User manual

For the programme to be universal and easily alterable, we will ow define three variables:

z Number of LEDs

The number of LEDs is automatically adopted from the list

LED by using the

function

len().

w Repetitions

Each pattern is repeated five times by default so that the pattern is better for

better recognize it better detected. This number can be changed as desired, and

is then applies to all patterns.

t Time

This variable indicates how long a flashing LED is turned on. The pause, that

follows will last just as long. The name

t is commonly used in all programming

languages for variables that store time intervals in programs.

The values defined as variables are introduced only here at this point within the program and can be easily

changed. Following these definitions the actual program begins.

print (“Light effects selection"); print ("1 – cyclical chaser")

print ("2 – chase bidirectional"); print ("3 – ascending and descending")

print ("4 – all flashing simultaneously"); print ("5 – all flashing at random")

print (“Ctrl+C exits the program")

These lines will provide the user with an on-screen guidance on which numeric key will display which

pattern.

Fig. 5.3: The program on-screen.

After the selection has been indicated, the main loop of the program will start. We are also using here the

infinite loop

while True:, whicmeh is embedded in the statement try...except.

e = raw_input (“Please select a pattern: ") Right at the start of the loop, the program waits for the

user’s input which then is stored in the variable

e. The function raw_input() adopts the input as plain text,

without evaluating. In contrast,

input(), which are mathematical operations or variable names, are

evaluated on spot. That means that

raw_input() is in most cases therefore the better choice, because you

don’t have to worry about the many events of possible inputs.