Freenove Ultimate Starter Kit, Manual

Page: 186 / 286

Chapter 17 74HC595 & LEDBar Graph
186
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MSBFIRST = 2
#define the pins connect to 74HC595
dataPin = 11 #DS Pin of 74HC595(Pin14)
latchPin = 13 #ST_CP Pin of 74HC595(Pin12)
clockPin = 15 #SH_CP Pin of 74HC595(Pin11)
d e f setup ( ):
GPIO . setmode ( GPIO . BOARD ) # Number GPIOs by its physical location
GPIO . setup ( dataPin , GPIO . OUT )
GPIO . setup ( latchPin , GPIO . OUT )
GPIO . setup ( clockPin , GPIO . OUT )
# shiftOut function, use bit serial transmission.
d e f shiftOut ( dPin , cPin , order , val ):
f o r i i n range ( 0 , 8 ):
GPIO . output ( cPin , GPIO . LOW );
i f ( order = = LSBFIRST ):
GPIO . output ( dPin ,( 0x01 &( val >> i )== 0x01 ) a n d GPIO . HIGH o r GPIO . LOW )
e l if ( order = = MSBFIRST ):
GPIO . output ( dPin ,( 0x80 &( val << i )== 0x80 ) a n d GPIO . HIGH o r GPIO . LOW )
GPIO . output ( cPin , GPIO . HIGH );
d e f loop ( ):
w h ile T r ue :
x = 0x01
f o r i i n range ( 0 , 8 ):
GPIO . output ( latchPin , GPIO . LOW ) #Output low level to latchPin
shiftOut ( dataPin , clockPin , LSBFIRST , x ) #Send serial data to 74HC595
GPIO . output ( latchPin , GPIO . HIGH ) #Output high level to latchPin, and 74HC595
will update the data to the parallel output port.
x < < = 1 # make the variable move one bit to left once, then the bright LED move
one step to the left once.
time . sleep ( 0.1 )
x = 0x80
f o r i i n range ( 0 , 8 ):
GPIO . output ( latchPin , GPIO . LOW )
shiftOut ( dataPin , clockPin , LSBFIRST , x )
GPIO . output ( latchPin , GPIO . HIGH )
x > > = 1
time . sleep ( 0.1 )
d e f destroy (): # When 'Ctrl+C' is pressed, the function is executed.
GPIO . cleanup ()
i f __name__ = = '__main__' : # Program starting from here