8-bit DAC on beaglebone with R/2R ladder

import os
import time

#export and enable all pins for DAC output
#Enable Dataline 0 | Pin#: 3 | Header: P8 | GPIO#: 38
os.system("echo 38 > /sys/class/gpio/export")
os.system("echo out > /sys/class/gpio/gpio38/direction")

#Enable Dataline 1 | Pin#: 12 | Header: P8 | GPIO#: 44
os.system("echo 44 > /sys/class/gpio/export")
os.system("echo out > /sys/class/gpio/gpio44/direction")

#Enable Dataline 2 | Pin#: 14 | Header: P8 | GPIO#: 26
os.system("echo 26 > /sys/class/gpio/export")
os.system("echo out > /sys/class/gpio/gpio26/direction")

#Enable Dataline 3 | Pin#: 16 | Header: P8 | GPIO#: 46
os.system("echo 46 > /sys/class/gpio/export")
os.system("echo out > /sys/class/gpio/gpio46/direction")

#Enable Dataline 4 | Pin#: 17 | Header: P8 | GPIO#: 27
os.system("echo 27 > /sys/class/gpio/export")
os.system("echo out > /sys/class/gpio/gpio27/direction")

#Enable Dataline 5 | Pin#: 18 | Header: P8 | GPIO#: 65
os.system("echo 65 > /sys/class/gpio/export")
os.system("echo out > /sys/class/gpio/gpio65/direction")

#Enable Dataline 6 | Pin#: 20 | Header: P8 | GPIO#: 63
os.system("echo 63 > /sys/class/gpio/export")
os.system("echo out > /sys/class/gpio/gpio63/direction")

#Enable Dataline 7 | Pin#: 21 | Header: P8 | GPIO#: 22
os.system("echo 22 > /sys/class/gpio/export")
os.system("echo out > /sys/class/gpio/gpio22/direction")

while(True):

    try:
        #Analog 2
        analog_value = open("/sys/devices/platform/tsc/ain2","rb").read()

        new_value = int(analog_value)
        new_value = 0.062255859*new_value
        new_value = round(new_value)



        #convert dec to binary
        binary_value = bin(new_value)

        #turn on/off 128th bit?
        if binary_value[2] == "1":
            os.system("echo 1 > /sys/class/gpio/gpio22/value")
        elif binary_value[2]  == "0":
            os.system("echo 0 > /sys/class/gpio/gpio22/value")

        print ''
        print binary_value[2]
        print ''

        #turn on/off 64th bit?
        if binary_value[3] == "1":
            os.system("echo 1 > /sys/class/gpio/gpio63/value")
        elif binary_value[3] == "0":
            os.system("echo 0 > /sys/class/gpio/gpio63/value")

        #turn on/off 32nd bit?
        if  binary_value[4] == "1":
            os.system("echo 1 > /sys/class/gpio/gpio65/value")
        elif binary_value[4] == "0":
            os.system("echo 0 > /sys/class/gpio/gpio65/value")

        #turn on/off 16 bit?
        if binary_value[5] == "1":
            os.system("echo 1 > /sys/class/gpio/gpio27/value")
        elif binary_value[5] == "0":
            os.system("echo 0 > /sys/class/gpio/gpio27/value")


        #turn on/off 8th bit?
        if binary_value[6] == "1":
            os.system("echo 1 > /sys/class/gpio/gpio46/value")
        elif binary_value[6] == "0":
            os.system("echo 0 > /sys/class/gpio/gpio46/value")

        #turn on/off 4th bit?
        if binary_value[7] == "1":
            os.system("echo 1 > /sys/class/gpio/gpio26/value")
        elif binary_value[7] == "0":
            os.system("echo 0 > /sys/class/gpio/gpio26/value")


        if binary_value[8] == "1":
            os.system("echo 1 > /sys/class/gpio/gpio44/value")
        elif binary_value[8] == 0:
            os.system("echo 0 > /sys/class/gpio/gpio44/value")


        if binary_value[9] == "1":
            os.system("echo 1 > /sys/class/gpio/gpio38/value")
        if binary_value[9] == "0":
            os.system("echo 0 > /sys/class/gpio/gpio38/value")

        print new_value
        print binary_value
        print "-------"

    except:
        print 0