IO expander hardware components

Applicable for

STM32MP13x lines, STM32MP15x lines

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1 Article purpose

The purpose of this article is to:

• list the I/O expanders hardware components that might be integrated in the different STM32MPU boards
• link these components to the corresponding software framework(s)
• point to the datasheet(s) of these components
• explain, when necessary, how to configure these components.

2 Software frameworks

Domain	Peripheral	Software components			Comment
		OP-TEE	Linux	STM32Cube
Core/I/Os	ST MFX (Multi-Function eXpander)		Linux IOs pins overview		I/O expander
Core/I/Os	MCP23017		Linux IOs pins overview		I/O expander

3 ST MFX (Multi-Function eXpander)

The ST MFX is an STM32L152 slave controller whose firmware embeds an I/O expander feature with 16 GPIOs + 8 GPIOs extra if other features (resistive touchscreen controller and IDD measurement) are not enabled.

For details, refer to UM2535, chapter MFX IO expander.

3.1 Linux driver

Bindings: Documentation/devicetree/bindings/mfd/st,stmfx.yaml

Sources:

• drivers/mfd/stmfx.c
• drivers/pinctrl/pinctrl-stmfx.c

4 MCP23017

The MCP23017 is a 16-bit input/output port expander with interrupt output.

For details and the datasheet please contact the MCP23017 I/O expander provider.

4.1 Linux driver

Bindings: Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt

Sources:

• drivers/pinctrl/pinctrl-mcp23s08.c
• drivers/pinctrl/pinctrl-mcp23s08_i2c.c