I was trying to listen an FM program according to the instructions on http://wiki.analog.com/resources/tools-software/fm-radio.
But I couldn't finish the following operation. The system reponded with " Permission denied" although I got the priority of root.
echo fast_attack > /sys/bus/iio/devices/iio:device1/in_voltage1_gain_control_mode
Consequently, I heard something like "peng peng " from the phone output of Zedboard after I used iio_fm_radio 89.9 which is one FM broadcast frequency in Shanghai?