are good .. code compiles fine .. uploads fine, backlight is enabled when booted ..but won't write to the screen...

  7. #32
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    blackketter .... I'm at the point I had best take your wiring trace ... I was hoping I would not have to ask you this but , Something is not right ..

    Thanks
    K

  8. #33
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    Okay update .. I switched from the t4.1 to the t4.0 .. I re-did the configuration jumpers a second time ... I have torn graphics on the screen ..colored lines and they appear to be changing periodically so I suspect its the teensy executing the graphics routines ... closer but not quite there yet .. I pushed the ssd2828 connections to pins 23/22/21/20 on the teensy 4.0 ..

    So I am closer now ...

    note I tried it on the t4.1 and no output at all .. so not sure what's going on there..

  9. #34
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    IS there no command to define the screen pixel size? or is it strictly calculated ..?

  10. #35
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    I'm running on the t4.0 , the code appears to be running , display is trying to work , lines across the display , I'm currently using this pinout configuration with the T4.0
    // Pin connection mapping
    ER_TFT0784_t3 tft = ER_TFT0784_t3(
    // Teensy pin // Display pin
    10, // RA8876 CS 5
    14, // RA8876 RESET 11
    11, // RA8876 MOSI 7
    13, // RA8876 SCLK 8
    12, // RA8876 MISO 6
    23, // SSD2828 CS 31
    22, // SSD2828 RESET 43
    21, // SSD2828 SDI 34
    20 // SSD2828 SCK 35
    );

    I am running your example .. But need to sort out why the screen is torn ..open to suggestions
    I played with the SPI clock and no difference..

    but getting closer ..

  11. #36
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    Blackketter.. are you configured for 3 wire spi or 4 wire spi .. I'm configured for 4 wire spi
    Last edited by Keith_M; 04-11-2021 at 08:49 PM. Reason: typo

  12. #37
    Senior Member blackketter's Avatar
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    Same, 4 wire SPI.

  13. #38
    Senior Member blackketter's Avatar
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    Can you post a picture of the tearing on the display? Could be a configuration issue...

  14. #39
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    WOW ... I am at a loss ...LOL .. thanks for the reply ..

  15. #40
    Senior Member+ mjs513's Avatar
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    Quote Originally Posted by blackketter View Post
    Can you post a picture of the tearing on the display? Could be a configuration issue...
    Was thinking that maybe need to lower the SPI Clock setting

  16. #41
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    I had tried spi clock from 40 MHz fown to 20 MHz then finally down to 6 MHz .. and the screen is the same ..I pulled it apart tonight , but the screen is very dim.. I'll put it back together and get a screen shot .

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