Spency's digital-diy 16F PIC micro Tutorial

16F RGB LED Example

RGB LED's are a true amazement to watch. I don't have access to any RGB LED controllers, so I developed my own little program that will randomly cycle the intensity of each primary color.

RGB color is additive, that is, equal intensities of Red + Green + Blue will produce white (not black). Here's an example of additive color;

Having no experience with RGB LED's, I was really in the deep end, and most of the forums online suggested using MAX6696 LED controllers and such, but I cant get hold of them.

The LED's can be controlled by PWM, Pulse Wave Modulation, and a PIC micro has the capability to drive a single RGB LED without a driver, you could control more than one, but you would have to be sure that the PIC does not draw too much current. I used the ULN2003 to drive several in parallel, as the ULN2003 can handle up to 500mA continuous.

Unfortunately, ISIS does not provide a simulation for RGB LED's, so a brief explanation will have to do. For this example, one RGB LED will be driven by a PIC micro.

The program will make the RGB LED Cycle through every primary color randomly, and it will make sure that the chosen color can cycle in the direction that was chosen randomly (i.e. wont 're-cycle' red down of red is already at minimum).

Dim R_Delay as Word
Dim G_Delay as Word
Dim B_Delay as Word

Dim Temp as Word

Dim R_Loops as Word
Dim G_Loops as Word
Dim B_Loops as Word

Dim R_Max As Word
Dim G_Max As Word
Dim B_Max As Word

Dim TimeScale as Word
Dim Max_Time as Word

Dim Last as Word
Dim Percent as Word

DIM RND1 as Word
Dim RND2 as Word

Dim DTemp as Dword

Symbol B = PORTA.1
Symbol G = PORTA.2
Symbol R = PORTA.3

DEVICE = 16F877A
XTAL = 4
;--------------------------------------------------------

;--------------------------------------------------------

CONFIG XT_OSC , WDT_OFF , PWRTE_ON , BODEN_OFF , LVP_OFF , CPD_OFF, CP_OFF , DEBUG_OFF

ALL_DIGITAL = TRUE

SEED $0345

TRISB = %11111111
	
TRISA = %00000000
PORTA = $FF

R_Max = 250		' Adjust so that the proper color spectrum is shown 
G_Max = 102		' 
B_Max = 100		'  
						
TimeScale = 3500	' Controls the rate in which the colors change 
		  	'   (Note: Max Brightness control will modify time!)

R_Loops = TimeScale / R_Max 	   ' The timescale provides the number of loops 
G_Loops = TimeScale / G_Max	   '  for each display of a new color and to
B_Loops = TimeScale / B_Max	   '  ensure best performance, each individual color
		                   '  loop is modified to fit into the timescale selected
R_Delay = R_Max		' Set values to known amounts			   
G_Delay = G_Max
B_Delay = B_Max

If R_Max > G_Max and R_Max > B_Max Then Max_Time = R_Max	   ' Also ensures maximum 
If G_Max > R_Max and G_Max > B_Max Then Max_Time = G_Max	   '  refresh rate depending
If B_Max > R_Max and B_Max > G_Max Then Max_Time = B_Max	   '  on user settings

Main:

   RND1 = Random 	 	   	 	   ' Produce a random number
   
   Select RND1				    ' Depending on the value produced 
   		  Case 0 To 10000	   '  will control the color flow
		  	   Goto Red_Up
		  Case 9999 To 20000
		  	   Goto Red_Down
		  Case 19999 To 30000
		  	   Goto Green_Up
		  Case 29999 To 40000
		  	   Goto Green_Down
		  Case 39999 To 50000
		  	   Goto Blue_Up
		  Case 49999 To 60000
		  	   Goto Blue_Down	
	EndSelect
	
	Goto Main		 ' If the value was >60000 then get a new one 
	
Red_Up:	 				 ' Increase the amount of red

   If R_Delay = R_Max Then Goto Main
   
   For R_Delay = 0 To R_Max
   
   	   For Temp = 0 To R_Loops
   	   	   R = 1
	   	   Delayus R_Delay
	   	   R = 0
	   	   Delayus Max_Time - R_Delay
   	   	   G = 1
	   	   Delayus G_Delay
	   	   G = 0
	   	   Delayus Max_Time - G_Delay
   	   	   B = 1
	   	   Delayus B_Delay
	   	   B = 0
	   	   Delayus Max_Time - B_Delay
   	   Next   

   Next
   
   R_Delay = R_Max
   
   Goto Main   
      
Red_Down:			' Decrease the amount of red
   If R_Delay = 0 Then Goto Main	
      
   For R_Delay = R_Max To 0 Step -1
   
   	   For Temp = 0 To R_Loops
   	   	   R = 1
	   	   Delayus R_Delay
	   	   R = 0
	   	   Delayus Max_Time - R_Delay
   	   	   G = 1
	   	   Delayus G_Delay
	   	   G = 0
	   	   Delayus Max_Time - G_Delay
   	   	   B = 1
	   	   Delayus B_Delay
	   	   B = 0
	   	   Delayus Max_Time - B_Delay
   	   Next   

   Next
   
   R_Delay = 0
   
   Goto Main 
   
      
Green_Up:	  	   	' Increase the amount of green

   If G_Delay = G_Max Then Goto Main

   For G_Delay = 0 To G_Max
   
   	   For Temp = 0 To G_Loops
   	   	   R = 1
	   	   Delayus R_Delay
	   	   R = 0
	   	   Delayus Max_Time - R_Delay
   	   	   G = 1
	   	   Delayus G_Delay
	   	   G = 0
	   	   Delayus Max_Time - G_Delay
   	   	   B = 1
	   	   Delayus B_Delay
	   	   B = 0
	   	   Delayus Max_Time - B_Delay
   	   Next   

   Next
   
   G_Delay = G_Max
   
   Goto Main
   
      
Green_Down:	 	   		' Decrease the amount of green
   
   If G_Delay = 0 Then Goto Main  
      
   For G_Delay = G_Max To 0 Step -1
   
   	   For Temp = 0 To G_Loops
   	   	   R = 1
	   	   Delayus R_Delay
	   	   R = 0
	   	   Delayus Max_Time - R_Delay
   	   	   G = 1
	   	   Delayus G_Delay
	   	   G = 0
	   	   Delayus Max_Time - G_Delay
   	   	   B = 1
	   	   Delayus B_Delay
	   	   B = 0
	   	   Delayus Max_Time - B_Delay
   	   Next   

   Next
   
   G_Delay = 0
   
   Goto Main
   
      
Blue_Up:	  	   	' Increase the amount of blue

   If B_Delay = B_Max Then Goto Main

   For B_Delay = 0 To B_Max
   
   	   For Temp = 0 To B_Loops
   	   	   R = 1
	   	   Delayus R_Delay
	   	   R = 0
	   	   Delayus Max_Time - R_Delay
   	   	   G = 1
	   	   Delayus G_Delay
	   	   G = 0
	   	   Delayus Max_Time - G_Delay
   	   	   B = 1
	   	   Delayus B_Delay
	   	   B = 0
	   	   Delayus Max_Time - B_Delay
   	   Next   

   Next
   
   B_Delay = B_Max
   
   Goto Main
   
      
Blue_Down:	 	   	    ' Decrease the amount of blue

   If B_Delay = 0 Then Goto Main
   
   For B_Delay = B_Max To 0 Step -1
   
   	   For Temp = 0 To B_Loops
   	   	   R = 1
	   	   Delayus R_Delay
	   	   R = 0
	   	   Delayus Max_Time - R_Delay
   	   	   G = 1
	   	   Delayus G_Delay
	   	   G = 0
	   	   Delayus Max_Time - G_Delay
   	   	   B = 1
	   	   Delayus B_Delay
	   	   B = 0
	   	   Delayus Max_Time - B_Delay
   	   Next   

   Next
   
   B_Delay = 0
   
   Goto Main

Where you can get the components;