MCP23008

Arduino library for MCP23008 8 channel I2C port expander.

Description

This library gives easy control over the 8 pins of a (I2C) MCP23008 chip.

This IC is strongly related tot the MCP23017 I2C port expander - https://github.com/RobTillaart/MCP23017_RT Programming Interface is kept the same as much as possible.

Since 0.1.1 the digitalWrite(pin, value) is optimized. If a pin is not changed it will not be written again to save time.

0.3.0 Breaking change

The version 0.3.0 has breaking changes in the interface. The rationale is that the programming environment of the Arduino ESP32 S3 board uses a remapping by means of the include file io_pin_remap.h. This file remaps the pins of several core Arduino functions. The remapping is implemented by #define macros and these implement "hard" text replacements without considering context. The effect is that methods from this class (and several others) which have the same name as those Arduino core functions will be remapped into something not working.

The following library functions have been renamed:

old name	new name	notes
analogRead()	read()
analogWrite()	write()
pinMode()	pinMode1()
digitalRead()	read1()
digitalWrite()	write1()

0.2.0 Breaking change

Version 0.2.0 introduced a breaking change. You cannot set the pins in begin() any more. This reduces the dependency of processor dependent Wire implementations. The user has to call Wire.begin() and can optionally set the Wire pins before calling begin().

Related

16 bit port expanders

• https://github.com/RobTillaart/MCP23017_RT
• https://github.com/RobTillaart/MCP23S17
• https://github.com/RobTillaart/PCF8575
• https://github.com/RobTillaart/TCA9555

8 bit port expanders

• https://github.com/RobTillaart/MCP23008
• https://github.com/RobTillaart/MCP23S08
• https://github.com/RobTillaart/PCF8574

I2C

Supports 100kHz, 400kHz and 1.7MHz

TODO - add performance data

I2C multiplexing

Sometimes you need to control more devices than possible with the default address range the device provides. This is possible with an I2C multiplexer e.g. TCA9548 which creates up to eight channels (think of it as I2C subnets) which can use the complete address range of the device.

Drawback of using a multiplexer is that it takes more administration in your code e.g. which device is on which channel. This will slow down the access, which must be taken into account when deciding which devices are on which channel. Also note that switching between channels will slow down other devices too if they are behind the multiplexer.

• https://github.com/RobTillaart/TCA9548

Interface

#include "MCP23008.h"

Constructor

• MCP23008(uint8_t address, TwoWire *wire = &Wire) constructor, with default Wire interface.
  Can be overruled with Wire0..WireN.
• bool begin(bool pullup = true) initializes library, returns true if successful. Default sets the pins to INPUT PULLUP. Returns false if not connected or a register could not be set.
• bool isConnected() returns true if connected, false otherwise.
• uint8_t getAddress() returns address set in the constructor.

Single pin interface

• bool pinMode1(uint8_t pin, uint8_t mode) pin = 0..7, mode = INPUT, OUTPUT or INPUT_PULLUP. Do NOT use 0, 1 for mode as the 3 constants are (possibly) defined differently. Returns true if successful.
• bool write1(uint8_t pin, uint8_t value) pin = 0..7, value = LOW(0) HIGH (!0). Returns true if successful.
• uint8_t read1(uint8_t pin) pin = 0..7, returns LOW or HIGH, might set the lastError();
• bool setPolarity(uint8_t pin, bool reversed) pin = 0..7, set reversed flag. Returns true if successful.
• bool getPolarity(uint8_t pin, bool &reversed) pin = 0..7, reads reversed flag. Returns true if successful.
• bool setPullup(uint8_t pin, bool pullup) pin = 0..7, set pull-up flag. Returns true if successful.
• bool getPullup(uint8_t pin, bool &pullup) pin = 0..7, reads pull-up flag. Returns true if successful.

8 pins interface

• bool pinMode8(uint8_t mask) mask = 0..255. Returns true if successful.
• bool write8(uint8_t value) value = 0..255. Returns true if successful.
• uint8_t read8() reads 8 pins into one byte.
• bool setPolarity8(uint8_t mask) sets polarity for 8 channels at once. Returns true if successful.
• bool getPolarity8(uint8_t &mask) reads polarity of 8 channels at once. Returns true if successful.
• bool setPullup8(uint8_t mask) sets pull-up for 8 channels at once. Returns true if successful.
• bool getPullup8(uint8_t &mask) reads pull-up for 8 channels at once. Returns true if successful.

Interrupts (experimental 0.3.3)

Read the datasheet for the details. Page 21.
Note: Error handling is limited.

pin = 0..7
mode = { RISING, FALLING, CHANGE }

• bool enableInterrupt(uint8_t pin, uint8_t mode) Returns true if successful. Returns MCP23017_PIN_ERROR if pin > 7.
• bool disableInterrupt(uint8_t pin) Returns true if successful. Returns MCP23017_PIN_ERROR if pin > 7.

Determine which pins caused the Interrupt. (datasheet).

• uint8_t getInterruptFlagRegister() Reads all 8 pins.

• uint8_t getInterruptCaptureRegister() Reads all 8 pins. Is used to detect if multiple pins triggered an interrupt.

• bool setInterruptPolarity(uint8_t ipol) polarity: 0 = LOW, 1 = HIGH, 2 = NONE/ODR

• uint8_t getInterruptPolarity() return set value.

IO Control Register

The library supports setting bit fields in the IO control register. Read the datasheet carefully!

• bool enableControlRegister(uint8_t mask) set IOCR bit fields
• bool disableControlRegister(uint8_t mask) clear IOCR bit fields

constant	mask	description
MCP23x17_IOCR_BANK	0x80	Controls how the registers are addressed.
MCP23x17_IOCR_MIRROR	0x40	INT Pins Mirror bit.
MCP23x17_IOCR_SEQOP	0x20	Sequential Operation mode bit.
MCP23x17_IOCR_DISSLW	0x10	Slew Rate control bit for SDA output.
MCP23x17_IOCR_HAEN	0x08	Hardware Address Enable bit (MCP23S17 only).
MCP23x17_IOCR_ODR	0x04	Configures the INT pin as an open-drain output.
MCP23x17_IOCR_INTPOL	0x02	This bit sets the polarity of the INT output pin.
MCP23x17_IOCR_NI	0x01	Not implemented.

Two dedicated functions are added: (MCP23S17 only)

• bool enableHardwareAddress() set IOCR_HAEN bit.
• bool disableHardwareAddress() clear IOCR_HAEN bit.

Error codes

If one of the above functions return false, there might be an error.

• int lastError() Above functions set an error flag that can be read with this function.
  Reading it will reset the flag to MCP23008_OK.

name	value	description
MCP23008_OK	0x00	No error
MCP23008_PIN_ERROR	0x81
MCP23008_I2C_ERROR	0x82	(compatibility)
MCP23008_VALUE_ERROR	0x83
MCP23008_PORT_ERROR	0x84
MCP23008_REGISTER_ERROR	0xFF	low level.
MCP23008_INVALID_READ	0xFF	low level.

Future

Must

• improve documentation

Should

• keep in sync with MCP23017

Could

Wont

Support

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Thank you,