pitft28-resistive overlay causes the /dev/spi__ devices to d
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pitft28-resistive overlay causes the /dev/spi__ devices to d

by ChiefEngrNY on Mon Jun 14, 2021 3:58 pm

OK... I have the PiTFT Model 2298 (with the 4 buttons up the short end of the panel), a Raspberry Pi 3 Model B (not B-Plus), and a copy of Lady Ada's Adafruit PiTFT - 2.8" Touchscreen Display for Raspberry Pi PDF Document which was last updated on 10-June-2021. I have downloaded the specific "...last known for-sure tested-and-working..." version of the RPi OS (Buster Based dated 04-Dec-2020) and have connected everything up.

Obviously, since I am writing this, things are not working as advertised.

In trouble shooting, I have discovered that the /dev/spidev0.x devices are not present, even though SPI is enabled in /boot/config.txt. What I noticed that has me concerned is that if I comment out the dtoverlay=pitft-resistive,rotate=90,speed=64000000,fps=30 statement in /boot/config.txt and reboot, the /dev/spidev0.x devices re-appear (/dev/spidev0.0 and /dev/spidev0.1). Remove the commenting and they're gone again on the next reboot. Of course, the framebuffer device /dev/fb0 is always present but /dev/fb1 is only present when the dtoverlay statement is active (and the SPI devices are gone).

I used the interactive installer and answered No to both of the "would you like such and such on the display" questions so I can use it as a Raw Framebuffer Device.

Anybody been down this road before and know a way out of the woods?

Please note that I am not a new-comer to electronics, Linux, microprocessors, etc -- been at this for decades. I am just hoping to save some time by finding out if there is already a solution for this problem (that doesn't involve a sledge hammer, chainsaw, or going and finding another display).

Any thoughts, tips, links, pointers that will lead to a solution are greatly appreciated.

Thanks in advance for your help!


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Joined: Mon Jun 14, 2021 3:34 pm

Re: pitft28-resistive overlay causes the /dev/spi__ devices

by adafruit_support_carter on Wed Jun 16, 2021 1:59 pm

Not sure what the problem here is. Is it simply the confusion about the existence of the /dev entries for SPI and how they relate to the device tree overlays?

Or is the display not working? You answered "no" to both output options, so are using the TFT as a raw framebuffer:
https://learn.adafruit.com/adafruit-pit ... 2982165-50
It won't show anything without some additional work.

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Joined: Tue Nov 29, 2016 2:45 pm

Please be positive and constructive with your questions and comments.