PCF8575 16-Channel GPIO Expander
16-channel I2C GPIO expander. Add 16 extra digital I/O pins. Quasi-bidirectional — each pin can be input or output.
Say it to PAL
“Turn on the light on pin 0.”
The code PAL writes
// There is no per-pin command: write_pins sets all 16 at once. Pins are active low, so
// clearing bit 0 sinks pin P00 and lights the LED; every other pin stays high.
p.write('qwiic-pcf8575', 'write_pins', { state: 0xFFFF & ~(1 << 0) });
p.log('LED on (active low)');“Read the button on pin 8.”
The code PAL writes
await p.write('qwiic-pcf8575', 'set_pin', { pin: 8, value: 1 });
const state = await p.read('qwiic-pcf8575', 'gpio');
const pin8 = (state >> 8) & 1;
p.log('Button: ' + (pin8 ? 'released' : 'pressed'));When to pick it
Use when you need more digital I/O pins than the Pi provides. 16 pins per board, chainable up to 128 pins.
Good to know
- Quasi-bidirectional pins have weak pull-ups (~300µA). External pull-ups may be needed for reliable input reading.
About it
The PCF8575 is a 16-bit I2C GPIO expander that provides 16 quasi-bidirectional I/O pins. Each pin can source/sink enough current to drive LEDs directly. Up to 8 expanders can be chained on one bus (addresses 0x20-0x27) for up to 128 extra I/O pins. The quasi-bidirectional design means pins default high (input) and are pulled low for output. No direction register needed — simply write a 0 to drive low or a 1 to release high (input/pulled up).
Where to buy
Facts
Tested
It is in our catalog, but nobody has checked it on a real board. It may not work yet. Its driver is written, but it has not been tested on hardware yet.
I2C address
0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27
The PCF8575 16-Channel GPIO Expander answers at I2C address 0x20. A jumper or pin moves it to 0x21 or 0x22 or 0x23 or 0x24 or 0x25 or 0x26 or 0x27.
Current
1 mA
The catalog lists a typical draw of 1 mA for the PCF8575 GPIO, copied from the maker’s description and not measured by Palpable.
Board size
40.64 × 17.78 mm
The PCF8575 GPIO board measures 40.64 × 17.78 mm and stands 4.5 mm tall with its parts. It has 4 mounting holes. These dimensions are from the maker’s mechanical drawing.
Chip
PCF8575
Its port expander is the NXP PCF8575.
Free to reuse
Every fact here is open data under CC BY 4.0. Copy it into your own docs or code, and credit Palpable. Download it
This record was last changed on October 6, 2026.