clemaez
Posts: 25
Joined: Thu Apr 14, 2016 1:55 pm

dtoverlay for official display

Thu May 26, 2016 9:38 am

Hi,

I own an Official 7" display and reading the /boot/overlays/README file I can see there is two overlay designed for this display.

Code: Select all

# Official Rapsberry Pi display touchscreen
#dtoverlay=rpi-ft5406

# Raspberry Pi official display backlight driver
#dtoverlay=rpi-backlight
I got a look at .dts files but I don't really understand the meaning of their content.

https://github.com/raspberrypi/linux/bl ... verlay.dts
https://github.com/raspberrypi/linux/bl ... verlay.dts

My question is mostly simple: should I "load" these 2 overlays ? which features are enable with these overlays ?

Similarly I own a BMP085/BMP180 who also have its overlay dtoverlay=bmp085_i2c-sensor, I have the same question for this one: should I enable it ?

Up to now I was l using the official 7" display without these overlays and it works fine (except the multitouch but I guess its mostly a software problem), same for the BMP085/BMP180 who is correctly detected and readable from Python.

But just in case enabling those overlay can improve something I would be happy to know and then enable them ;-)

Kind regards,
Clément

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Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
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Re: dtoverlay for official display

Thu May 26, 2016 10:30 am

If the firmware finds the display on I2C, then it should automatically tell the kernel to load the rpi-ft5406 and rpi-backlight overlays - you don't need to do it manually.

For the BMP085/BMP180, it depends if you want to use the kernel drivers for it, or implement the protocol in userspace (eg your Python code). If the former then you want the overlay. If the latter you don't.
You can't have both userspace and kernel accessing the same I2C peripheral, so you do have to make a choice.
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clemaez
Posts: 25
Joined: Thu Apr 14, 2016 1:55 pm

Re: dtoverlay for official display

Thu May 26, 2016 5:05 pm

Ok, I will check if the overlay for display are loaded with dtoverlays -l
About BMP085/180 chipset I use Python so I don't need the overlay.

Thanks you for your quick answer.

Kind regards,
Clément

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