manual ppp0
iface ppp0 inet ppp
    pre-up echo 61 > /sys/class/gpio/export
    pre-up echo out > /sys/class/gpio/gpio61/direction
    pre-up echo 0 > /sys/class/gpio/gpio61/value
    pre-up sleep 7
    post-down echo 1 > /sys/class/gpio/gpio61/value
    post-down echo 61 > /sys/class/gpio/unexport