Fast Loop in PICBASIC Pro

[paul borgmeier]

I agree with Steve (and everyone else) that the hardware PWM sounds best for what you described. But, if it will not work for you consider "unrolling" your loops like that shown below. You lose no time in looping but it does cost you more code space (16 repeats is not huge considering the amount of memory in the 877A).

DEFINE OSC 20
TRISB.0 = 0
PORTB = 0

PORTB.0 = 1   ' I = 1 (on for 12.6 uS)
@ nop
Pauseus 12
PORTB.0 = 0   ' (off for 12.4 uS)     
PAUSEUS 12

PORTB.0 = 1   ' I = 2
@ nop
Pauseus 12
PORTB.0 = 0     
PAUSEUS 12

;(more of the same here)

PORTB.0 = 1   ' I = 16
@ nop
Pauseus 12
PORTB.0 = 0     
PAUSEUS 12

Endhere:
goto Endhere
END

[mister_e]

could be...

DEFINE OSC 20
TRISB.0 = 0
PORTB = 0
pauseus 0 ' do nothing good but include PAUSEUS?C macro
TRISB.0 = 0
PORTB = 0
start:
asm
    CHK?RP PORTB
    local a=0
    while a<16        
        BSF PORTB,0
        nop
        PAUSEUS?C 12
        BCF PORTB,0
        nop
        PAUSEUS?C 12
a+=1
    endw
endasm
pause 100
goto start

now play with the a < x value, and look what happen to your code size.. interesting eh?

Now compare the code size of

PORTB.0 = 1   
@ nop
Pauseus 12
PORTB.0 = 0     
@ nop
PAUSEUS 12

copy and pasted 16 times, with the one generated with my solution... mmm interesting

Sometime MPASM directive are really handy!

EDIT: you could also use

@   local a=0
@   while a<16
        PORTB.0=1
        @ nop
        PAUSEUS 12
        PORTB.0=0
        @ nop
        PAUSEUS 12
@a+=1
@       endw

If you don't like the PAUSE?C, BSF, BCF option... both generate the same code.

[paul borgmeier]

Steve, I did compare code space

171 for 16X of my block (MPASM)

211 for your code as posted
191 (with the second nop removed from yours - which makes T = 25 uS)

it is interesting.

Now, the question for me is how the ASM while directive checks without adding time???

EDIT (after looking up while) - I see .... it doesn't check .... now I understand your comment about code space and it is a handy directive :-) THANKS

[mister_e]

MIIP, there's something weird... if i use a 16F877 and this....

DEFINE OSC 20
DEFINE LOADER_USED 1
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 129 ' 9600 Baud @ 0.16%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically


pauseus 0
TRISB.0 = 0
PORTB = 0
start:
asm
    CHK?RP PORTB
    local a=0
    while a<16        
        BSF PORTB,0
        nop
        PAUSEUS?C 12
        BCF PORTB,0
        nop
        PAUSEUS?C 12
a+=1
    endw
endasm

pause 100
goto start

it compile 207 Word

if i use...

DEFINE OSC 20
DEFINE LOADER_USED 1
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 129 ' 9600 Baud @ 0.16%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically


pauseus 0
TRISB.0 = 0
PORTB = 0
start:
    ' #1
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #2
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #3
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #4
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #5
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #6
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #7
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #8
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #9
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #10
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #11
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #12
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #13
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #14
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #15
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

    ' #16
    PORTB.0 = 1   
    @ nop
    Pauseus 12
    PORTB.0 = 0     
    @ nop
    PAUSEUS 12

pause 100
goto start

Still 207 words...

EDIT: OK DUDE we hit the button at the same time or...so.