===== Using PWM from sysfs =====
<WRAP round info 50%>
following Instuction only works for Linux kernel 3.11 or greater 
</WRAP>


==== Where to find PWM devices in sysfs ====

PWM devices are listed under **/sys/class/pwm**

==== export PWM device ====
<WRAP round important 50%>
You must export the PWM at first, otherwise the other commands in this tutorial will not work
</WRAP>
<code>
root@MBaXXX:~ cd /sys/class/pwm                                                   // enter pwm folder in sysfs
root@MBaXXX:/sys/class/pwm cd pwmchip<pwmchipnr>                                  // enter the desired pwmchip folder
root@MBaXXX:/sys/your/path/to/pwmchip/pwmchip<pwmchipnr> echo <pwmnr> > export    // export device PWM<pwmnr> 
root@MBaXXX:/sys/your/path/to/pwmchip/pwmchip<pwmchipnr> cd pwm<pwmnr>            // enter exported pwm device folder 
</code>

++++ example |
<code>
root@MBaXXX:~ cd /sys/class/pwm                                                   
root@MBaXXX:/sys/class/pwm cd pwmchip0 
root@MBaXXX:/sys/class/pwmchip0 echo 0 > export
root@MBaXXX:/sys/class/pwnchip0 cd pwm0
</code>
++++

==== set PWM period ====

<code> 
root@MBaXXX:~ echo <value in nanoseconds> > /sys/class/pwm/pwmchip<pwmchipnr>/pwm<pwmnr>period
</code>

++++ example |
<code>
root@MBaXXX:~ echo 1000000 > /sys/class/pwm/pwmchip0/pwm0/period
</code>
++++

==== set PWM duty cycle ====
<WRAP round important 50%>
The value of duty cycle must be less than the value of pwm period
</WRAP>

<code>
root@MBaXXX:~ echo <value in nanoseconds> > /sys/class/pwm/pwmchip<pwmchipnr>/pwm<pwmnr>duty_cycle
</code>

++++ example |

<code>
root@MBaXXX:~ echo <value in nanoseconds> > /sys/class/pwm/pwmchip0/pwm0/duty_cycle
</code>
++++

==== change polarity of the PWM signal ====

<code>
root@MBaXXX:~ echo "normal" > /sys/class/pwm/pwmchip<pwmchipnr>/pwm<pwmnr>/polarity      // set polarity to normal
root@MBaXXX:~ echo "inversed" > /sys/class/pwm/pwmchip<pwmchipnr>/pwm<pwmnr>/polarity    // set polarity to inversed
</code>

++++ example |
<code>
root@MBaXXX:~ echo "normal" > /sys/class/pwm/pwmchip0/pwm0/polarity 
root@MBaXXX:~ echo "inversed" > /sys/class/pwm/pwmchip0/pwm0/polarity 
</code>
++++
==== enable PWM ====

<code>
root@MBaXXX: echo 1 > /sys/class/pwm/pwmchip<pwmchipnr>/pwm<pwmnr>/enable
</code>

++++ example |

<code>
root@MBaXXX: echo 1 > /sys/class/pwm/pwmchip0/pwm0/enable
</code>
++++

==== disable PWM ====

<code>
root@MBaXXX: echo 0 > /sys/class/pwm/pwmchip<pwmchipnr>/pwm<pwmnr>/enable
</code>

++++ example |

<code>
root@MBaXXX: echo 0 > /sys/class/pwm/pwmchip0/pwm0/enable
</code>
++++