Arduino library for MCP23017 16 channel I2C port expander.

This library gives easy control over the 16 pins of a (I2C) MCP23017 chip.

This IC is strongly related tot the MCP23S17 SPI port expander - https://github.com/RobTillaart/MCP23S17 Programming Interface is kept the same as much as possible.

The write1(pin, value) is optimized. If a pin is not changed it will not be written again to save time.

The I2C IO expander MCP23017 has changed according to the new data sheet. It is now a 14/16-bit IO expander. The pins GPA7 (7) and GPB7 (15) have lost their input mode, output mode still works. The chips look the same and did not change names. This implies it not possible to read 8 bits in parallel at the exact same moment any more. The REV D version now need reading both A and B register to get 8 bits parallel (with a minor delay).

Some details see:

• https://hackaday.com/2023/02/03/mcp23017-went-through-shortage-hell-lost-two-inputs/
• https://ww1.microchip.com/downloads/aemDocuments/documents/APID/ProductDocuments/DataSheets/MCP23017-Data-Sheet-DS20001952.pdf
• https://microchip.my.site.com/s/article/GPA7---GPB7-Cannot-Be-Used-as-Inputs-In-MCP23017
• https://www.elektormagazine.com/articles/breakout-board-mcp23017 (comment)
• https://forums.raspberrypi.com/viewtopic.php?t=91209&sid=f8c6df7c8ede76937a66503edfe25394

Note: the library has no provisions (yet) for detecting DEV D chips or handle them in a special way. There is an idea to implement a derived class MCP23017_REVD that provides automatic support. However low prio.

Note that the MCP23S017 (SPI version) does not have this "feature" for GPA7 and GPB7.

The version 0.6.0 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:

Version 0.5.0 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().

Supports 100kHz, 400kHz and 1.7MHz

TODO - add performance data

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

#include "MCP23017.h"

• MCP23017(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.

Please note REVD remarks at top.

• bool pinMode1(uint8_t pin, uint8_t mode) pin = 0..15, mode = INPUT, OUTPUT. Returns true if successful.
• bool write1(uint8_t pin, uint8_t value) pin = 0..15, value = LOW(0) HIGH (!0). Returns true if successful.
• uint8_t read1(uint8_t pin) pin = 0..15, returns LOW or HIGH, might set the lastError();
• bool setPolarity(uint8_t pin, bool reversed) pin = 0..15, set reversed flag. Returns true if successful.
• bool getPolarity(uint8_t pin, bool &reversed) pin = 0..15, reads reversed flag. Returns true if successful.
• bool setPullup(uint8_t pin, bool pullup) pin = 0..15, set pull-up flag. Returns true if successful.
• bool getPullup(uint8_t pin, bool &pullup) pin = 0..15, reads pull-up flag. Returns true if successful.

Please note REVD remarks at top.

• bool pinMode8(uint8_t port, uint8_t value) port = 0..1, value = 0..255. Returns true if successful.
• bool write8(uint8_t port, uint8_t value) port = 0..1, value = 0..255. Returns true if successful.
• uint8_t read8(uint8_t port) port = 0..1, reads 8 pins into one byte.
• bool setPolarity8(uint8_t port, uint8_t mask) port = 0..1, sets polarity for 8 channels at once. Returns true if successful.
• bool getPolarity8(uint8_t port, uint8_t &mask) port = 0..1, reads polarity of 8 channels at once. Returns true if successful.
• bool setPullup8(uint8_t port, uint8_t mask) port = 0..1, sets pull-up for 8 channels at once. Returns true if successful.
• bool getPullup8(uint8_t port, uint8_t &mask) port = 0..1, reads pull-up for 8 channels at once. Returns true if successful.

Please note REVD remarks at top.

• bool pinMode16(uint16_t value) value = 0..0xFFFF. Returns true if successful.
• bool write16(uint16_t value) value = 0..0xFFFF. Returns true if successful.
• uint16_t read16() reads 16 pins into an uint16_t.
• bool setPolarity16(uint16_t mask) sets polarity for 16 channels. Returns true if successful.
• bool getPolarity16(uint16_t &mask) reads polarity of 16 channels. Returns true if successful.
• bool setPullup16(uint16_t mask) sets pull-up for 16 channels. Returns true if successful.
• bool getPullup16(uint16_t &mask) reads pull-up for 16 channels. Returns true if successful.

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 MCP23017_OK.

• Improve and extend documentation
• add examples

• extend error codes
• optimize code - squeeze footprint
• investigate if REV D chips can be detected.

• initial value (16 bit?) as begin parameter (breaking change)
  • depends on input output pull-up etc
• investigate auto address increment
• create a derived class MCP23017_REVD

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