Voltage issue 16f627a


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  1. #1
    Join Date
    Jun 2011
    Posts
    3

    Default Voltage issue 16f627a

    I have a voltage issue with my project. When portA.0 is taken to +5v, PortB.5 and PortB.6 outputs +5v. When PortA.0 is taken to 0v,GND. PortB.5 and PortB.6outputs 2.7V. I need B.5 and B.6 to go low 0v when A.0 is taken low. I've tried using PortB.7 in place of PortA.0, same results. little help with the program please.

    @ DEVICE pic16F627A, INTRC_OSC_NOCLKOUT


    CMCON = 7
    TRISB = %10000000
    TRISA = %00000011

    start:

    if PORTA.0 = 0 then pivot1
    if PORTA.0 = 1 then pivot2

    pivot1: low 0
    low 1
    low 2
    low 3
    low 4
    low 5
    low 6

    pivot2: low 0
    low 1
    low 2
    low 3
    low 4
    high 5
    high 6
    goto start:

  2. #2
    Join Date
    Nov 2003
    Location
    Wellton, U.S.A.
    Posts
    5,924

    Default Re: Voltage issue 16f627a

    Not sure about Pic Basic, but with PBP it is a good idea to set the pin as a VAR
    low0 VAR PORTB.6
    Dave
    Always wear safety glasses while programming.

  3. #3
    Join Date
    Sep 2004
    Location
    montreal, canada
    Posts
    6,898

    Default Re: Voltage issue 16f627a

    Nah, it won't change anything, HIGH/LOW work as expected. HOWEVER, when you write to consecutive pin, you may want to Write to the whole port, or use a Shadow register. This is to avoid the R-M-W issue.

    PORTB=%11000000

    or

    ShadowRegister VAR BYTE
    '
    '
    ' some code here
    '
    ShadowRegister.7=1
    ShadowRegister.6=1
    'etc etc
    PORTB=SHadowRegister

    Also, make sure all your config fuses are properly set, LVP_OFF, MCLR_OFF (assuming your don't use MCLR pin), OSC (INT or XT, whatever)
    Last edited by mister_e; - 12th June 2011 at 11:21.
    Steve

    It's not a bug, it's a random feature.
    There's no problem, only learning opportunities.

  4. #4
    Join Date
    Jul 2003
    Location
    Colorado Springs
    Posts
    4,959

    Default Re: Voltage issue 16f627a

    Your pivot1 routine "Falls Thru" to the pivot2 routine.
    So the pins will have a 50% dutycycle signal and your voltmeter is averaging them to read 2.7V.

    Just add a goto after pivot1.

    Quote Originally Posted by yasky1 View Post
    @ DEVICE pic16F627A, INTRC_OSC_NOCLKOUT

    start:

    if PORTA.0 = 0 then pivot1
    if PORTA.0 = 1 then pivot2

    pivot1: low 0
    low 1
    low 2
    low 3
    low 4
    low 5
    low 6
    goto start

    pivot2: low 0
    low 1
    low 2
    low 3
    low 4
    high 5
    high 6
    goto start:
    DT

  5. #5
    Join Date
    Sep 2004
    Location
    montreal, canada
    Posts
    6,898

    Default Re: Voltage issue 16f627a



    "Mister E, You want to post less, think more"


    Going back to my batcave...ashamed...
    Steve

    It's not a bug, it's a random feature.
    There's no problem, only learning opportunities.

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