Skip to main content

Auto-Run Python Code on Boot

In the previous sections, we learned many Python embedded programming cases. Some of you may wonder: can we place our already-written Python code on the WalnutPi and have it automatically execute on boot? The answer is yes, and it's a very practical feature. This section will explain it in detail.

Method for Desktop Systems​

First, let's write a piece of test Python code that uses the onboard LED blinking effect as a demonstration, along with a "Hello WalnutPi!" print message. The code is as follows (available in the WalnutPi development board resource package → Example Programs → Other Usage Tips):

'''
Experiment Name: LED Blinking
Experiment Platform: WalnutPi
'''

# Import related modules
import board,time
from digitalio import DigitalInOut, Direction

# Construct and initialize LED object
led = DigitalInOut(board.LED) # Define pin number
led.direction = Direction.OUTPUT  # IO as output

while True:

    led.value = 1 # Output HIGH, turn on onboard blue LED

    time.sleep(0.5)

    led.value = 0 # Output LOW, turn off onboard blue LED

    time.sleep(0.5)

    print("Hello WalnutPi!") # Output print message

Save the above code as led_blink.py and place it in the WalnutPi's /home/pi directory for testing. You can transfer it using Thonny or copy it directly to the directory using a USB drive.

auto_run1

Then, on the WalnutPi desktop, click Start Menu → Settings → Session and Startup.

auto_run2

After it opens, click Application Autostart, then click + Add at the bottom left. In the popup dialog, configure the following:

  • Name: Define the application name. We'll use START here; you can change it as desired.
  • Description: A description of this application; can be left blank.
  • Command: Use the following Python terminal command to start the .py script. Be sure to use Python3 (note capitalization), because this program has elevated privileges on the WalnutPi, giving it admin permissions to run Python scripts and avoiding permission issues.
Python3 /home/pi/led_blink.py
  • Trigger: Select "on login".

auto_run3

After confirming, you can see the START program appear in the list.

auto_run4

After creation, you'll notice a startup file in the /home/pi/.config/autostart directory. Right-click and select "Edit Launcher" for more editing options.

auto_run5

As shown below, you can check the Run in terminal option so that opening this application will pop up a new terminal on the desktop for viewing debug information. If unchecked, it runs in the background.

auto_run6

After saving, you can double-click the application to test it. You'll see a new terminal pop up on the desktop, printing the output from led_blink.py.

auto_run7

The onboard LED blinks periodically!

auto_run8

Execute the reboot command and you'll see the WalnutPi board pop up a terminal printing "Hello WalnutPi!" and the LED blinking, indicating the Python code auto-runs successfully on boot.

sudo reboot

Method for Headless (No Desktop) Systems​

The previous section covered the method for WalnutPi desktop systems. Here's the method for headless systems, using a boot startup service. This method also works for desktop systems!

As before, first write a piece of test Python code using the onboard LED blinking effect as a demonstration, along with a "Hello WalnutPi!" print message. The code is as follows (available in the WalnutPi development board resource package → Example Programs → Other Usage Tips):

'''
Experiment Name: LED Blinking
Experiment Platform: WalnutPi
'''

# Import related modules
import board,time
from digitalio import DigitalInOut, Direction

# Construct and initialize LED object
led = DigitalInOut(board.LED) # Define pin number
led.direction = Direction.OUTPUT  # IO as output

while True:

    led.value = 1 # Output HIGH, turn on onboard blue LED

    time.sleep(0.5)

    led.value = 0 # Output LOW, turn off onboard blue LED

    time.sleep(0.5)

    print("Hello WalnutPi!") # Output print message

Save the above code as led_blink.py and place it in the WalnutPi's /home/pi directory for testing. You can transfer it using Thonny or copy it directly using a USB drive.

auto_run1

Create a new start.service file in the /lib/systemd/system directory. (This file is available in the WalnutPi development board resource package → Example Programs → Other Usage Tips → Headless System Method directory.)

sudo nano /lib/systemd/system/start.service

Modify the content as follows:

[Unit]
Description=Expand partition size

[Service]
Type=oneshot
ExecStart=Python3 /home/pi/led_blink.py
RemainAfterExit=yes
StandardOutput=null

[Install]
WantedBy=multi-user.target

After saving, give the file full permissions:

sudo chmod 777 /lib/systemd/system/start.service

auto_run10

Enable the service:

 sudo systemctl enable start.service

auto_run11

Execute the reboot command. You'll see the LED blinking after the WalnutPi restarts, indicating the Python code auto-runs successfully. Since this method runs in the background, you won't see the "Hello WalnutPi!" print message!

sudo reboot

auto_run8


Note

Both methods above work by launching the Python script via a command. Users can modify the command to run specific Linux commands or software on boot as needed.