PortD mistery


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Thread: PortD mistery

  1. #1
    Join Date
    Mar 2009
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    Latina, Italy
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    Default PortD mistery

    Hi, I'm just going mad. Wish somebody could help.
    I'm making a tracked rover using a PIC16F877/20 and the classical SN754410.
    I've got the H-Bridge connected to portd 0-6, separate 12 volts power for the motors, capacitors and so on.
    I double checked everything about 30 times but only one of the two motors runs in both directions, (pin 2-3), the one connected to pin 0-1 only goes one way.
    After all day measuring, checking, using multimeter etc, I just moved the control on portc and everything works smoothly.
    I can't really understand why.
    By the way, I tried with another SN754410 (just in case...), another 877 (just in case), I swapped motors.
    I mean, everything was OK.
    Any idea of where is my mistake? (I'd like to sleep tonight)
    Tx.

  2. #2
    Join Date
    Jul 2003
    Location
    Colorado Springs
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    Default

    About the only thing that can interfere with PORTD on an 877, is the Parallel Slave Port (PSP).

    Occasionaly people will set TRISE = %11111111 thinking it sets PORTE to all INPUT. But it actually turns on PSP mode on PORTD, because Microchip used the extra bits in TRISE for something other than TRIS.
    <br>
    DT

  3. #3
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    Mar 2009
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    Default

    I actually set TRISE=00000000
    It shouldn't be that.
    Any other idea?

  4. #4
    Join Date
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    I actually set TRISE=00000000
    Surely you meant TRISE=%00000000

    Al.
    All progress began with an idea

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