====== PWM ======

===== Introduction =====

This page introduces the usage of hardware PWM, and leads you to control the hardware PWM on the [[products:sbc:common:applications:gpio:40pin-header|40-Pin Header]].

===== PWM Reference Table =====

|         ^  PWM           ^  PIN  ^  GPIO name      ^  DT overlay node  ^  Device node              ^
^  VIM1   |  ''PWM_AO_A''  |  35   |  ''GPIOAO_3''   |  ''pwm_ao_a''     |  /sys/class/pwm/pwmchip4  |
^  VIM2   |  ''PWM_D''     |  35   |  ''GPIODV_28''  |  ''pwm_d''        |  /sys/class/pwm/pwmchip1  |
^  VIM3   |  ''PWM_F''     |  35   |  ''GPIOH_5''    |  ''pwm_f''        |  /sys/class/pwm/pwmchip4  |
^  VIM3L  |  ''PWM_F''     |  35   |  ''GPIOH_5''    |  ''pwm_f''        | /sys/class/pwm/pwmchip0   |
^  VIM4   |  ''PWM_F''     |  35   |  ''GPIOY_8''    |  ''pwm_f''        |  /sys/class/pwm/pwmchip4  |
^  VIM1S  |  ''PWM_F''     |  35   |  ''GPIOZ_6''    |  ''pwm_f''        |  /sys/class/pwm/pwmchip0  |


===== Enable PWM =====

In order to use the PWM, you need to enable the PWM function via [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]].

<tabbox VIM1/2/3/Edge1>

Edit ''/boot/env.txt'' to add the pwm node to ''overlays'' node if it doesn't exist.

Take VIM3 as an example to enable ''PWM_F'', you need to add ''pwm_f'' node to ''overlays'' node if it doesn't exist.

```shell
overlays=uart3 pwm_f i2c3 i2s os08a10 watchdog
```

After reboot, you will see the pwm device node.

```shell
$ ls /sys/class/pwm/pwmchip4
device  export  npwm  power  subsystem  uevent  unexport
```

<tabbox VIM3L>

Edit ''/boot/env.txt'' to add the pwm node to ''overlays'' node if it doesn't exist.

Take VIM3L as an example to enable ''PWM_F'', you need to add ''pwm_f'' node to ''overlays'' node if it doesn't exist.

```shell
overlays=uart3 pwm_f i2c3 i2s watchdog
```

After reboot, you will see the pwm device node.

```shell
$ ls /sys/class/pwm/pwmchip0
device  export  npwm  power  subsystem  uevent  unexport
```


<tabbox VIM3 with 5.15 kernel>

Edit ''/boot/dtb/amlogic/kvim3.dtb.overlay.env'' to add pwm node to ''fdt_overlays'' node if it doesn't exist.


You need to add ''pwm_f'' to node ''fdt_overlays'' if it doesn't exist to enable ''PWM_F''.

```shell
fdt_overlays=pwm_f

```

After reboot, you will see the pwm device node.

<tabbox VIM3L with 5.15 kernel>

Edit ''/boot/dtb/amlogic/kvim3l.dtb.overlay.env'' to add pwm node to ''fdt_overlays'' node if it doesn't exist.


You need to add ''pwm_f'' to node ''fdt_overlays'' if it doesn't exist to enable ''PWM_F''.

```shell
fdt_overlays=pwm_f

```

After reboot, you will see the pwm device node.

<tabbox VIM4>

Edit ''/boot/dtb/amlogic/kvim4.dtb.overlay.env'' to add pwm node to ''fdt_overlays'' node if it doesn't exist.


You need to add ''pwm_f'' to node ''fdt_overlays'' if it doesn't exist to enable ''PWM_F''.

```shell
fdt_overlays=pwm_f

```

After reboot, you will see the pwm device node.

```shell
$ ls /sys/class/pwm/pwmchip4
device  export  npwm  power  subsystem  uevent  unexport
```

<tabbox VIM1S>

Edit ''/boot/dtb/amlogic/kvim1s.dtb.overlay.env'' to add pwm node to ''fdt_overlays'' node if it doesn't exist.


You need to add ''pwm_f'' to node ''fdt_overlays'' if it doesn't exist to enable ''PWM_F''.

```shell
fdt_overlays=pwm_f

```

After reboot, you will see the pwm device node.

```shell
$ ls /sys/class/pwm/pwmchip0
device  export  npwm  power  subsystem  uevent  unexport
```
</tabbox>


===== Control PWM =====

**Enable PWM:**

<tabbox VIM1/3/4> 

```shell
echo 1 | sudo tee /sys/class/pwm/pwmchip4/export
echo 1000000 | sudo tee /sys/class/pwm/pwmchip4/pwm1/period
echo 500000 | sudo tee /sys/class/pwm/pwmchip4/pwm1/duty_cycle
echo 1 | sudo tee /sys/class/pwm/pwmchip4/pwm1/enable
```

<tabbox VIM2> 

```shell
echo 1 | sudo tee /sys/class/pwm/pwmchip1/export
echo 1000000 | sudo tee /sys/class/pwm/pwmchip1/pwm1/period
echo 500000 | sudo tee /sys/class/pwm/pwmchip1/pwm1/duty_cycle
echo 1 | sudo tee /sys/class/pwm/pwmchip1/pwm1/enable
```

<tabbox VIM3L/1S> 

```shell
echo 1 | sudo tee /sys/class/pwm/pwmchip0/export
echo 1000000 | sudo tee /sys/class/pwm/pwmchip0/pwm1/period
echo 500000 | sudo tee /sys/class/pwm/pwmchip0/pwm1/duty_cycle
echo 1 | sudo tee /sys/class/pwm/pwmchip0/pwm1/enable
```

<tabbox VIM4/4N with 5.15 kernel> 

```shell
echo 1 | sudo tee /sys/class/pwm/pwmchip12/export
echo 1000000 | sudo tee /sys/class/pwm/pwmchip12/pwm1/period
echo 500000 | sudo tee /sys/class/pwm/pwmchip12/pwm1/duty_cycle
echo 1 | sudo tee /sys/class/pwm/pwmchip0/pwm12/enable
```

</tabbox>

Use an oscilloscope to check if the pins have been successfully enabled.

{{products:sbc:common:applications:gpio:pwm-oscilloscope.png|pwm-oscilloscope}}

<WRAP info >
If you use an oscilloscope to view the PWM waveform, remember that the SBC and the oscilloscope need to share the same GND (ground).
</WRAP>

**Disable PWM:**

<tabbox VIM1/3/4> 
```shell
echo 0 | sudo tee /sys/class/pwm/pwmchip4/pwm1/enable
```
<tabbox VIM2> 
```shell
echo 0 | sudo tee /sys/class/pwm/pwmchip1/pwm1/enable
```
<tabbox VIM3L/1S> 
```shell
echo 0 | sudo tee /sys/class/pwm/pwmchip0/pwm1/enable
```

<tabbox VIM4/4N with 5.15 kernel> 
```shell
echo 0 | sudo tee /sys/class/pwm/pwmchip12/pwm1/enable
```

</tabbox>

===== Disable PWM to Use GPIO =====

If you want to use normal GPIO instead of PWM, you can remove the PWM node in [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]].