This package provide methods for controlling GPIO pins, I2C and SPI buses.
This is written for A20-Lime, but it can be used with other boards. If you do
this we cannot guarantee proper operation of the module. Before using this
package we recommend reading the article at olimex wiki:

https://www.olimex.com/wiki/A20-OLinuXino-LIME

When using GPIO make sure that the desired gpio is not used by another periphery.

GPIO METHODS
============

    init()      -   Make initialization of the module. Always must be called first.
    getcfg()    -   Read current configuration of gpio.
    setcfg()    -   Write configuration to gpio.
    input()     -   Return current value of gpio.
    output()    -   Set output value.
    pullup()    -   Set pull-up/pull-down.


The available constants are:

    NAME        -   EQUALS TO
    ====            =========
    HIGH        ->      1
    LOW         ->      0
    INPUT       ->      0
    OUPTUT      ->      1
    PER         ->      2
    PULLNONE    ->      0
    PULLUP      ->      1
    PULLDOWN    ->      2


The gpio are named two ways:

    By port name: PH0, PG2, PE10, etc.
    These can be imported from gpio module:

    >>> from pySUNXI import gpio
    >>> dir(gpio)

Generally these constants are just an offset in the memory from the base GPIO address, so they can
be assigned to a number type variable.

    >>> led = gpio.PH(2)
    >>> print led
    226



I2C METHODS
===========

    init()      -   Make initialization of the module
    open()      -   Begin communication with slave device
    read()      -   Read from slave device
    write()     -   Write data to slave device
    close()     -   End communication with slave device


SPI METHODS
===========

    open()      -   Open SPI bus with given configuration
    read()      -   Read data from slave device without write
    write()     -   Write data to slave device without read
    xfer()      -   Do write and after that read
    close()     -   Close SPI bus



Examples
========

GPIO::

    #!/usr/bin/env python

    from pySUNXI import gpio

    gpio.init() #Initialize module. Always called first

    gpio.setcfg(gpio.PG(9), gpio.OUTPUT)  #Configure LED1 as output
    gpio.setcfg(gpio.PG(9), 1)    #This is the same as above

    gpio.setcfg(gpio.PE(11), gpio.INPUT)   #Configure PE11 as input
    gpio.setcfg(gpio.PE(11), 0)   #Same as above

    gpio.pullup(gpio.PE(11), gpio.PULLNONE)    #Clear pullups
    gpio.pullup(gpio.PE(11), gpio.PULLDOWN)    #Enable pull-down
    gpio.pullup(gpio.PE(11), gpio.PULLUP)  #Enable pull-up

    while True:
        if gpio.input(gpio.PE(11)) == 1:
            gpio.output(gpio.PG(9), gpio.LOW)
            gpio.output(gpio.PG(9), 0)
        else:
            gpio.output(gpio.PG(9), gpio.HIGH)
            gpio.output(gpio.PG(9), 1)


I2C::

    #!/usr/bin/env python

    from pySUNXI import i2c

    i2c.init("/dev/i2c-2")  #Initialize module to use /dev/i2c-2
    i2c.open(0x55)  #The slave device address is 0x55

    #If we want to write to some register
    i2c.write([0xAA, 0x20]) #Write 0x20 to register 0xAA
    i2c.write([0xAA, 0x10, 0x11, 0x12]) #Do continuous write with start address 0xAA

    #If we want to do write and read
    i2c.write([0xAA])   #Set address at 0xAA register
    value = i2c.read(1) #Read 1 byte with start address 0xAA

    i2c.close() #End communication with slave device


SPI::

    #!/usr/bin/env python

    from pySUNXI import spi

    spi.open("/dev/spidev2.0")
    #Open SPI device with default settings
    # mode : 0
    # speed : 100000kHz
    # delay : 0
    # bits-per-word: 8

    #Different ways to open device
    spi.open("/dev/spidev2.0", mode=1)
    spi.open("/dev/spidev2.0", mode=2, delay=0)
    spi.open("/dev/spidev2.0", mode=3, delay=0, bits_per_word=8)
    spi.open("/dev/spidev2.0", mode=0, delay=0, bits_per_word=8, speed=100000)

    spi.write([0x01, 0x02]) #Write 2 bytes to slave device
    spi.read(2) #Read 2 bytes from slave device
    spi.xfer([0x01, 0x02], 2)   #Write 2 byte and then read 2 bytes.

    spi.close() #Close SPI bus


It's important that you run your python script as root!