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236 lines
8.7 KiB
Markdown
236 lines
8.7 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/MCP23008/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/MCP23008/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/MCP23008/issues)
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[](https://github.com/RobTillaart/MCP23008/blob/master/LICENSE)
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[](https://github.com/RobTillaart/MCP23008/releases)
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[](https://registry.platformio.org/libraries/robtillaart/MCP23008)
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# MCP23008
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Arduino library for MCP23008 8 channel I2C port expander.
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## Description
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This library gives easy control over the 8 pins of a (I2C) MCP23008 chip.
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This IC is strongly related tot the MCP23017 I2C port expander - https://github.com/RobTillaart/MCP23017_RT
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Programming Interface is kept the same as much as possible.
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Since 0.1.1 the **digitalWrite(pin, value)** is optimized.
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If a pin is not changed it will not be written again to save time.
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#### 0.3.0 Breaking change
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The version 0.3.0 has breaking changes in the interface.
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The rationale is that the programming environment of the **Arduino ESP32 S3**
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board uses a remapping by means of the include file **io_pin_remap.h**.
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This file remaps the pins of several core Arduino functions.
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The remapping is implemented by #define macros and these implement "hard" text
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replacements without considering context.
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The effect is that methods from this class (and several others) which have the same
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name as those Arduino core functions will be remapped into something not working.
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The following library functions have been renamed:
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| old name | new name | notes |
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|:-----------------|:-------------|:--------|
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| analogRead() | read() |
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| analogWrite() | write() |
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| pinMode() | pinMode1() |
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| digitalRead() | read1() |
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| digitalWrite() | write1() |
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#### 0.2.0 Breaking change
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Version 0.2.0 introduced a breaking change.
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You cannot set the pins in **begin()** any more.
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This reduces the dependency of processor dependent Wire implementations.
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The user has to call **Wire.begin()** and can optionally set the Wire pins
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before calling **begin()**.
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#### Related
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16 bit port expanders
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- https://github.com/RobTillaart/MCP23017_RT
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- https://github.com/RobTillaart/MCP23S17
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- https://github.com/RobTillaart/PCF8575
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- https://github.com/RobTillaart/TCA9555
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8 bit port expanders
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- https://github.com/RobTillaart/MCP23008
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- https://github.com/RobTillaart/MCP23S08
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- https://github.com/RobTillaart/PCF8574
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## I2C
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Supports 100kHz, 400kHz and 1.7MHz
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TODO - add performance data
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#### I2C multiplexing
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Sometimes you need to control more devices than possible with the default
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address range the device provides.
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This is possible with an I2C multiplexer e.g. TCA9548 which creates up
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to eight channels (think of it as I2C subnets) which can use the complete
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address range of the device.
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Drawback of using a multiplexer is that it takes more administration in
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your code e.g. which device is on which channel.
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This will slow down the access, which must be taken into account when
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deciding which devices are on which channel.
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Also note that switching between channels will slow down other devices
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too if they are behind the multiplexer.
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- https://github.com/RobTillaart/TCA9548
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## Interface
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```cpp
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#include "MCP23008.h"
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```
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### Constructor
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- **MCP23008(uint8_t address, TwoWire \*wire = &Wire)** constructor, with default Wire interface.
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Can be overruled with Wire0..WireN.
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- **bool begin(bool pullup = true)** initializes library, returns true if successful.
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Default sets the pins to INPUT PULLUP.
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Returns false if not connected or a register could not be set.
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- **bool isConnected()** returns true if connected, false otherwise.
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- **uint8_t getAddress()** returns address set in the constructor.
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### Single pin interface
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- **bool pinMode1(uint8_t pin, uint8_t mode)** pin = 0..7, mode = INPUT, OUTPUT or INPUT_PULLUP.
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Do NOT use 0, 1 for mode as the 3 constants are (possibly) defined differently.
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Returns true if successful.
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- **bool write1(uint8_t pin, uint8_t value)** pin = 0..7, value = LOW(0) HIGH (!0). Returns true if successful.
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- **uint8_t read1(uint8_t pin)** pin = 0..7, returns LOW or HIGH, might set the lastError();
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- **bool setPolarity(uint8_t pin, bool reversed)** pin = 0..7, set reversed flag. Returns true if successful.
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- **bool getPolarity(uint8_t pin, bool &reversed)** pin = 0..7, reads reversed flag. Returns true if successful.
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- **bool setPullup(uint8_t pin, bool pullup)** pin = 0..7, set pull-up flag. Returns true if successful.
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- **bool getPullup(uint8_t pin, bool &pullup)** pin = 0..7, reads pull-up flag. Returns true if successful.
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### 8 pins interface
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- **bool pinMode8(uint8_t mask)** mask = 0..255. Returns true if successful.
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- **bool write8(uint8_t value)** value = 0..255. Returns true if successful.
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- **uint8_t read8()** reads 8 pins into one byte.
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- **bool setPolarity8(uint8_t mask)** sets polarity for 8 channels at once. Returns true if successful.
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- **bool getPolarity8(uint8_t &mask)** reads polarity of 8 channels at once. Returns true if successful.
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- **bool setPullup8(uint8_t mask)** sets pull-up for 8 channels at once. Returns true if successful.
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- **bool getPullup8(uint8_t &mask)** reads pull-up for 8 channels at once. Returns true if successful.
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### Interrupts (experimental 0.3.3)
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Read the datasheet for the details. Page 21.
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Note: Error handling is limited.
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pin = 0..7
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mode = { RISING, FALLING, CHANGE }
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- **bool enableInterrupt(uint8_t pin, uint8_t mode)**
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Returns true if successful.
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Returns MCP23017_PIN_ERROR if pin > 7.
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- **bool disableInterrupt(uint8_t pin)**
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Returns true if successful.
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Returns MCP23017_PIN_ERROR if pin > 7.
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Determine which pins caused the Interrupt. (datasheet).
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- **uint8_t getInterruptFlagRegister()** Reads all 8 pins.
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- **uint8_t getInterruptCaptureRegister()** Reads all 8 pins.
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Is used to detect if multiple pins triggered an interrupt.
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- **bool setInterruptPolarity(uint8_t ipol)** polarity: 0 = LOW, 1 = HIGH, 2 = NONE/ODR
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- **uint8_t getInterruptPolarity()** return set value.
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### IO Control Register
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The library supports setting bit fields in the IO control register.
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Read the datasheet carefully!
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- **bool enableControlRegister(uint8_t mask)** set IOCR bit fields
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- **bool disableControlRegister(uint8_t mask)** clear IOCR bit fields
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| constant | mask | description |
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|:-----------------------|:------:|:--------------|
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| MCP23x17_IOCR_BANK | 0x80 | Controls how the registers are addressed.
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| MCP23x17_IOCR_MIRROR | 0x40 | INT Pins Mirror bit.
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| MCP23x17_IOCR_SEQOP | 0x20 | Sequential Operation mode bit.
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| MCP23x17_IOCR_DISSLW | 0x10 | Slew Rate control bit for SDA output.
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| MCP23x17_IOCR_HAEN | 0x08 | Hardware Address Enable bit (MCP23S17 only).
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| MCP23x17_IOCR_ODR | 0x04 | Configures the INT pin as an open-drain output.
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| MCP23x17_IOCR_INTPOL | 0x02 | This bit sets the polarity of the INT output pin.
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| MCP23x17_IOCR_NI | 0x01 | Not implemented.
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Two dedicated functions are added: (MCP23S17 only)
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- **bool enableHardwareAddress()** set IOCR_HAEN bit.
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- **bool disableHardwareAddress()** clear IOCR_HAEN bit.
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### Error codes
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If one of the above functions return false, there might be an error.
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- **int lastError()** Above functions set an error flag that can be read with this function.
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Reading it will reset the flag to **MCP23008_OK**.
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| name | value | description |
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|:--------------------------|:-------:|:--------------|
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| MCP23008_OK | 0x00 | No error |
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| MCP23008_PIN_ERROR | 0x81 |
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| MCP23008_I2C_ERROR | 0x82 | (compatibility)
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| MCP23008_VALUE_ERROR | 0x83 |
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| MCP23008_PORT_ERROR | 0x84 |
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| MCP23008_REGISTER_ERROR | 0xFF | low level.
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| MCP23008_INVALID_READ | 0xFF | low level.
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## Future
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#### Must
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- improve documentation
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#### Should
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- keep in sync with MCP23017
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#### Could
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#### Wont
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## Support
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If you appreciate my libraries, you can support the development and maintenance.
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Improve the quality of the libraries by providing issues and Pull Requests, or
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donate through PayPal or GitHub sponsors.
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Thank you,
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