Quelltext der Seite WSAL21434 – CM4-DISP-BASE-2.8A/en

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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 CM4-DISP-BASE-2.8A is a baseboard with an optically bonded 2.8-inch IPS display and integrated capacitive touch. It mounts directly onto the Raspberry Pi Compute Module 4 and is powered via a USB-C connector (5 V / 2.5 A). The unit provides DSI/CSI, HDMI, USB 2.0, I2C, I2S, SPI, Ethernet and FAN interfaces plus an optional M.2 M-key module for PCIe devices.

== Related products at JW Tech ==
* [https://shop.jw-tech.eu/p/WSAL21434 WSAL21434 – 2.8″ Touch Screen Expansion For Raspberry Pi Compute Module 4, Optical Bonding Display, Optional Interface Expander]
* [https://shop.jw-tech.eu/p/WSAL21435 WSAL21435 – 2.8″ Touch Screen Expansion For Raspberry Pi Compute Module 4, Optical Bonding Display, Optional Interface Expander]

== Technical overview ==
* The display is driven through the DPI port rather than HDMI.
* A power supply of at least 5 V / 4 A is recommended; the built-in USB-C input only supplies 5 V / 2.5 A.
* The BOOT switch selects between USB-C boot (ON) and eMMC/TF-card boot (OFF).
* The M.2 module supports PCIe-channel devices only (e.g., NVMe drives); it does not support SATA drives.
* Some devices may require recompiling the kernel if they are not recognized by the official Raspberry Pi image environment.
* On Bookworm, display and touch rotation can be set synchronously via the “Screen Configuration” app; on older systems, touch rotation must be configured separately.
* The USB 2.0 port is disabled by default; to enable it, add dtoverlay=dwc2,dr_mode=host to config.txt.
* To activate the camera, a DTB from a Waveshare file is compiled into /boot/dt-blob.bin; on Buster this is enabled via raspi-config, on Bullseye via libcamera helpers.
* The unit includes an RJ45 Gigabit Ethernet port, three USB 2.0 ports and extended interface access.

'''Commands and examples – verify before use:''' 
<syntaxhighlight lang="text">
dtoverlay=dwc2,dr_mode=host
dtoverlay=vc4-kms-v3d
dtoverlay=waveshare-28dpi-3b-4b
dtoverlay=waveshare-28dpi-3b
dtoverlay=waveshare-28dpi-4b
dtoverlay=waveshare-touch-28dpi
dtoverlay=vc4-kms-dpi-2inch8
video=DPI-1:480x640M@60,rotate=90
video=DPI-1:480x640M@60,rotate=180
video=DPI-1:480x640M@60,rotate=270
display_rotate=1
sudo raspivid -t 0 -cs 0
libcamera-hello --list-cameras
libcamera-hello --camera 0
libcamera-jpeg -o test.jpg
</syntaxhighlight>

== Notes and version constraints ==
* The exact firmware version of the CM4 must be confirmed before configuration, as steps differ per OS.
* When running DPI and HDMI displays simultaneously, the rotation setting is shared; independent rotation is not possible.
* If i2cdetect fails, check whether dtparam -audio - on is blocked and whether /boot/dt-blob.bin exists.
* Unplugging or plugging any device other than USB and network ports while charging is prohibited.
* If a device is not recognized by the official image, a recompiled kernel module may be required.
* Exact compatibility of specific M.2 adapter cards depends on the individual device and may require manual adjustments.

== Source and revision record ==
* [https://www.waveshare.com/wiki/CM4-DISP-BASE-2.8A CM4-DISP-BASE-2.8A - Waveshare Wiki]
* Source revision: 109954
* Captured: 2026-09-03T02:50:13+00:00
* SHA-256: <code>d2b5caa83de515f6d994c80e29cfe6cf7a978451c8e8006cb87948f80a430c5c</code>