Indexing Port Pins

[Demon]

Update: Cleaned up logic so LEDs always get same current no matter how many are in use.

When you need to blink a lot of LEDs:

Here's the results of a current test using 32 LEDs on a 18F44K22 using internal oscillator at 64MHz.

portLedA    var     PORTA       ' Define Ports
portLedB    var     PORTB
portLedC    var     PORTC
portLedD    var     PORTD
portLedE    var     PORTE

byteLoop    VAR     byte        ' Define variables
byteDelay   VAR     byte

byteActiveA var     byte        ' Define active pins
byteActiveB var     byte
byteActiveC var     byte
byteActiveD var     byte
byteActiveE var     byte

byteRXA     var     byte        ' Define RX data
byteRXB     var     byte
byteRXC     var     byte
byteRXD     var     byte
byteRXE     var     byte

    portLedA = %00000000        ' Initialize Leds off
    portLedB = %00000000
    portLedC = %00000000
    portLedD = %00000000
    portLedE = %00000000

 byteActiveA = %11111110        ' Determine Active pins     Pin A.0 not used
 byteActiveB = %11111111
 byteActiveC = %00111111                                  ' RX / TX in use
 byteActiveD = %11111111
 byteActiveE = %00000111                                  ' MCLR input only

     byteRXA = %11111110        ' RX data from Master PIC
     byteRXB = %11111111                                    
     byteRXC = %00111111
     byteRXD = %11111111
     byteRXE = %00000111

byteDelay    = 35               ' Tweak this value to control current and frequency

' 1 LED active        668 Hz     2.7 mA LED    14.2 mA circuit
' 32 LEDs active      668 Hz     2.7 mA LED    99.0 mA circuit

' Using 2N2222 NPN transistor, 4K7 base with 680K pull-down,
'       LED direct to collector from 5VDC.

mainloop:

    For byteLoop = 0 to 7                       ' Go through 8 bits
        if byteActiveA.0[byteLoop] = 1 then     ' Check if pin is used
            portLedA.0[byteLoop] = byterxA.0[byteLoop]
            PAUSEUS byteDelay
            portLedA = %00000000                ' Faster than setting bit to 0
        endif
        if byteActiveB.0[byteLoop] = 1 then
            portLedB.0[byteLoop] = byterxB.0[byteLoop]
            PAUSEUS byteDelay
            portLedB = %00000000
        endif
        if byteActiveC.0[byteLoop] = 1 then
            portLedC.0[byteLoop] = byterxC.0[byteLoop]
            PAUSEUS byteDelay
            portLedC = %00000000
        endif
        if byteActiveD.0[byteLoop] = 1 then
            portLedD.0[byteLoop] = byterxD.0[byteLoop]
            PAUSEUS byteDelay
            portLedD = %00000000
        endif
        if byteActiveE.0[byteLoop] = 1 then
            portLedE.0[byteLoop] = byterxE.0[byteLoop]
            PAUSEUS byteDelay
            portLedE = %00000000
        endif
    Next byteLoop

    Goto mainloop           ' Go back to loop and blink LEDs forever

Use byteActiveA-E variables to determine which bits you want toggled.

Use byteRXA-E variables to receive bits from a Master PIC.

Use byteDelay variable to tweak current and LED brightness.


For my testing, MCLR (can only be input), RX/TX (needed) and A0 (unused) were disabled.

Robert