How to Output a Single Controllable Square Wave Using PWM on the Nvidia Jetson Orin Nano Dev Board

Issue Overview

Users are experiencing difficulties in generating a single controllable square wave using the PWM (Pulse Width Modulation) peripheral on the Nvidia Jetson Orin Nano Dev Board. The primary symptoms include:

• Inability to produce a non-periodic output waveform; once the PWM is enabled, it continuously outputs waveforms.
• Users require specific configurations, such as a duty cycle of 14% and a frequency of 500 kHz, but are unable to stop the PWM signal after one output.

The issue arises during attempts to use PWM for applications like driving LEDs or other peripherals that require precise timing and control. The problem has been reported consistently among users, indicating that it is not isolated to a single instance or setup.

Relevant Specifications

• Hardware: Nvidia Jetson Orin Nano Development Kit
• Software: JetPack version 35.4.1

The impact of this issue significantly affects user experience, especially for those needing precise control over PWM outputs for their projects.

Possible Causes

Several potential causes may contribute to the inability to generate a single controllable square wave:

• Hardware Limitations: The PWM peripheral may have inherent limitations that prevent it from being configured for one-time output.

• Software Bugs: There may be bugs in the JetPack software or libraries that hinder proper PWM functionality.

• Configuration Errors: Incorrect settings in the PWM configuration could lead to continuous output instead of a single pulse.

• Driver Issues: Outdated or incompatible drivers may affect the performance of the PWM peripheral.

• Environmental Factors: Power supply issues or temperature fluctuations might impact hardware performance.

• User Errors: Misunderstanding how to configure PWM settings correctly could lead to unintended behavior.

Troubleshooting Steps, Solutions & Fixes

To address the issue of generating a single controllable square wave, users can follow these troubleshooting steps and solutions:

1. Check Hardware Setup

   • Ensure that you are using the official Nvidia Jetson Orin Nano Development Kit.
   • Verify all connections and components related to the PWM output.

2. Verify Software Version

   • Confirm that you are running JetPack version 35.4.1 or later.
   • Update to the latest version if necessary.

3. Configure PWM Settings

   • Use sysfs to configure the PWM settings:

     echo 0 > /sys/class/pwm/pwm0/enable  # Disable PWM
     echo 20000 > /sys/class/pwm/pwm0/period  # Set period
     echo 2800 > /sys/class/pwm/pwm0/duty_cycle  # Set duty cycle
     echo 1 > /sys/class/pwm/pwm0/enable  # Enable PWM
     

   • Note: Adjust period and duty cycle according to your requirements.

4. Control Output with Delay

   • To achieve precise control over timing, consider implementing a delay function in your code:
     • If using Python, utilize time.sleep() for millisecond delays but note that microsecond-level delays may require additional libraries or custom implementations.

5. Use Alternative Libraries

   • If sysfs does not meet your needs, explore using libraries like jetson-gpio for GPIO control:

     import Jetson.GPIO as GPIO
     
     GPIO.setmode(GPIO.BCM)
     GPIO.setup(pin_number, GPIO.OUT)
     
     # Output a single pulse
     GPIO.output(pin_number, GPIO.HIGH)
     time.sleep(0.0005)  # Adjust time as needed for pulse width
     GPIO.output(pin_number, GPIO.LOW)
     

6. Modify GPIO Pin Registers

   • For advanced users, directly modifying GPIO pin registers through C programming may provide more granular control over PWM outputs.

7. Consult Documentation

   • Refer to Nvidia’s official documentation and community forums for updates on APIs or methods that might facilitate this use case better.

8. Report Bugs

   • If you suspect a bug in the software or libraries, report it on Nvidia’s developer forums or GitHub repositories for further assistance.

Unresolved Aspects

While several workarounds have been discussed, there remains no official API from NVIDIA for outputting a single PWM wave without continuous output. Further investigation into community-developed solutions or updates from NVIDIA may be necessary for a complete resolution.