Quelltext der Seite 9904 – 3.5inch RPi LCD (A)/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 3.5inch RPi LCD (A) is a 3.5-inch resistive touch display with a 480 × 320 resolution and an SPI interface connected via the Raspberry Pi's GPIO header. It is physically sized to plug directly onto a Raspberry Pi 3/4/5.

== Related products at JW Tech ==
* [https://shop.jw-tech.eu/p/9904 9904 – 3.5inch Resistive Touch Display (A) for Raspberry Pi, 480 × 320, SPI Interface]
* [https://shop.jw-tech.eu/p/WSAL9904 WSAL9904 – 3.5inch Resistive Touch Display (A) for Raspberry Pi, 480 × 320, SPI Interface]

== Technical overview ==
* Resolution: 480 × 320 pixels
* Interface: SPI via the display's 26-pin connector; the Raspberry Pi provides 40 GPIO pins
* Connection: The display connector plugs into the GPIO header; pin mapping must be observed
* Pin 11 (TP_IRQ): Touch panel interrupt, low level when touched
* Pins 19 and 23 are shared between LCD and touch panel (LCD_SI/TP_SI and LCD_SCK/TP_SCK)
* Pins 24 and 26 are chip-select signals for the LCD and touch panel respectively
* Compatibility: Works with all Raspberry Pi versions
* Operating current approximately 150 mA; operating temperature range 0–70 °C (commercial grade)
* Supports FBCP software driver for setting software resolution and dual-screen display

'''Commands and examples – verify before use:''' 
<syntaxhighlight lang="text">
sudo apt-get install unzip -y
sudo apt-get install cmake -y
wget https://files.waveshare.com/wiki/common/Waveshare35a.zip
unzip ./Waveshare35a.zip
sudo cp waveshare35a.dtbo /boot/overlays/
sudo nano /boot/firmware/config.txt
dtparam=spi=on
dtoverlay=waveshare35a
hdmi_force_hotplug=1
max_usb_current=1
hdmi_group=2
hdmi_mode=87
hdmi_cvt 480 320 60 6 0 0 0
hdmi_drive=2
display_rotate=0
export FRAMEBUFFER=/dev/fb1
startx 2> /tmp/xorg_errors
sudo nano /usr/share/X11/xorg.conf.d/99-fbturbo.~
Section "Device"
Identifier "Allwinner A10/A13 FBDEV"
</syntaxhighlight>

== Notes and version constraints ==
* The source text contains placeholders such as &#123;&#123;&#123;name2&#125;&#125;&#125; and &#123;&#123;&#123;userDefinedInfo&#125;&#125;&#125;; these were ignored.
* Exact pin mappings must be verified during connection; incorrectly wired pins can cause malfunctions.
* Configuration varies by OS version (Trixie, Bookworm, Bullseye); steps are version-sensitive.
* Automatic CLI login requires the username to be 'pi'; otherwise auto-login will not work.
* After completing all configurations, system restart takes longer and SSH requires a moment before becoming available.
* If touch response is slow, the anti-jitter delay in the 99-calibration.conf file can be adjusted, but this may reduce touch accuracy.

== Source and revision record ==
* [https://www.waveshare.com/wiki/3.5inch_RPi_LCD_(A) 3.5inch RPi LCD (A) - Waveshare Wiki]
* Source revision: 107949
* Captured: 2026-08-29T09:54:45+00:00
* SHA-256: <code>7f3e49ec293a5c1dae5dae8c7ddc7cf9f1760456c8d2acc3732d24fe105e544c</code>