A demo of the AW9523 I2C GPIO expander for RP2040. The library is ported from the Adafruit Library for this; I've removed the Adafruit_I2CRegister abstraction provided by Adafruit_BusIO and just used raw Pico SDK i2c commands.
Currently this is configured for a pico_w in CMakeLists.txt; you should probably change that to pico for a regular board. I just had a Pico W on hand to test this with.
Connect an AW9523 over I2C, connecting SDA/SCL to GPIO4/5, respectively.
Connect pullups (around 4k7/5k6) between SDA/SCL and VCC.
Connect a push button between VCC and AW9523 pin 8. Connect a pull-up resistor between pin 8 and VCC.
Connect the cathodes of four LEDs to AW9523 IOs 1-4. Connect the anode to VCC. You do not need resistors.
Connect AW9523 VDD to 3V3, and GND to Ground.
By default, the demo will light LEDs on pins 1-4 at about 25% brightness.
Push the button to toggle to pulsing them through all brightnesses; each LED will be 90º out of phase, creating a scrolling effect. (I wouldn't recommend using floating point math and sin in a production object, but it'll do for our demo).
You need aw9523.cpp and aw9523.h included in your project via CMake, and then you'll be able to use and instantiate the library.