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326 lines
12 KiB
Markdown
326 lines
12 KiB
Markdown
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[](https://github.com/RobTillaart/MCP23S17/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/MCP23S17/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/MCP23S17/issues)
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[](https://github.com/RobTillaart/MCP23S17/blob/master/LICENSE)
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[](https://github.com/RobTillaart/MCP23S17/releases)
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[](https://registry.platformio.org/libraries/robtillaart/MCP23S17)
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# MCP23S17
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Arduino library for MCP23S17 16 channel SPI port expander.
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## Description
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This library gives easy control over the 16 pins of a (SPI) MCP23S17 chip.
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This IC is strongly related to 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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The **write1(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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#### 0.5.0 Breaking change
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Version 0.5.0 introduced a breaking change to improve handling the SPI dependency.
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The user has to call **SPI.begin()** or equivalent before calling **MCP.begin()**.
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Optionally the user can provide parameters to the **SPI.begin(...)**
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#### 0.4.0 Breaking change
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The version 0.4.0 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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#### 0.3.0 Breaking change
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The version 0.3.0 has breaking changes in the interface.
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The essence is removal of ESP32 specific code from the library.
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This makes it possible to support the ESP32-S3 and other processors in the future.
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Also it makes the library a bit simpler to maintain.
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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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## Interface
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```cpp
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#include "MCP23S17.h"
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```
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### Constructor
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- **MCP23S17(uint8_t select, uint8_t dataIn, uint8_t dataOut, uint8_t clock, uint8_t address = 0x00)** constructor SOFTWARE SPI.
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- **MCP23S17(int select, SPIClassRP2040\* spi)** constructor HARDWARE SPI with explicit SPI interface selected.
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- **MCP23S17(int select, SPIClass\* spi)** constructor HARDWARE SPI with explicit SPI interface selected.
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- **MCP23S17(int select, int address = 0x00, SPIClassRP2040\* spi = &SPI)** constructor HARDWARE SPI with optional address pins and SPI interface.
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- **MCP23S17(int select, int address = 0x00, SPIClass\* spi = &SPI)** constructor HARDWARE SPI with optional address pins and SPI interface.
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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. (dummy for compatibility reasons)
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- **uint8_t getAddress()** returns the address set in the constructor.
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Default = 0, range = 0..7.
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The two hardware constructors allow to call 4 different constructors.
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```cpp
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- MCP23S17(10); // select pin only
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- MCP23S17(10, 7); // select pin + address pins
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- MCP23S17(10, 7, &SPI2); // select pin + address pins + SPI port
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- MCP23S17(10, &SPI2); // select pin + SPI port
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```
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#### Sharing SELECT lines
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(verified in #19)
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Technically two chips could use the same SELECT pin and a different address.
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Since 0.2.5 the constructors allow to setup such a configuration.
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The added value is that one can use up to 8 devices (= 128 IO lines) with only
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four lines (MISO, MOSI, CLOCK, SELECT).
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I assume that this configuration is less used and IMHO not recommended.
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NB it is more difficult to detect which device is selected when debugging.
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To use the hardware addresses the Hardware Address ENable register must be set.
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See datasheet 3.3.2 ADDRESSING SPI DEVICES, need to set IOCON.HAEN.
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The library supports two ways:
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```cpp
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MCP.enableControlRegister(MCP23S17_IOCR_HAEN); // or 0x08
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or
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MCP.enableHardwareAddress(); // 0.2.5 version and up
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```
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See also **IO Control Register** section below.
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### Single pin interface
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- **bool pinMode1(uint8_t pin, uint8_t mode)** pin = 0..15, 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..15, value = LOW(0) HIGH (!0). Returns true if successful.
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- **uint8_t read1(uint8_t pin)** pin = 0..15, returns LOW or HIGH, might set the lastError();
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- **bool setPolarity(uint8_t pin, bool reversed)** pin = 0..15, set reversed flag. Returns true if successful.
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- **bool getPolarity(uint8_t pin, bool &reversed)** pin = 0..15, reads reversed flag. Returns true if successful.
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- **bool setPullup(uint8_t pin, bool pullup)** pin = 0..15, set pull-up flag. Returns true if successful.
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- **bool getPullup(uint8_t pin, bool &pullup)** pin = 0..15, reads pull-up flag. Returns true if successful.
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### 8 pins interface
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- **bool pinMode8(uint8_t port, uint8_t mask)** port = 0..1, mask = 0..255. Returns true if successful.
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- **bool write8(uint8_t port, uint8_t value)** port = 0..1, value = 0..255. Returns true if successful.
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- **uint8_t read8(uint8_t port)** port = 0..1, reads 8 pins into one byte.
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- **bool setPolarity8(uint8_t port, uint8_t mask)** port = 0..1, sets polarity for 8 channels at once.
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Returns true if successful.
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- **bool getPolarity8(uint8_t port, uint8_t &mask)** port = 0..1, reads polarity of 8 channels at once.
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Returns true if successful.
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- **bool setPullup8(uint8_t port, uint8_t mask)** port = 0..1, sets pull-up for 8 channels at once.
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Returns true if successful.
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- **bool getPullup8(uint8_t port, uint8_t &mask)** port = 0..1, reads pull-up for 8 channels at once.
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Returns true if successful.
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### 16 pins interface
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- **bool pinMode16(uint16_t mask)** mask = 0..0xFFFF, returns true if successful.
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- **bool write16(uint16_t value)** value = 0..0xFFFF, returns true if successful.
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- **uint16_t read16()** reads 16 pins into an uint16_t.
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- **bool setPolarity16(uint16_t mask)** sets polarity for 16 channels.
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Returns true if successful.
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- **bool getPolarity16(uint16_t &mask)** reads polarity of 16 channels.
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Returns true if successful.
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- **bool setPullup16(uint16_t mask)** sets pull-up for 16 channels.
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Returns true if successful.
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- **bool getPullup16(uint16_t &mask)** reads pull-up for 16 channels.
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Returns true if successful.
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The reading and writing to registers have been performance optimized for the 16 bit interface.
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If there are problems please open an issue.
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### Interrupts (experimental 0.5.2)
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Read the datasheet for the details, page 24,25.
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Note: Error handling is limited.
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pin = 0..15
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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 MCP23S17_PIN_ERROR if pin > 15.
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- **bool disableInterrupt(uint8_t pin)**
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Returns true if successful.
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Returns MCP23S17_PIN_ERROR if pin > 15.
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16 pin interface, overrides all earlier settings.
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Sets all pins to the same interrupt mode { RISING, FALLING, CHANGE }.
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- **bool enableInterrupt16(uint16_t mask, uint8_t mode)** mask = 0x0000..0xFFFF.
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- **bool disableInterrupt16(uint16_t mask)**
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Determine which pins caused the Interrupt. (datasheet).
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- **uint16_t getInterruptFlagRegister()** Reads all 16 pins.
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- **uint16_t getInterruptCaptureRegister()** Reads all 16 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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Merge INTA and INTB into one signal so only one line handles all interrupts.
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This reduces the number of interrupt lines to handle, however one has
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to read more registers to find the changed ones.
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- **bool mirrorInterrupts(bool on)** enables / disables mirror mode.
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- **bool isMirroredInterrupts()** returns set option (0,1 or 2).
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### SPI
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- **void setSPIspeed(uint32_t speed)** set hardware speed (8Mb default).
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- **uint32_t getSPIspeed()** returns set speed.
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### Debugging
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- **bool usesHWSPI()** returns true = hardware SPI, false = software SPI.
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- **int lastError()** idem.
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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 **MCP23S17_OK**.
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| name | value | description |
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|:--------------------------|:-------:|:--------------|
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| MCP23S17_OK | 0x00 | No error |
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| MCP23S17_PIN_ERROR | 0x81 |
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| MCP23S17_I2C_ERROR | 0x82 | (compatibility)
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| MCP23S17_VALUE_ERROR | 0x83 |
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| MCP23S17_PORT_ERROR | 0x84 |
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| MCP23S17_REGISTER_ERROR | 0xFF | low level.
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| MCP23S17_INVALID_READ | 0xFF | low level.
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## Future
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#### Must
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- Improve and extend documentation
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- add examples
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#### Should
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- keep functional in sync
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- sync error codes to MCP23x17
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- buy additional hardware
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- test with multiple devices.
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- multi SELECT lines
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- add example with interrupts
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- test
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- extend error codes
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- optimize code - squeeze footprint
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- fix TODO's in code
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- IOCON.HAEN, Hardware Address ENable.
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- should this be enabled in **begin()** by default? 0.3.0
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- check address range in constructor.
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#### Could
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- check need for writing in all functions (Polarity / Pull-up)
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- check if bit mask changes.
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- what is performance gain vs footprint?
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- investigate and reimplement the INPUT_PULLUP for pinMode() ?
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- initial value (16 bit?) as begin parameter (breaking change)
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- depends on input output pull-up etc
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- AVR software SPI optimize
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- dao and clock - see fastShiftOut.
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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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