Raspberry Pi CPU Temperature Log

If you have any questions or get stuck as you work through this in-class exercise, please ask the instructor for assistance. Enjoy!

Installing The Necessary Software

Open up a terminal shell, this can be done by clicking on its icon (see right)
- Alternatively, a new shell can be opened by pressing crtl+alt+t
Next, ensure that matplotlib is installed by entering the command sudo apt-get install python3-matplotlib
If it installs or confirms that matplotlib is installed, proceed to the next step.

Creating The Python Script

Enter python3 to open the Python interpreter.
Enter these lines of code in order:
```
from gpiozero import CPUTemperature
cpu = CPUTemperature()
print(cpu.temperature)
```
This simply gets the temperature of the CPU and prints it.
Press “ctrl” and “D” on your keyboard to exit the Python interpreter.
Create a new Python file: sudo nano cpu_temp.py

Now let’s make the script more robust by having a log of the temperatures. To do this, enter the following lines:

from gpiozero import CPUTemperature
from time import sleep, strftime, time
from gpiozero import CPUTemperature
cpu = CPUTemperature()
    
with open(“cpu_temp.csv”, “a”) as log:
    while True:
        temp = cpu.temperature
        log.write(‘{0},{1}\n’.format(strftime(‘%Y-%m-%d %H:%M:%S’), str(temp)))

Running this code will keep a log in the form of a CSV file. This file can be found in /home/pi and will be called cpu_temp.csv.
Try running the code and finding the file.
Now that a log is kept, visualization in the form of a realtime graph can be scripted.

Enter this to draw a graph of the temperature:

from gpiozero import CPUTemperature
from time import sleep, strftime, time
import matplotlib.pyplot as plt

cpu = CPUTemperature()
x = []
y = []

def write_temp(temp):
    with open('cpu_temp.csv', 'a') as log:
        log.write('{0},{1}\n'.format(strftime('%Y-%m-%d %H:%M:%S'), str(temp)))

def graph(temp):
    y.append(temp)
    x.append(time())
    plt.clf()
    plt.scatter(x, y)
    plt.plot(x, y)
    plt.draw()

while True:
    temp = cpu.temperature
    write_temp(temp)
    graph(temp)
    plt.pause(1)

Run on Startup

This Python script can be made to run automatically on boot.
Open a new terminal window and enter in crontab -e to open crontab. - If prompted, choose nano from the options given.
Scroll to the bottom of the opened file and enter in this line in a new line: @reboot python3 /home/pi/temp.py
Now, reboot the Raspberry Pi by entering the command: sudo reboot
Once the Raspberry Pi is rebooted and has run for a bit, enter the command: cat cpu_temp.csv
This will display a log of the recent CPU temperature.

NEXT STEP: Electronics and The Raspberry Pi