pyA20 0.2.12

Control GPIO, I2C and SPI on A20-OLinuXino-MICRO

Description

The package provide methods for controlling GPIO pins, I2C and SPI buses. It’s written for A20-OLinuXino-MICRO, but it can be used with other boards. In this case proper operation is not guaranteed. You can check wiki for more information.

Notes:

• When using GPIO make sure that the desired gpio is not used by another periphery.
• Using this library requires root access.

GPIO methods

The following methods are available:

• init() - Make initialization of the module. 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:

• HIGH - 1
• LOW - 0
• INPUT - 0
• OUPTUT - 1
• PULLUP - 1
• PULLDOWN - 2

The gpio are named two ways:

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

>>> from pyA20.gpio import port
>>> dir(port)

• By connector name and pin number: gpio2p12, gpio3p8, lcdp18, uext1p3 and etc:

>>> from pyA20.gpio import connector
>>> dir(connector)

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 = port.PH2
>>> 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

The example consist of: * Initialize gpio module * Initialize one gpio as output and another one as input * Polling input state and write corresponding output value

#!/usr/bin/env python

from pyA20.gpio import gpio
from pyA20.gpio import port
from pyA20.gpio import connector

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

gpio.setcfg(port.PG9, gpio.OUTPUT)  #Configure LED1 as output
gpio.setcfg(port.PG9, 1)    #This is the same as above

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

gpio.pullup(port.PE11, 0)   #Clear pullups
gpio.pullup(port.PE11, gpio.PULLDOWN)    #Enable pull-down
gpio.pullup(port.PE11, gpio.PULLUP)  #Enable pull-up

while True:
        if gpio.input(port.PE11) == 1:
                gpio.output(port.PG9, gpio.LOW)
                gpio.output(port.PG9, 0)
        else:
                gpio.output(port.PG9, gpio.HIGH)
                gpio.output(port.PG9, 1)

I2C

In this example: * I2C module is imported * Bus number 2 is opened * Some data is written, then verified

#!/usr/bin/env python

from pyA20.i2c 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

In ths example: * SPI module is imported * Bus 2 with chip-select 0 is opened * Some data is transfered to slave device

#!/usr/bin/env python

from pyA20.spi 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

Changelog

• pyA20 0.2.12 (8 DEC 2017)

  • Fixed extensions import
  • Update examples

• pyA20 0.2.11 (21 NOV 2017)

  • Fixed mapping on portG
  • Updated README
  • Removed processor checking to allow build scripts
  • Update license

• pyA20 0.2.0 (02 SEP 2014)

  • Updated to enable SPI and I2C control
  • GPIO constant in separate modules
  • Added example files
  • Added support for Python3