PERIPLEX PWM

This section explains how to interact with the PWM's chip generated on Vaaman via Periplex.

How to Generate PWM’s on the Vaaman ?

Create the json file:

To generate 5-PWM's chip, Your need to create a json file and copy the following content into it.

Tip

how to create the json configuration file for periplex, You can check this Usage Guide

{
   "uart": [],
   "i2c": [],
   "gpio": [],
   "pwm": [
      {
         "id": 0,
         "PWM": "GPIOT_RXP28"
      },
      {
         "id": 1,
         "PWM": "GPIOL_73"
      },
      {
         "id": 2,
         "PWM": "GPIOR_173"
      },
      {
         "id": 3,
         "PWM": "GPIOR_174"
      },
      {
         "id": 4,
         "PWM": "GPIOT_RXN27"
      }
   ],
   "ws": [],
   "spi": [],
   "onewire": [],
   "can": [],
   "i2s": []
}

Run the periplex-sync command:
- For example, if the JSON configuration for 5-PWM's chip is stored into the device.json file, the periplex-sync command would look like this:
```
sudo periplex-sync -p device.json
```
- After successfully running of periplex-sync command, it will ask for the reboot.
Reboot the board:
- After rebooting, all configurations have been successfully applied.
- You will get the 5-PWM's chip generated through Periplex like this:
```
   vicharak@vicharak:/sys/class/pwm$ ls
   pwmchip0  pwmchip1  pwmchip2  pwmchip3  pwmchip4  pwmchip5
```

How to interact with the generated PWM’s ?

The Periplex platform dynamically exposes PWM controllers as pwmchip devices, which can be accessed via paths like:

/sys/class/pwm/pwmchip1
/sys/class/pwm/pwmchip2
/sys/class/pwm/pwmchip3
...

Configuring and Controlling PWM’s chip

Each PWM chip manages a PWM channel. For example, you want control pwmchip1.

Export a PWM channel:

For export a PWM channel of pwmchip1:

# Export the PWM channel
echo 0 > /sys/class/pwm/pwmchip1/export

Enable a PWM channel and set duty_cycle and period:
- For enable and set the duty_cycle and period of pwmchip1:
```
# Set the period (in nanoseconds)
echo 2000000 > /sys/class/pwm/pwmchip1/pwm0/period

# Set the duty cycle (in nanoseconds)
echo 1500000 > /sys/class/pwm/pwmchip1/pwm0/duty_cycle

# Enable the PWM signal
echo 1 > /sys/class/pwm/pwmchip1/pwm0/enable
```
- Period defines the total time for one cycle of the PWM signal.
- Duty_cycle cycle specifies how long the signal stays high during one period.
- Enable starts the PWM output.

Disable a PWM channel:

To stop the PWM output:

echo 0 > /sys/class/pwm/pwmchip1/pwm0/enable

Unexport the PWM channel:
- When you’re done using the PWM channel, it’s a good practice to unexport it:
```
echo 0 > /sys/class/pwm/pwmchip1/unexport
```

Note

The duty cycle value must always be less than or equal to the period to ensure proper PWM operation.
Ensure you have the correct permissions to access PWMs. You may need to run these commands with sudo.

Example of using the PWM protocol

This example demonstrates controlling a 3200 RPM DC motor using the PWM (Pulse Width Modulation) protocol.

Setting a higher duty cycle increases the motor’s speed.
Setting a lower duty cycle decreases the motor’s speed.

The motor’s rotation speed depends on the duty cycle — running faster with a higher value and slower with a lower value.

Export a PWM Channel: Prepares the PWM channel for motor control.
Enable and Configure PWM: Sets the period (cycle duration) and duty cycle (signal high time) to control motor speed, then starts the motor.
Disable PWM: Stops the motor by halting the output signal.
Unexport PWM Channel: Releases the PWM channel, resetting it for future use.

PERIPLEX GPIO

PERIPLEX WS