More Verbose

10_74HC595_LED.py

@@ -2,6 +2,7 @@
 #================================================
 #
 #	This program is for SunFounder SuperKit for Rpi.
+#	or for the Velleman VMS-502
 #
 #	Extend use of 8 LED with 74HC595.
 #
@@ -10,12 +11,18 @@
 #
 #=================================================
 
-import RPi.GPIO as GPIO
+import RPi.GPIO as GPIO		#if you use a standard Raspberry PI
+#import RTk.GPIO as GPIO	#if you use a RTk.GPIO USB Board for PC or Mac
+#import ASUS.GPIO as GPIO	#if you use a ASUS TinkerBoard
 import time
+import sys			#for displaying without newline
 
-SDI   = 11
-RCLK  = 12
-SRCLK = 13
+#Datasheet: http://www.ti.com/lit/ds/symlink/sn74hc595.pdf
+
+#name = GPIO Pin
+SDI   = 11	#75hc595 PIN 14: Serial Data IN
+RCLK  = 12	#74hc595 PIN 12: storage Register CLocK
+SRCLK = 13	#74hc595 PIN 11: Shift Register CLocK
 
 #===============   LED Mode Defne ================
 #	You can define yourself, in binay, and convert it to Hex 
@@ -33,41 +40,62 @@ def print_msg():
 	print 'Program is running...'
 	print 'Please press Ctrl+C to end the program...'
 
+
 def setup():
-	GPIO.setmode(GPIO.BOARD)    # Number GPIOs by its physical location
-	GPIO.setup(SDI, GPIO.OUT)
-	GPIO.setup(RCLK, GPIO.OUT)
-	GPIO.setup(SRCLK, GPIO.OUT)
-	GPIO.output(SDI, GPIO.LOW)
-	GPIO.output(RCLK, GPIO.LOW)
-	GPIO.output(SRCLK, GPIO.LOW)
+	GPIO.setmode(GPIO.BOARD)	# Number GPIOs by its physical location
+	GPIO.setup(SDI, GPIO.OUT)	# Define Pin as OUTPUT
+	GPIO.setup(RCLK, GPIO.OUT)	# Define Pin as OUTPUT
+	GPIO.setup(SRCLK, GPIO.OUT)	# Define Pin as OUTPUT
+	GPIO.output(SDI, GPIO.LOW)	# Set Pin to 0
+	GPIO.output(RCLK, GPIO.LOW)	# Set Pin to 0
+	GPIO.output(SRCLK, GPIO.LOW)	# Set Pin to 0
+
+
+#write as Serial Bits to HC595 by waking bitwise through the byte
 
 def hc595_in(dat):
-	for bit in range(0, 8):	
-		GPIO.output(SDI, 0x80 & (dat << bit))
+	sys.stdout.write( "\r" + '{:08b}'.format(dat) )	# display on screen
+	sys.stdout.flush()				#
+	sys.stdout.write( "\n" )			#
+	sys.stdout.flush()				#
+	for bit in range(0, 8):
+		GPIO.output(SDI, 0x80 & (dat << bit))	#<< is the bitwise shift operator
 		GPIO.output(SRCLK, GPIO.HIGH)
-		time.sleep(0.001)
+		time.sleep(0.1)
+		sys.stdout.write( "x" )			#
+		sys.stdout.flush()			# display on screen
 		GPIO.output(SRCLK, GPIO.LOW)
 
-def hc595_out():
+
+#send an impulse to RCLK that will load the data from the Shift Register in the Chip to the Display Register in the Chip
+
+def hc595_out():	#pin 12: storage Register CLocK
 	GPIO.output(RCLK, GPIO.HIGH)
 	time.sleep(0.001)
 	GPIO.output(RCLK, GPIO.LOW)
+	sys.stdout.write( " (X) Loading to DisplayRegister ")
+	sys.stdout.flush()
+
 
 def loop():
 	WhichLeds = LED0	# Change Mode, modes from LED0 to LED3
-	sleeptime = 0.1		# Change speed, lower value, faster speed
+	sleeptime = 1		# Change speed, lower value, faster speed
 	while True:
+		#walk from bit 1 to bit 8
 		for i in range(0, len(WhichLeds)):
+			#write data serial to 74hc595
 			hc595_in(WhichLeds[i])
+			#adopt the data in the shift register
 			hc595_out()
 			time.sleep(sleeptime)
 
+		#reverse direction
 		for i in range(len(WhichLeds)-1, -1, -1):
 			hc595_in(WhichLeds[i])
 			hc595_out()
 			time.sleep(sleeptime)
 
+
 def destroy():   # When program ending, the function is executed. 
 	GPIO.cleanup()