Raspberry Pi Touch Display - eclubiitk/EClub-Handbook GitHub Wiki
Introduction
The Raspberry Pi Touch Display is an LCD display which connects to the Raspberry Pi through the DSI connector. In some situations, it allows for the use of both the HDMI and LCD displays at the same time (this requires software support).
Board support
The DSI display is designed to work with all models of Raspberry Pi, however early models that do not have mounting holes (the Raspberry Pi 1 model A and B) will require additional mounting hardware to fit the HAT-dimensioned stand-offs on the display PCB.
Physical Installation
The following image shows how to attach the Raspberry Pi to the back of the Touch Display (if required), and how to connect both the data (ribbon cable) and power (red/black wires) from the Raspberry Pi to the display. If you are not attaching the Raspberry Pi to the back of the display, take extra care when attaching the ribbon cable to ensure it is the correct way round. The black and red power wires should be attached to the GND and 5v pins respectively.
Screen orientation
LCD displays have an optimum viewing angle, and depending on how the screen is mounted it may be necessary to change the orientation of the display to give the best results. By default, the Raspberry Pi Touch Display and Raspberry Pi are set up to work best when viewed from slightly above, for example on a desktop. If viewing from below, you can physically rotate the display, and then tell the system software to compensate by running the screen upside down.
FKMS Mode
FKMS mode is used by default on the Raspberry Pi 4B. FKMS uses the DRM/MESA libraries to provide graphics and 3D acceleration.
To set screen orientation when running the graphical desktop, select the Screen Configuration option from the Preferences menu. Right click on the DSI display rectangle in the layout editor, select Orientation then the required option.
To set screen orientation when in console mode, you will need to edit the kernel command line to pass the required orientation to the system.
sudo nano /boot/cmdline.txt
To rotate by 90 degrees clockwise, add the following to the cmdline, making sure everything is on the same line, do not add any carriage returns. Possible rotation values are 0, 90, 180 and 270.
video=DSI-1:800x480@60,rotate=90
NOTE: In console mode it is not possible to rotate the DSI display separately to the HDMI display, so if you have both attached they must both be set to the same value.
Legacy Graphics Mode
Legacy graphics mode is used by default on all Raspberry Pi models prior to the Raspberry Pi 4B, and can also be used on the Raspberry Pi 4B if required, by disabling FKMS mode by commenting out the FKMS line in config.txt. Note: legacy mode on the Raspberry Pi 4B has no 3D acceleration so it should only be used if you have a specific reason for needing it.
To flip the display, add the following line to the file /boot/config.txt:
lcd_rotate=2
This will vertically flip the LCD and the touch screen, compensating for the physical orientation of the display.
You can also rotate the display by adding the following to the config.txt file.
display_lcd_rotate=x, where x can be one of the folllowing:
| display_lcd_rotate | result |
|---|---|
| 0 | no rotation |
| 1 | rotate 90 degrees clockwise |
| 2 | rotate 180 degrees clockwise |
| 3 | rotate 270 degrees clockwise |
| 0x10000 | horizontal flip |
| 0x20000 | vertical flip |
Note that the 90 and 270 degree rotation options require additional memory on the GPU, so these will not work with the 16MB GPU split.
Touchscreen orientation
Additionally, you have the option to change the rotation of the touchscreen independently of the display itself by adding a dtoverlay instruction in config.txt, for example:
dtoverlay=rpi-ft5406,touchscreen-swapped-x-y=1,touchscreen-inverted-x=1
The options for the touchscreen are:
| DT parameter | Action |
|---|---|
| touchscreen-size-x | Sets X resolution (default 800) |
| touchscreen-size-y | Sets Y resolution (default 600) |
| touchscreen-inverted-x | Invert X coordinates |
| touchscreen-inverted-y | Invert Y coordinates |
| touchscreen-swapped-x-y | Swap X and Y cordinates |