Configuration ⚙️

The driver can be configured programmatically or through Kconfig options. This section covers both approaches.

Runtime Configuration

The simplest method is to call the appropriate member functions at runtime:

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gpio.SetPinDirection(0, PACL95555::GPIODir::Output);
gpio.SetPullEnable(0, true);
gpio.SetPullDirection(0, true);  // true = pull-up

Runtime configuration gives you full flexibility and can be changed any time after initialization.

Kconfig Integration

For projects that use Kconfig (e.g. Zephyr, ESP-IDF) the library provides a set of options under the PCAL95555 menu. Important entries include:

  • PCAL95555_DEFAULT_ADDRESS – I²C address of the expander
  • PCAL95555_INIT_FROM_KCONFIG – automatically apply configuration at startup
  • Pin submenus – specify direction, pull mode and initial level for each pin

Call InitFromConfig() during startup to apply the selected values.

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PACL95555 gpio(&i2c, CONFIG_PCAL95555_DEFAULT_ADDRESS);
gpio.InitFromConfig();

A minimal Kconfig snippet might look like:

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config PCAL95555_DEFAULT_ADDRESS
    hex "Expander address"
    default 0x20

config PCAL95555_INIT_FROM_KCONFIG
    bool "Initialize expander at startup"
    default y

Use menuconfig or your build system’s configuration tool to adjust these values.

Adjust Kconfig to match your hardware setup. Refer to the Hardware Overview for pin capabilities.

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