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I am using one of those Chinese clones of the Adafruit TFT LCD and I couldn't find much information about the reset pins on these chips. The way I have it set up is that a MOSFET on the high side switches it on and off through a digital pin as it is required in my specific application. I was able to do that and also as a word of caution to those trying to figure it out, writing all the pins LOW is a must in order to avoid powering it through its protection diodes.

It is working exactly the way I want it to but my concern is that there is not much information about the reset pins on this chip. When powered on, the reset pin is connected to 3.3V but when powered off, what state should I leave the pin in? Currently I leave it floating and since it is not receiving power in any way, the LCD is not fussy about this although I am concerned about it. Is it okay the way it is and about pullup resistors, should I care to put one on this pin?

Some info about my setup, I am using s Teensy 3.2 and the LCD is a 2.4 inch TFT LCD with the ILI9341 driver chip. A digital pin controls the MOSFET which is a logic level NDP6020P switching 3.3V.

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    \$\begingroup\$ Please link to the device data sheet (not the selling site but the actual pdf data sheet). \$\endgroup\$
    – Andy aka
    Commented Nov 19, 2020 at 14:05
  • \$\begingroup\$ You can get more information if yo search for a Linux device driver, under stagging-> fbtft. You control the pins with GPIOs, including reset if you want to have the possibility to initialize the device on the fly. \$\endgroup\$
    – Marko Buršič
    Commented Nov 19, 2020 at 14:12
  • \$\begingroup\$ From what I understand, you're concerned about what state the reset of the screen is when it has no power. If that's the case, It does not matter. Regardless of what you do, the screen has no power and will not be able to do anything anyways. \$\endgroup\$
    – bunker89320
    Commented Nov 20, 2020 at 17:22
  • \$\begingroup\$ @bunker89320 does having the ground pin connected and leaving 3.3V disconnected matter in this case? \$\endgroup\$
    – Slug FPV
    Commented Nov 21, 2020 at 13:54
  • \$\begingroup\$ @SlugFPV if you’re talking about when you turn it off. No it doesn’t matter. \$\endgroup\$
    – bunker89320
    Commented Nov 21, 2020 at 15:05

1 Answer 1

Reset to default
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Okay so I have completed this project and as mentioned above, the reset pin does not end up sourcing current to the chip and does not run it in the 'Zombie' state. I noticed one major issue nevertheless. It is that when the TFT lcd is being powered on, the reset pin must be set to HIGH otherwise the lcd will not power up and initialize properly. The main point being, it doesn't matter what the pin is when the lcd in not powered but when it is being powered on, the pin must be set to HIGH.

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