Circumventing Censorship with a Tor Bridge - BeagleBone for Secret Agents - page 55

Controlling the hardware with pyBBIO
We installed the Stem library when we installed Tor; so, now we need to install the Ada-
fruit BBIO library by performing the following commands:
sudo apt-get install build-essential python-dev
python-setuptools python-pip python-smbus -y
sudo pip install Adafruit_BBIO
sudo pip install pyserial
The Adafruit library conveniently enables the device tree overlays, which are the files
that describe the hardware configuration of BBB to the kernel, at runtime. Therefore, there
is no need to manipulate the configuration via the sysfs as everything is handled in the
Python library. The code models each hardware component as its own Python class. The
LED modeled by the TorFreedomLED class is the most straightforward. We need the
LED to blink; this is accomplished by toggling the output high, sleeping the executing
thread briefly, and then toggling the output low to turn it off. To set up the GPIO, we only
need to call GPIO.setup , by passing in the pin and the direction:
import Adafruit_BBIO.GPIO as GPIO
class TorFreedomLED(object):
def __init__(self):
self.pin = 'P9_15'
GPIO.setup(self.pin, GPIO.OUT)
def on(self):
GPIO.output(self.pin, GPIO.HIGH)
def off(self):
GPIO.output(self.pin, GPIO.LOW)
def blink(self):
self.on()
sleep(.5)
self.off()
The LCD, controlled by the FrontPanelDisplay class, writes to the serial port,
/dev/ttyO4 , on BBB's UART 4 at 9600 baud. The LCD only receives information;