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  1. #1
    Join Date
    Nov 2008
    Posts
    26

    Default Bit Angle Modulation

    Has anyone had any luck with bit angle modulation.
    I have read the forum post that discribes it and come up with the folowing code.

    define osc 4

    ANSEL = %00000000
    CMCON0 = %00000111

    TRISA = %00000000
    PORTA = %00000000
    TRISC = %00100000
    PORTC = %00000000

    led VAR PORTC.0
    bc var byte
    ch1 var byte

    bc = 1
    ch1 = 0

    Main:

    if ch1 <255 then ch1 = ch1 +1

    Gosub leddrive

    GOTO Main

    leddrive:
    for bc = 1 to 8

    select case bc
    case 1
    led = ch1.7
    pauseus 5000
    case 2
    led = ch1.6
    pauseus 2500
    case 3
    led = ch1.5
    pauseus 1250
    case 4
    led = ch1.4
    pauseus 625
    case 5
    led = ch1.3
    pauseus 312
    case 6
    led = ch1.2
    pauseus 156
    case 7
    led = ch1.1
    pauseus 78
    case 8
    led = ch1.0
    pauseus 39
    end select
    next bc
    bc = 1
    return

    end

    This works fine for static values but when ramping up the led flickers as the level increments until after value 128. Any Ideas.

    Thanks

  2. #2
    Join Date
    Feb 2003
    Location
    Sydney, Australia
    Posts
    126

    Default

    I played with it for a while last year, but could never get rid of the steppiness during fades. I used an interrupt routine and the level control was great, but fading showed gaps and all kinds of weird artifiacts.

    In the end I used a pic with three PWM channels to do the control I needed.


    Bill.

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