mcp23018.h

Helper module for controlling an MCP23018 I/O expander via I2C. Depends on the i2chelper.h module.

NOTE: If the macro MCP23018_BANK_MODE is defined, the I/O expander is assumed to operate in banked mode (i.e. all registers for the same I/O port are located together in the expander’s register address space). If MCP23018_BANK_MODE is NOT defined, the I/O expander is assumed to operate in paired mode (i.e. all registers of the same type are located together). Consult your expander’s datasheet for details on the different addressing modes.

Summary

mcp23018.h	Helper module for controlling an MCP23018 I/O expander via I2C.
Macros
MCP23018_MAX_PAIR	The largest valid register pair address.
MCP23018_MAX_BANK	The largest valid register bank address.
MCP23018_REG_MASK	Bit mask for the valid bits of an MCP23018 register address.
Enumerations
MCP23018 IOCON Bit Numbers	An MCP23018 can be reconfigured by setting these bits in the IOCON register.
MCP23018 Register Addresses	These registers are used to configure and perform I/O with an MCP23018 via I2C.
Variables
mcp23018_reg	The type of MCP23018 register addresses.
Functions
mcp23018_is_valid_reg	Register address validator.
mcp23018_begin_read	Starts an asynchronous register read operation.
mcp23018_poll_read	Tests whether there is an ongoing I2C operation.
mcp23018_read	Performs a synchronous register read operation.
mcp23018_begin_write	Starts an asynchronous register write operation.
mcp23018_write	Performs a synchronous register write operation.

Macros

MCP23018_MAX_PAIR

The largest valid register pair address. Constant macro.

MCP23018_MAX_BANK

The largest valid register bank address. Constant macro.

MCP23018_REG_MASK

Bit mask for the valid bits of an MCP23018 register address. Constant macro.

Enumerations

MCP23018 IOCON Bit Numbers

An MCP23018 can be reconfigured by setting these bits in the IOCON register.

MCP23018_INTCC	interrupt clearing control, 0: clear on GPIO read, 1: clear on INTCAP read
MCP23018_INTPOL	interrupt output polarity, 0: active-low, 1: active-high
MCP23018_ODR	open-drain interrupt output enable, 0: active driver, 1: open-drain
MCP23018_SEQOP	sequential operation disable, 0: address auto-incremented, 1: address retained
MCP23018_MIRROR	mirrored interrupt output enable, 0: outputs separate, 1: outputs mirrored
MCP23018_BANK	register bank mode enable, 0: registers paired, 1: registers in banks

MCP23018 Register Addresses

These registers are used to configure and perform I/O with an MCP23018 via I2C.

NOTE: The IODIRx registers are set to all ones (i.e. all inputs) on startup/reset. All other registers are zeroed on startup/reset.

NOTE: Entries where the register name ends with an ‘x’ describe two registers, one for the ‘A’ port and one for the ‘B’ port, named correspondingly.

MCP23018_IODIRx	[RW] I/O direction, 0: output, 1: input
MCP23018_IPOLx	[RW] input polarity, 0: same, 1: inverted
MCP23018_GPINTENx	[RW] interrupt trigger enable, 0: disabled, 1: enabled
MCP23018_DEFVALx	[RW] reference value for level-triggered interrupts
MCP23018_INTCONx	[RW] interrupt mode select, 0: edge-triggered, 1: level-triggered
MCP23018_IOCON	[RW] configuration register
MCP23018_GPPUx	[RW] I/O pull-up enable, 0: disabled, 1: enabled
MCP23018_INTFx	[R] interrupt flag register, 0: no interrupt, 1: interrupt pending
MCP23018_INTCAPx	[R] interrupt capture register
MCP23018_GPIOx	[RW] I/O port register
MCP23018_OLATx	[RW] output latch register
MCP23018_NOT_A_REG	guaranteed to NOT be a valid register address

Variables

mcp23018_reg

typedef uint8_t mcp23018_reg

The type of MCP23018 register addresses.

NOTE: Bits that are set to zero in MCP23018_REG_MASK are zero in all valid register addresses.

Functions

mcp23018_is_valid_reg

uint8_t mcp23018_is_valid_reg( mcp23018_reg r )

Parameters

r	A register address.

Returns

A true value if and only if the argument is a valid MCP23018 register address in the selected addressing mode (i.e. paired or banked).

mcp23018_begin_read

i2c_state mcp23018_begin_read( i2c_slave_addr addr,
mcp23018_reg r )

Starts an asynchronous register read operation. This function delegates to i2chelper_request and completion of the register read can be detected as described in the documentation of that function.

Parameters

addr	7-bit I2C slave address of the target device. The address MUST be stored in the 7 least significant bits of the argument and MUST NOT include an R/W control bit.
r	Address of the register to read.

Returns

I2C_ACTIVE if and only if the register read operation was successfully started, otherwise an error code.

mcp23018_poll_read

i2c_state mcp23018_poll_read( uint8_t * v )

Tests whether there is an ongoing I2C operation. If there is no ongoing operation, this function will output the most recently read MCP23018 register value.

CAUTION: This function does not check whether any MCP23018 register read operation has actually been started.

Parameters

v	Pointer to memory where the most recently read register value should be stored. This output parameter is updated only when the returned i2c_state is I2C_READY.

Returns

An i2c_state value representing the current state of the I2C module.

mcp23018_read

i2c_state mcp23018_read( i2c_slave_addr addr,
mcp23018_reg r,
uint8_t * v )

Performs a synchronous register read operation.

Parameters

addr	7-bit I2C slave address of the target device. The address MUST be stored in the 7 least significant bits of the argument and MUST NOT include an R/W control bit.
r	Address of the register to read.
v	Pointer to memory where the result of the read register operation should be stored. This output parameter is updated only when the returned i2c_state is I2C_READY.

Returns

I2C_READY if and only if the register read operation was successfully performed, otherwise an error code.

mcp23018_begin_write

i2c_state mcp23018_begin_write( i2c_slave_addr addr,
mcp23018_reg r,
uint8_t v )

Starts an asynchronous register write operation. This function delegates to i2chelper_request and completion of the register write can be detected as described in the documentation of that function.

Parameters

addr	7-bit I2C slave address of the target device. The address MUST be stored in the 7 least significant bits of the argument and MUST NOT include an R/W control bit.
r	Address of the register to write to.
v	Value to write to the target register.

Returns

I2C_ACTIVE if and only if the register read operation was successfully started, otherwise an error code.

mcp23018_write

i2c_state mcp23018_write( i2c_slave_addr addr,
mcp23018_reg r,
uint8_t v )

Performs a synchronous register write operation.

Parameters

addr	7-bit I2C slave address of the target device. The address MUST be stored in the 7 least significant bits of the argument and MUST NOT include an R/W control bit.
r	Address of the register to write to.
v	Value to write to the target register.

Returns

I2C_READY if and only if the register write operation was successfully performed, otherwise an error code.