PIC's ports individual bits manipulation - how to?

[sayzer]

Hi flotulopex,

Check this http://www.picbasic.co.uk/forum/showthread.php?t=3753

May give you some ideas.


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[flotulopex]

Thank you sayzer,

I found this thread already. I tried Melanie's way but it doesn't work.

First, it looks as "Digit" won't increment from 0 to 3.

Second, I have put a "spy" before entering the loop. I put PORTA.6 = 1.

Since I use PIC Simulator, I can see the port status and as soon as the program has started, PORTA.6 goes back to 0 (!?).

Am I doing something wrong?

In my code's FOR...NEXT loop, I have put:

    for Digit = 0 to 3
        value_d = value dig digit
        lookup value_d, [$7E,$0C,$B6,$9E,$CC,$DA,$FA,$0E,$FE,$DE], Segments
        PORTA.0(Digit) = ~DCD Digit
        PORTB = Segments
    next

[skimask]

    for Digit = 0 to 3
        value_d = value dig digit
        lookup value_d, [$7E,$0C,$B6,$9E,$CC,$DA,$FA,$0E,$FE,$DE], Segments
        PORTA.0(Digit) = ~DCD Digit
        PORTB = Segments
    next

I'm not so sure that ~DCD Digit will work. I could be wrong. Maybe: ~ (DCD Digit) ?
And I don't see an initial 'ENABLE' in the program itself...not sure if that's needed either or if interrupts are 'ENABLE'd by default.
Ha...just found the answer to that last 'not sure'. Page 183 of the PBP manual states that interrupts are NOT enabled by default...so, you have to turn them on.

[SteveB]

How about something simple, like:

PORTA.0 = Digit.0
PORTA.1 = Digit.1
PORTA.2 = Digit.2
PORTA.3 = Digit.3

HTH,
SteveB

[flotulopex]

I just made this piece of code as test.

MYPORT  var PORTA
Loop    var BYTE
PORTA.0 = MYport.0
PORTA.1 = MYport.1
PORTA.2 = MYport.2
PORTA.3 = MYport.3

PORTA.6 = 1 'Test to check port's state change in simulator...

Start:
    for LOOP = 0 to 3
        myport.0[Loop] = 1  'High
        myport.0[loop] = 0  'Low
    next
    goto start
END

It works except the PORTA.6 will change it's status from 1 to 0 when the firt loop will be executed.

[skimask]

I think you've got the variable declarations backwards.
Try myport.0 = porta.0, etc. instead of the way you have it.

[mister_e]

this won't work indeed... and you make it too complicated for what it need to be.

Start:
    for LOOP = 0 to 3
        PORTA.0[Loop] = 1  'High
        PAUSE 500
        PORTA.0[loop] = 0  'Low
    next
    goto start
END

MyPORT.0=PORTA.0 will work only once, If you want to alias a variable bit to a PORT bit... it's an all different story..

[flotulopex]

I've attached two pictures about what I can see.

The first picture "Before Loop Start" shows that my PORTA.0 to 3 are set to "1". This is because I need them to be at this state before the main loop starts (driving CA Leds).

I did the same for PORTA.6 (=1) just for testing purpose. PORTA.6 will be used for something else in my program if I can handle the actual problem.

When I start the execution of the program, PORTA.6 goes to "0" witch is unwanted here.

Mister_E you're right, using DCD will modify all ports.... Was not a good idea on my side. Thank you for making me aware.

[mister_e]

PORTA.0(Digit) = ~DCD Digit

as you write to a BIT, it have to be 0 or 1 ONLY.

Use a LCD or a serial comm to see the results of ~DCD digit... it return 254, 253, 251, 247.

i bet PORTA.0[Digit]=1 is what you're looking for.