~~tag>Edge-2L PWM~~

====== Edge-2L PWM ======

===== Introduction =====

This page explains how to use the hardware PWM (Pulse Width Modulation) and guides you through controlling it on the [[products:sbc:edge-2L:applications:gpio:40pin-header|16-Pin Header]].

<WRAP important >
To use the PWM functionality on the Edge-2L, you must attach the Edge-2L IO board.
</WRAP>
===== PWM information =====

|           ^  PWM       ^  PIN  ^  GPIO Name  ^  GPIO Number  ^  DT Overlays Node  ^  Device Node              ^
^  Edge-2L    |  PWM1     |  14   |  GPIO1_B4   |  44          |   edge-2l-io-pwm     |  /sys/class/pwm/pwmchip0  |


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

To use the hardware PWM, you must first enable it by applying a [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]].

Edit the file ''/boot/dtb/rockchip/rk3576-khadas-edge-2l.dtb.overlay.env'' and add the overlay ''edge-2l-io-pwm'' to the ''fdt_overlays'' parameter if it is not already present:

```shell
fdt_overlays=edge-2l-io-pwm
```

Reboot the system for the change to take effect. After rebooting, verify that the PWM device node exists:

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

===== Disable PWM to use as GPIO =====

If you wish to use the pin as a standard GPIO instead of PWM, remove the ''edge-2l-io-pwm'' entry from the ''fdt_overlays'' parameter in the Device Tree Overlay configuration file and reboot.

===== Control PWM via sysfs=====

**Enable and Configure PWM:** 

The following sequence enables PWM channel 0, sets a period of 1,000,000 nanoseconds (1 kHz), a duty cycle of 500,000 nanoseconds (50% duty), and starts the output:
```shell
# Export PWM channel 0
$ echo 0 | sudo tee /sys/class/pwm/pwmchip0/export

# Set period to 1,000,000 ns (1 kHz)
$ echo 1000000 | sudo tee /sys/class/pwm/pwmchip0/pwm0/period

# Set duty cycle to 500,000 ns (50%)
$ echo 500000 | sudo tee /sys/class/pwm/pwmchip0/pwm0/duty_cycle

# Enable PWM output
$ echo 1 | sudo tee /sys/class/pwm/pwmchip0/pwm0/enable
```

Use an oscilloscope to verify the PWM signal on the corresponding pin.

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

<WRAP info > 
When using an oscilloscope to measure the PWM waveform, ensure that the Edge-2L's **GND** is connected to the oscilloscope's ground reference. 
</WRAP>

**Disable PWM:**

To stop the PWM signal:
```shell
echo 0 | sudo tee /sys/class/pwm/pwmchip0/pwm0/enable
```