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# MCP23S08

Arduino library for MCP23S08 8 channel SPI port expander.


## Description

This experimental library gives easy control over the 8 pins of a (SPI) MCP23S08 chip.

This IC is strongly related to 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.


## Interface

### Constructor

- **MCP23S08(uint8_t select, uint8_t data, uint8_t clock)** constructor SW SPI.
- **MCP23S08(uint8_t select)** constructor HW SPI.
- **bool begin()** returns true if successful.
- **bool isConnected()** returns true if connected, false otherwise. (dummy)


### Single pin interface

- **bool pinMode(uint8_t pin, uint8_t mode)** pin = 0..7, mode = INPUT, OUTPUT. 
Returns true if successful.
- **bool digitalWrite(uint8_t pin, uint8_t value)** pin = 0..7, value = LOW(0) HIGH (!0). 
Returns true if successful.
- **uint8_t digitalRead(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 value)** value = 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.


### 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 **MCP23S08_OK**.

| NAME                    | VALUE  | DESCRIPTION |
|:------------------------|:------:|:------------|
| MCP23S08_OK             |  0x00  | No error    |
| MCP23S08_PIN_ERROR      |  0x81  |
| MCP23S08_SPI_ERROR      |  0x82  |
| MCP23S08_VALUE_ERROR    |  0x83  |
| MCP23S08_PORT_ERROR     |  0x84  |
| MCP23S08_REGISTER_ERROR |  0xFF  | low level.


## Operation

See examples.


## Future

#### must
- keep documentation in sync with MCP23S17

#### should
- keep functional in sync with MCP23017_RT and MCP23S17

#### could
- MCP23S17 sync
  - add enableIO controlRegister functions
  - add registers.h file