Addressing multiple PORTs using one Variable

**flotulopex** · - 23rd July 2024, 17:06

Hi All,

I need to address five ports conditionally according to the value of one variable.

I found some posts about this subject and hoped this thread would help, but unfortunately, it doesn't.

This a code extract of my current project where timing is crucial and I have to write down a lot of repeating lines of code since FOR/NEXT and GOTOs and GOSUBs take too much time (I'm driving five NeoPixel SW2812B strings with each 28 LEDs/Pixels).

Code:

' PIC 16F690 @20MHz
#CONFIG
    __config _FCMEN_OFF &_IESO_OFF &_CPD_OFF &_WDT_OFF &_HS_OSC &_BOR_OFF &_CP_OFF &_PWRTE_OFF &_MCLRE_OFF
#ENDCONFIG

TRISC = %00000000

DEFINE OSC 20

PortPin VAR PORTA.0
X       VAR BYTE
X       = 23            ' PORTC.7 - "PORTA.0[23]"

MAIN:
    PORTC.7      = 1    ' OK, obviously will work but useless - just make shure the scope works too
    'PORTA.0[23]  = 1   ' OK but useless
    'PORTA.0[X]   = 1   ' No! Makes a blink in the scope and then stays LOW
    'PORTA[X]     = 1   ' No!, nothing happens, pin stays LOW
    'PortPin[23]  = 1   ' OK but useless   
    'PortPin[X]   = 1   ' No!, nothing happens, pin stays LOW
    'PortPin.0[X] = 1   ' No!, error message "Bad variable size modifier: .0"
    '...
        ASM
            nop
            nop
            nop
        ENDASM
    PORTC.7 = 0         ' have this syntax for tests only here
        ASM
            nop
        ENDASM
        
    GOTO MAIN
END

How do I solve this please?

**richard** · - 24th July 2024, 01:13

Code:

    PORTA.0[X]   = 1   ' No! Makes a blink in the scope and then stays LOW

works ok in your loop for me, although it is much slower , period goes from 3uS to 13uS

**Ioannis** · - 24th July 2024, 07:12

"Makes a blink in the scope and then stays LOW"

It will return to low if:

1. you force it somewhere in the program to return to low

2. you PIC is reset for some reason (Watchdog maybe, decoupling cap missing, etc).

Other than these, I see no way to behave like this.

Ioannis

**flotulopex** · - 24th July 2024, 10:03

1. you force it somewhere in the program to return to low

2. you PIC is reset for some reason (Watchdog maybe, decoupling cap missing, etc).

All the code and fuses settings are here.

I soldered the crystal directly on the µC's pins, a 100nF cap is there...

although it is much slower , period goes from 3uS to 13uS

Strange. The pulse should be 800ns (nano seconds).

Okay, I'll give it a try with another 16F690...

**HenrikOlsson** · - 24th July 2024, 10:43

Not sure I understand....
Are you saying that this code works:

Code:

MAIN:
    PORTA.0[23]  = 1   ' OK but useless
    ASM
      nop
      nop
      nop
    ENDASM
    
    PORTC.7 = 0         ' have this syntax for tests only here
        ASM
            nop
        ENDASM
        
    GOTO MAIN
END

And this isn't:

Code:

X VAR BYTE
X = 23
MAIN:
    PORTA.0[X]   = 1   ' No! Makes a blink in the scope and then stays LOW
    ASM
      nop
      nop
      nop
    ENDASM
    
    PORTC.7 = 0         ' have this syntax for tests only here
    ASM
      nop
    ENDASM
        
    GOTO MAIN
END

The 16F690 has an ADC and comparators.
Many of the pins are analog. I don't see you setting them to digital mode. PortC.7 is, however, not one of the analog pins but since you're trying to "index" pins with a variable I suspect PortC.7 isn't the only pin you want to use.

/Henrik.

**flotulopex** · - 24th July 2024, 11:08

Yes Henrik, you might be right.

Keen to keep the code snippet very (maybe too) short here, I removed all others register settings I have set in the original code.

I'll give it also a try...when I'm back from office.

**richard** · - 24th July 2024, 11:31

not really the results i expected, more doubt on proteus ?
i only expected the period to change

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**flotulopex** · - 24th July 2024, 13:16

So Richard,

What is the idea now, then?

Is there any "clean" -meaning software- workaround?

If not, I'll have to make five small independant circuits to each drive his own NeoPixel string, five circuits controlled by a sixth one

BTW, here is how my circuit works with 1 single NeoPixel string.
https://youtube.com/shorts/4fZk9KT4V1M

...still in office now.

**HenrikOlsson** · - 24th July 2024, 13:37

Are you displaying the same "information" on all 5 strings or calculating the "content" for each string on the fly as you go about updating them?
Reason I ask is that 5 strings times 28 LEDs times 3 bytes per LED equals 420 bytes and the 16F690 only has 256 bytes of RAM.

**flotulopex** · - 24th July 2024, 13:43

It is (going to be) a four digits 7 "segments" (each segment is made up of four NeoPixels >> 4x7= 28 NeoPixels per string) wall clock.

The fifth segment is made of 2 or 4 four (not decided yet) NeoPixels and will serve as seconds separator/indicator.

Yes, each string will be uptated specifically, if I can say so.

By now, it all fits in my 16F690 nicely because I address the strings only once at the time or 1x28x3 bytes in total.

**richard** · - 24th July 2024, 14:22

Can all the outputs be on the same port, preferably sequential?

**richard** · - 26th July 2024, 00:10

try this 16 led strip on RC7

Code:

' PIC 16F690 @20MHz
#CONFIG
    __config _FCMEN_OFF &_IESO_OFF &_CPD_OFF &_WDT_OFF &_HS_OSC &_BOR_OFF &_CP_OFF &_PWRTE_OFF &_MCLRE_OFF
#ENDCONFIG
CLEAR
TRISC = %00000000


DEFINE OSC 20
pinsel  var byte 
RED  var byte 
GREEN  var byte
BLUE var byte
px      var byte 
bt      var byte 
pc      var byte 
pinsel   = 128








MAIN:
GREEN=128


asm
        MOVLW 16
        MOVWF _pc
_nxRby        
        MOVF  _GREEN,W
        movwf _px
        MOVLW 8
        movwf _bt
        RLF _px,F
_nxRbt  movf _pinsel,W
        IORWF PORTC ,F
        BTFSS STATUS,C
        GOTO XXR
        NOP
        NOP
        NOP
        
XXR     CLRF PORTC  
        NOP
        RLF _px,F
        DECFSZ _bt,F
        GOTO _nxRbt
        MOVF  _RED,W
        movwf _px
        MOVLW 8
        movwf _bt
        RLF _px,F
_nxGbt  movf _pinsel,W
        IORWF PORTC,F
        BTFSS STATUS,C
        GOTO XXG
        NOP
        NOP
        NOP
        
XXG     CLRF PORTC  
        NOP
        RLF _px,F
        DECFSZ _bt,F
        GOTO _nxGbt
        MOVF  _BLUE,W
        movwf _px
        MOVLW 8
        movwf _bt
        RLF _px,F
_nxBbt  movf _pinsel,W
        IORWF PORTC  ,F
        BTFSS STATUS,C
        GOTO XXB
        NOP
        NOP
        NOP
        
XXB     CLRF PORTC  
        NOP
        RLF _px,F
        DECFSZ _bt,F
        GOTO _nxBbt
        DECFSZ _pc,F
        GOTO _nxRby
        
   
endasm  
 PAUSE 100




GOTO MAIN

**flotulopex** · - 26th July 2024, 15:26

Here's the link for the video again.

Sorry, I'm not the YouTube expert so I hope it works now

**flotulopex** · - 26th July 2024, 15:30

Originally Posted by richard

try this 16 led strip on RC7

Thank a lot Richard. I'll give it a try

**richard** · - 28th July 2024, 04:07

I take it that's a fail. I'm not surprised, the simulator indicated that @20mHz a pic16f690 cannot to a conditional branch quickly enough for a "LOW" pulse for a ws2812

**Ioannis** · - 28th July 2024, 16:37

Now, that is a surprise to me. This is a simple task for a simulator to calculate. It knows clock rate, instruction cycle, why does it fail to make simple calculations?

Ioannis

**richard** · - 29th July 2024, 01:49

Now, that is a surprise to me. This is a simple task for a simulator to calculate. It knows clock rate, instruction cycle, why does it fail to make simple calculations?

the simulator correctly indicated that the code will not work right from the start, the TOH is just out of spec

the code provided was to hopefully prove the outcome one way or the other in real life.
i assume it failed since roger never replied and then went on to ask pic18 questions

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