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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 Serial Expansion HAT adds two UART channels and eight programmable GPIOs to a compatible Raspberry Pi via an I2C interface. Addressing is set with the A0/A1 jumpers; the default setup is 3.3 V and address 0x48.

== Related products at JW Tech ==
* [https://shop.jw-tech.eu/p/WSAL15667 WSAL15667 – Serial Expansion HAT for Raspberry Pi, I2C Interface, 2-ch UART, 8 GPIOs]

== Technical overview ==
* Compatibility: Raspberry Pi Zero, Zero W, Zero WH, 2B, 3B, 3B+.
* Control chip: SC16IS752 (dual UART + 8 GPIO) over I2C.
* Operating voltage: 3.3 V; dimensions: 65 × 30 mm; mounting hole 3.0 mm.
* Default I2C address: 0x48 (A0 and A1 soldered to 3.3 V).
* Change the address by soldering 0 Ω resistors on A0/A1; the table lists 8-bit values, while the actual 7-bit address is obtained by right-shifting one bit.
* Status LEDs: PWR, TXDA, RXDA, TXDB, RXDB indicate channel state.
* Newer revisions (after 29 Dec 2021): the interrupt pin is configurable with resistors, allowing up to five stacked devices; older revisions (before 31 Dec 2019) hard-wire the interrupt to a fixed Pi GPIO.
* Multiple modules each need their own I2C address and, if needed, their own interrupt pin; more than five devices must be connected by cable.
* On Debian Bookworm only the lgpio library is available; bcm2835 and wiringPi are not installable there.
* Demo code in C and Python is available online; examples use a default baud rate of 115200.

'''Commands and examples – verify before use:'''
<syntaxhighlight lang="text">
sudo raspi-config
sudo reboot
sudo nano /boot/config.txt
dtoverlay=sc16is752-i2c,int_pin=24,addr=0x48
ls /dev
sudo apt-get install i2c-tools
sudo i2cdetect -y 1
dtoverlay=sc16is752-i2c,int_pin=23,addr=0x49
</syntaxhighlight>

== Notes and version constraints ==
* The exact hardware revision (old/new) determines whether the interrupt pin is hard-wired or resistor-switchable – verify before stacking.
* Under Ubuntu on the Pi, /boot/config.txt appears empty on the device; edit it via the SD card slot on a host computer.
* The I2C address table lists 8-bit values; the usable address is the value after a one-bit right shift (e.g., 0x90 → 0x48).
* Stacking beyond five devices requires additional cabling instead of jumpers.
* Availability of bcm2835/wiringPi depends heavily on the OS release; both are unavailable under Bookworm.
* Before testing external serial devices, GND must be connected.
* If the expected ttySC* entries do not appear, re-check addresses and interrupt pins with i2cdetect.

== Source and revision record ==
* [https://www.waveshare.com/wiki/Serial_Expansion_HAT Serial Expansion HAT - Waveshare Wiki]
* Source revision: 78040
* Captured: 2026-08-31T02:53:47+00:00
* SHA-256: <code>9ca9f19a9c260c876f0d3af93010fd113bd8e0e247ae56e6f57cd4d8b19c7a05</code>

WSAL15667 – Serial Expansion HAT/en - Versionsgeschichte

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