User manual

import RPi.GPIO as GPIO

import time

import os

g1 = 1; g2 = 10; g3 = 100; g4 = 500

GPIO.setmode(GPIO.BCM)

LED = [4,18,23]

for i in range(3):

GPIO.setup(LED[i], GPIO.OUT, initial=False)

print (“Ctrl+C exits the programme")

try:

while True:

s = os.statvfs('/')

f = s.f_bsize * s.f_bavail / 1000000

if f < g1:

x = "100"

elif f < g2:

x = "110"

elif f < g3:

x = "010"

elif f < g4:

x = "011"

else:

x = "001"

for i in range(3):

GPIO.output(LED[i], int(x[i]))

time.sleep(1.0)

except KeyboardInterrupt:

GPIO.cleanup()

When you run the programme the three LEDs will constantly show the free space on the memory card. Try it

out by copying large files over the network to the memory card and delete them. The indicator updates

automatically.

7.1.1 How does it work?

The programme uses the Python module os to calculate the free space, which provides the basic functions of

the operating system.

import os The module os as any other module needs to be imported at the beginning of the programme.

g1 = 1; g2 = 10; g3 = 100; g4 = 500 Those command lines define the limits of the free space areas, where

the indication is supposed to switch. The programme uses megabytes and not bytes, as such figures are

better comprehensible, to keep it simple, so to say. You can modify the limits at any time; however, the four

values must be arranged in ascending order according to size.