TFT displays - why are some recognized as monitors and some are not?

EL Wire/Tape/Panels, LEDs, pixels and strips, LCDs and TFTs, etc products from Adafruit

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ebyerly
 
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TFT displays - why are some recognized as monitors and some are not?

Post by ebyerly »

Here are two tiny screens:
* https://learn.adafruit.com/adafruit-1-3 ... d-displays
* https://learn.adafruit.com/adafruit-min ... i?view=all

Comparing the two guides, I infer the first one _cannot_ be recognized/used as a monitor by a Raspberry Pi out-of-the-box and the second one _can_ be recognized/used as a monitor by a Raspberry Pi out-of-the-box. Why? Can the first one be modified in a way to give it that capability?

It feels like an ~obvious question to someone with the background, so I'm hoping the answer is a link to an already-written guide/reference/whatever, but I don't seem to know the right jargon to Google it myself.

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dastels
 
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Re: TFT displays - why are some recognized as monitors and some are not?

Post by dastels »

The Mini PiTFT won't work "out of the box" as a monitor. You need to install the appropriate kernel driver to get the console to show up on it. Without that it's just a SPI based display that mounts conveniently on the Pi header.

From the tutorial at https://learn.adafruit.com/adafruit-min ... spberry-pi:
There's two ways you can use the 240x135 display.

Be aware that you can only choose to do one way at a time. If you choose the hard way, it will install the kernel driver, which will prevent you from doing it the easy way.

The easy way is to use 'pure Python 3' and Pillow library to draw to the display from within Python. This is great for showing text, stats, images etc that you design yourself. If you want to do that, skip this page and go to the Python install/usage page

The hard way is to install a kernel module to add support for the TFT display that will make the console appear on the display. This is cute because you can have any program print text or draw to the framebuffer (or, say, with pygame) and Linux will take care of displaying it for you. If you don't need the console or direct framebuffer access, please consider using the 'pure Python' technique instead as it is not as delicate.
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ebyerly
 
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Re: TFT displays - why are some recognized as monitors and some are not?

Post by ebyerly »

@dastels, could I rephrase that: the difference between the first display and the second display is Adafruit has a published configuration that tells the Raspberry Pi's OS how to interface with the display as a console? Reading adafruit-pitft.py is probably sufficient for what I'm trying to understand.

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dastels
 
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Re: TFT displays - why are some recognized as monitors and some are not?

Post by dastels »

You have it in essence. A kernel driver is a bit more than configuration, but it basically tells the Pi how to use the display in an integrated way. https://learn.adafruit.com/adafruit-min ... thon-usage shows how to use it from python.

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