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Freigegebene technische Dokumentation veröffentlicht; Text-only und noindex

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'''Documentation notice:''' This technical documentation was independently rewritten from an archived supplier source. Check technical details and commands against the product version and manufacturer documentation before use.

== Summary ==
The Waveshare 4inch DSI LCD (WSAL21687) is a capacitive touch display with an IPS panel, 480×800 resolution and optical bonding. It connects directly to a Raspberry Pi via the DSI interface and supports Pi5/CM5/4B/3B+/3A+/3B/CM3+/CM3 as well as Bookworm, Bullseye and Buster systems.

== Related products at JW Tech ==
* [https://shop.jw-tech.eu/p/WSAL21687 WSAL21687 – 4inch Capacitive Touch Display for Raspberry Pi, 480×800, DSI Interface, IPS, Optical Bonding Screen]

== Technical overview ==
* Resolution: 480×800 pixels; IPS panel with optical bonding for improved image quality.
* Five-point capacitive touch with toughened glass (hardness up to 6H).
* Connects via DSI1 (recommended) or DSI0 depending on board; Pi5/CM4/CM3+/CM3 have two MIPI DSI interfaces.
* Supported boards: Pi5, CM5, 4B, CM4, 3B+, 3A+, 3B, CM3+, CM3.
* Supported operating systems: Bookworm, Bullseye and Buster.
* For Bookworm/Bullseye: add dtoverlay=vc4-kms-dsi-waveshare-panel,4_0_inch to config.txt; DSI1 is the default.
* For Buster: install the driver from the Waveshare-DSI-LCD repository (e.g. WS_xinchDSI_MAIN.sh 40 I2C0) or use a pre-installed image.
* Display rotation via GUI settings (Screen Configuration → Screen → DSI-1/DSI-2); synchronized rotation of display and touch is fully supported only on Trixie according to the source.
* Backlight brightness can be controlled by software.
* Maximum refresh rate over DSI: 60 Hz.

'''Commands and examples – verify before use:'''
<syntaxhighlight lang="text">
dtoverlay=vc4-kms-v3d
dtoverlay=vc4-kms-dsi-waveshare-panel,4_0_inch
git clone https://github.com/waveshare/Waveshare-DSI-LCD
cd Waveshare-DSI-LCD
sudo bash ./WS_xinchDSI_MAIN.sh 40 I2C0
sudo reboot
dtoverlay=WS_xinchDSI_Screen,SCREEN_type=1,I2C_bus=10
dtoverlay=WS_xinchDSI_Touch,invertedx,swappedxy,I2C_bus=10
</syntaxhighlight>

== Notes and version constraints ==
* The exact kernel version must be checked before installing the driver (uname -a); the source references subdirectory 6.1.21 as an example – other kernel versions require choosing the matching directory.
* System updates under Buster may overwrite previously installed driver files; the driver must then be reinstalled.
* When changing the motherboard (e.g. from Pi4B to Pi3B+), the appropriate drivers must be reinstalled.
* Synchronized rotation of display and touch is fully supported only on Trixie according to the source; on Bookworm/Buster the setting paths differ.
* The DIP switch defaults to I2C-0; using the 40-pin I2C port (I2C-1) requires switching the DIP switch and using a 4-PIN header.
* Beware of knock-offs: the source warns about untested copies without support – authenticity should be verified before purchase.

== Source and revision record ==
* [https://www.waveshare.com/wiki/4inch_DSI_LCD 4inch DSI LCD - Waveshare Wiki]
* Source revision: 105336
* Captured: 2026-09-03T03:15:24+00:00
* SHA-256: <code>1e79e96d8de4aa18d44768b0a3943e36c379f77a56976f9e998feb76c31c93fb</code>

WSAL21687 – 4inch DSI LCD/en - Versionsgeschichte

JWTechPublisher: Freigegebene technische Dokumentation veröffentlicht; Text-only und noindex