I/O Expander with Level Shifter, 8-Ch, I2C, Qwiic

Electrokit EKM017 – 8-Channel I2C I/O Expander with Level Shifter (TCA6408A). The EKM017 is a port expander featuring eight GPIO channels, based on the Texas Instruments TCA6408A. The module communicates via the I2C bus and provides 8 configurable input/output channels.

Each channel can be set as either input or output, offering flexibility for various control and monitoring applications. Thanks to separate supply voltages for the I2C side (VCCi) and the I/O ports (VCCp), integrated level shifting between different logic levels (1.65–5.5 V) is enabled without requiring external level shifters.

The TCA6408A is particularly well-suited for systems where the main microcontroller has a limited number of GPIOs. Each port can directly drive LEDs with up to 10 mA (source) or 25 mA (sink). An interrupt output (INT) signals input state changes and can be used to trigger events without continuous I2C polling.

Two devices can be used on the same I2C bus thanks to address selection via solder jumper. The module is equipped with dual QWIIC-compatible connectors for fast and reliable connection.

Features:

• Add 8 GPIOs via I2C
• Each port configurable as input or output
• Integrated level shifter
• High load capability – direct control of e.g., LEDs
• QWIIC connectors for easy and quick connection

Specifications:

• Supply voltage VCCi: 1.65–5.5 VDC (I2C side)
• Supply voltage VCCp: 1.65–5.5 VDC (I/O ports)
• Max current per port: 25 mA (sink) / 10 mA (source)
• I2C speed: 100 kHz / 400 kHz
• I2C address: 0x20 (default) / 0x21 (via solder jumper)
• Dimensions: 26 × 18 mm
• Mounting holes: 21 mm c-c / Ø2.5 mm

Connections:

• VCCi / GND – Power for I²C side

• VCCp / GND – Power for I/O ports

• SDA / SCL – Serial data and clock for I²C communication

• RST – Reset input (active low)

• INT – Interrupt output – open-drain (active low)

• RST and INT have internal pull-up resistors to VCCi

• IO0 – IO7 – Eight I/O channels (default to input at startup)

When using the QWIIC connectors, VCCi and GND pins do not need to be connected separately. Pull-up resistors (10 kΩ) for SDA and SCL are mounted on the board and can be disconnected via solder jumpers on the back.

Conclusion:

The TCA6408A is an excellent choice for projects that require more GPIOs than are available on the primary microcontroller. The integrated level shifting makes the module particularly suitable for systems with mixed logic levels. With high reliability, simple integration, and competitive pricing, the EKM017 is a highly functional and versatile addition to any I²C-based system.