EBC Exercises on BBB - PWM

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PWM

Simply enable the P9_21 to PWM, then connect to the LED. The LED connection could refer to EBC Exercises on BBB - Control LED

SLOTS=/sys/devices/bone_capemgr.*/slots
echo am33xx_pwm > $SLOTS
echo bone_pwm_P9_21 > $SLOTS
cd /sys/devices/ocp.3/pwm_test_P9_21.15/
echo 1000000000 > period
echo  250000000 > duty
echo 1 > run

From now you could see the LED begin to flash. In fact using this pwm we could control servo motor:
http://www.linux.com/learn/tutorials/776799-servo-control-from-the-beaglebone-black/