What Is the PCF8575? 16-bit I2C I/O Expander and Uses
The PCF8575 is an I/O expander that adds 16 GPIO over I2C. It offers twice the pins of the 8-bit PCF8574; using just SDA/SCL it increases an MCU's pin count. It is used for button/LED/relay control and key matrices. It is quasi-bidirectional (weak high-drive on outputs); with the address pins up to 8 can share a bus.
The PCF8575 is an I/O expander that adds 16 GPIO pins over I2C. It offers twice the pins of the 8-bit PCF8574; using just SDA/SCL it increases an MCU's pin count. For the concept, see what is I2C.
What is the PCF8575 used for?
Controlling many buttons/LEDs/relays, key matrices and general pin expansion. It works quasi-bidirectionally like the PCF8574 (strong pull-low, weak pull-high). With the address pins (A0–A2) up to 8 can share one bus.
Specifications
| Parameter | Value |
|---|---|
| GPIO | 16 (P0–P17) |
| Interface | I2C |
| Extra | Interrupt (INT) output, A0–A2 addressing |
| Supply | 2.5–5.5 V |
Limitations
- Quasi-bidirectional; weak high-drive on outputs (good for sinking).
- Limited by I2C speed; for fast GPIO use a direct MCU pin.
Equivalents
- PCF8574: the 8-bit version.
- MCP23017: true bidirectional 16-bit.
- PCF8575C: a version with a different address.
Find it in our catalog
Use the PCF8575 search.