Additional GPIO Pins for Tachometer on Jetson Orin Nano

Issue Overview

Users of the Nvidia Jetson Orin Nano Development Board are seeking information about the availability of additional GPIO pins for tachometer functionality. The specific context involves:

• The known existence of pin #208 (GPIO8) for tachometer use
• The need to sense multiple fans in a system
• Uncertainty about whether other pins can be used for tachometer functions
• Questions about the flexibility of GPIO pin assignments for this purpose

This issue is relevant for users who require expanded fan monitoring capabilities beyond what is provided by the default tachometer pin, potentially impacting system cooling management and performance monitoring in multi-fan setups.

Possible Causes

The need for additional tachometer pins can arise from several factors:

1. System Complexity: More advanced or larger systems may incorporate multiple fans, necessitating additional tachometer inputs.
2. Cooling Requirements: High-performance applications might require precise monitoring of multiple cooling components.
3. Custom Enclosures: Users developing custom enclosures or cooling solutions may need to monitor fans in various locations.
4. Redundancy: Some setups might benefit from redundant fan speed monitoring for critical systems.
5. Expansion: Users might be expanding their existing setup and require additional monitoring capabilities.

Troubleshooting Steps, Solutions & Fixes

To address the need for additional tachometer functionality on the Jetson Orin Nano, follow these steps and considerations:

1. Confirm GPIO Flexibility:

   • As confirmed in the forum, any GPIO pin can be used for tachometer functionality, similar to GPIO8.

2. Identify Available GPIO Pins:

   • Consult the Jetson Orin Nano technical specifications or pinout diagram to identify unused GPIO pins.
   • Ensure the selected pins are not reserved for other critical functions.

3. Configure Additional GPIO Pins:

   • Use the Jetson GPIO Python library or direct register manipulation to configure the chosen GPIO pins for input mode.

   • Example Python code to set up a GPIO pin (replace X with the desired pin number):

     import Jetson.GPIO as GPIO
     
     GPIO.setmode(GPIO.BOARD)
     GPIO.setup(X, GPIO.IN)
     

4. Implement Tachometer Reading:

   • Develop software to read the pulse frequency from the newly configured GPIO pins.

   • Use interrupts or polling methods to capture fan speed data.

   • Example interrupt-based approach:

     import Jetson.GPIO as GPIO
     import time
     
     def tachometer_callback(channel):
         global pulse_count
         pulse_count += 1
     
     GPIO.setmode(GPIO.BOARD)
     GPIO.setup(X, GPIO.IN)
     GPIO.add_event_detect(X, GPIO.RISING, callback=tachometer_callback)
     
     pulse_count = 0
     start_time = time.time()
     
     try:
         while True:
             time.sleep(1)
             elapsed_time = time.time() - start_time
             rpm = (pulse_count / elapsed_time) * 60 / 2  # Assuming 2 pulses per revolution
             print(f"Fan RPM: {rpm}")
             pulse_count = 0
             start_time = time.time()
     except KeyboardInterrupt:
         GPIO.cleanup()
     

5. Update System Configuration:

   • Modify any relevant system configuration files to recognize the new tachometer inputs.
   • Update cooling management software to incorporate data from additional fans.

6. Testing and Calibration:

   • Verify the accuracy of readings from the new tachometer inputs.
   • Calibrate the system if necessary to ensure consistent measurements across all monitored fans.

7. Documentation:

   • Document the pin assignments and any custom software implementations for future reference and maintenance.

8. Consider Hardware Limitations:

   • Be aware of any potential limitations in the number of simultaneous GPIO interrupts or polling frequency that the Jetson Orin Nano can handle.
   • If monitoring a large number of fans, consider using a dedicated fan controller or multiplexer to aggregate signals.

By following these steps, users can effectively expand the tachometer capabilities of their Jetson Orin Nano to monitor multiple fans, enhancing their system’s cooling management and performance monitoring capabilities.