mcp23s17.h File Reference

A simple static library for controlling an MCP23S17 port expander over SPI. More...

#include <stdint.h>

Go to the source code of this file.

Macros
#define	WRITE_CMD   0
#define	READ_CMD   1
#define	IODIRA   0x00
#define	IODIRB   0x01
#define	IPOLA   0x02
#define	IPOLB   0x03
#define	GPINTENA   0x04
#define	GPINTENB   0x05
#define	DEFVALA   0x06
#define	DEFVALB   0x07
#define	INTCONA   0x08
#define	INTCONB   0x09
#define	IOCON   0x0A
#define	GPPUA   0x0C
#define	GPPUB   0x0D
#define	INTFA   0x0E
#define	INTFB   0x0F
#define	INTCAPA   0x10
#define	INTCAPB   0x11
#define	GPIOA   0x12
#define	GPIOB   0x13
#define	OLATA   0x14
#define	OLATB   0x15
#define	BANK_OFF   0x00
#define	BANK_ON   0x80
#define	INT_MIRROR_ON   0x40
#define	INT_MIRROR_OFF   0x00
#define	SEQOP_OFF   0x20
#define	SEQOP_ON   0x00
#define	DISSLW_ON   0x10
#define	DISSLW_OFF   0x00
#define	HAEN_ON   0x08
#define	HAEN_OFF   0x00
#define	ODR_ON   0x04
#define	ODR_OFF   0x00
#define	INTPOL_HIGH   0x02
#define	INTPOL_LOW   0x00
#define	GPIO_INTERRUPT_PIN   25

Functions
int	mcp23s17_open (int bus, int chip_select)
uint8_t	mcp23s17_read_reg (uint8_t reg, uint8_t hw_addr, int fd)
void	mcp23s17_write_reg (uint8_t data, uint8_t reg, uint8_t hw_addr, int fd)
uint8_t	mcp23s17_read_bit (uint8_t bit_num, uint8_t reg, uint8_t hw_addr, int fd)
void	mcp23s17_write_bit (uint8_t data, uint8_t bit_num, uint8_t reg, uint8_t hw_addr, int fd)
int	mcp23s17_enable_interrupts ()
int	mcp23s17_disable_interrupts ()
int	mcp23s17_wait_for_interrupt (int timeout)

Detailed Description

A simple static library for controlling an MCP23S17 port expander over SPI.

Datasheet: http://ww1.microchip.com/downloads/en/devicedoc/21952b.pdf

Copyright (C) 2013 Thomas Preston thoma.nosp@m.s.pr.nosp@m.eston.nosp@m.@ope.nosp@m.nlx.o.nosp@m.rg.u.nosp@m.k

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

Function Documentation

int mcp23s17_disable_interrupts

(

)

Disables interrupts and exports to the GPIO connection from the mcp23s17.

Returns

int 0 on success

int mcp23s17_enable_interrupts

(

)

Enables interrupts and exports to the GPIO connection from the mcp23s17.

Returns

int 0 on success

int mcp23s17_open	(	int	bus,
		int	chip_select
	)

Returns a file descriptor for the SPI device through which the MCP23S17 port expander can be accessed.

Parameters

bus	The SPI bus.
chip_select	The SPI chip select.

uint8_t mcp23s17_read_bit	(	uint8_t	bit_num,
		uint8_t	reg,
		uint8_t	hw_addr,
		int	fd
	)

Reads a single bit from the register specified. Must also specify which hardware address and file descriptor to use.

Parameters

bit_num	The bit number to read.
reg	The register to read from (example: IODIRA, GPIOA).
hw_addr	The hardware address of the MCP23S17.
fd	The file descriptor returned from <mcp23s17_open>"()".

uint8_t mcp23s17_read_reg	(	uint8_t	reg,
		uint8_t	hw_addr,
		int	fd
	)

Returns the 8 bit value from the register specified. Must also specify which hardware address and file descriptor to use.

Parameters

reg	The register to read from (example: IODIRA, GPIOA).
hw_addr	The hardware address of the MCP23S17.
fd	The file descriptor returned from <mcp23s17_open>"()".

int mcp23s17_wait_for_interrupt

(

int

timeout

)

Waits for an interrupt from the mcp23s17 or until timeout is reached.

Note

This method does NOT reset the interrupt - which is done automatically for you by reading the input state register. Calling this method twice in a row without reading the input register will cause it to always wait for your timeout value, regardless of button presses. To avoid this, read the input register after every call to this method.

Parameters

timeout

Maximum ms to wait for input, -1 for forever

Returns

the number of file descriptors ready for the requested I/O, zero if no file descriptor became ready during the requested timeout milliseconds, or -1 on error.

void mcp23s17_write_bit	(	uint8_t	data,
		uint8_t	bit_num,
		uint8_t	reg,
		uint8_t	hw_addr,
		int	fd
	)

Writes a single bit to the register specified. Must also specify which hardware address and file descriptor to use.

Parameters

data	The data to write.
bit_num	The bit number to write to.
reg	The register to write to (example: IODIRA, GPIOA).
hw_addr	The hardware address of the MCP23S17.
fd	The file descriptor returned from <mcp23s17_open>"()".

void mcp23s17_write_reg	(	uint8_t	data,
		uint8_t	reg,
		uint8_t	hw_addr,
		int	fd
	)

Writes an 8 bit value to the register specified. Must also specify which hardware address and file descriptor to use.

Parameters

data	The data byte to be written.
reg	The register to write to (example: IODIRA, GPIOA).
hw_addr	The hardware address of the MCP23S17.
fd	The file descriptor returned from <mcp23s17_open>"()".