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?

**flotulopex** · - 24th July 2024, 14:48

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

As Henrik pointed, I'm somehow limited in the number of bytes I can use to address the NeoPixel strings.

Because of the very narrow timings, I cannot use routines to address the strings repeatetely with GOTOs/FOR-NEXTs/GOSUBs and so on. For this reason, I have to write code to address 24 bits for one Pixel in a row and only here, I can repeat the routine with one of the previous mentionned commands. This to say there is not only a timing issue but it is also about code length or space in the PIC.

Having this limitations in mind, I started my project addressing one string at the time and I've got plenty of time to display a minute based clock. Since all strings use the same common code and therefore the same variables, I can only differentiate them using different ports.

So if you mean to have only one NeoPixel string made of (4 digits x 7 segments x 4 Pixels [or LEDs] x 3 bytes per Pixel) + (4 Pixels x 3 bytes per Pixel) = 348 bytes, I can't address them in an array, as far as I understand it.

But what do you have in mind, please?

**Ioannis** · - 24th July 2024, 17:06

There is an easier protocol for addressable LEDs. The APA102 that is not strict on timing.

https://learn.sparkfun.com/tutorials...okup-guide/all

Ioannis

**richard** · - 25th July 2024, 00:44

Having this limitations in mind, I started my project addressing one string at the time and I've got plenty of time to display a minute based clock. Since all strings use the same common code and therefore the same variables, I can only differentiate them using different ports.

a 16f690 has 3 ports A,B and C by different ports do you mean different pins ?

Can all the outputs be on the same port, preferably sequential?
ie RC0:4 OR RC3:7 or similar

**flotulopex** · - 25th July 2024, 07:39

Yes, ports will be in a sequential order.

I'll be using ports:

Seconds: PORTC.3
Minutes Units: PORTC.4
Minutes Thenths: PORTC.5
Hours Units: PORTC.6
Hours Tenths: PORTC.7

16F690 has:
PORTA.0..5
PORTB.4..7
PORTC.0..7

**richard** · - 25th July 2024, 08:37

By changing pinsel var you can select different portc pins
if you need the remaining portc pins then more code is needed

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




pinsel  var byte 
pinsel   = 128 ;  64 FOR RC:6    32 FOR RC:5 ETC 




MAIN:


    PORTC        = PORTC  | pinsel


        ASM
            nop
            nop
            nop
        ENDASM
    PORTC = 0         ' have this syntax for tests only here
        ASM
            nop
        ENDASM
        
    GOTO MAIN
END

**richard** · - 25th July 2024, 08:40

have you tried to light a rgb led strip with a 690 @20mHz yet ?
i have doubts that such a slow chip will do the deed

**Ioannis** · - 25th July 2024, 09:25

Originally Posted by richard

have you tried to light a rgb led strip with a 690 @20mHz yet ?
i have doubts that such a slow chip will do the deed

That's why I proposed APA102 chips. Not strict on the clock frequency.

Ioannis

**flotulopex** · - 25th July 2024, 15:59

have you tried to light a rgb led strip with a 690 @20mHz yet ?

Check this:

**flotulopex** · - 25th July 2024, 16:03

And here's the project's code for now.

**Ioannis** · - 25th July 2024, 16:34

Have not checked al of your code, but in the ***_B routine you include many time the same code. Why not insert it one time and then use GoSub to it? Better efficiency and memory usage.

Also I see you insist on using this difficult protocol. Consider the APA101 as it is less strict and can be used on slow MCUs

Ioannis

**flotulopex** · - 25th July 2024, 16:57

I tried to not repeat the code and use GOTOs or GOSUBS but then, if I do so, the NeoPixel string won't work anymore.

Would the use of an alternative LED string as you mention sove the problem of the ports/code/timing?

I can change for another system but would you have a code snippet to help me started with APA102 please? I've never heard about this one before.h

**Ioannis** · - 25th July 2024, 22:21

Here is a copy of the Richards example.

Code:

'***************************************************************************
'*  Name    : ap102.pbp                                                    *
'*  Author  : richard                                                      *
'*  Notice  :                                                              *
'*          :                                                              *
'*  Date    : 10/11/2017                                                   *
'*  Version : 1.0                                                          *
'*  Notes   :  only tested on pic18 @64 MHZ                                *
'*          : pic18f26k22
'***************************************************************************

#CONFIG
  CONFIG  FOSC = INTIO67
  CONFIG  PLLCFG = ON
  CONFIG  PRICLKEN = OFF
  CONFIG  FCMEN = OFF
  CONFIG  IESO = OFF
  CONFIG  PWRTEN = OFF
  CONFIG  BOREN = SBORDIS
  CONFIG  BORV = 190
  CONFIG  WDTEN = ON
  CONFIG  WDTPS = 32768
  CONFIG  CCP2MX = PORTC1
  CONFIG  PBADEN = OFF
  CONFIG  CCP3MX = PORTB5
  CONFIG  HFOFST = ON
  CONFIG  T3CMX = PORTC0
  CONFIG  P2BMX = PORTB5
  CONFIG  MCLRE = EXTMCLR
  CONFIG  STVREN = ON
  CONFIG  LVP = OFF
  CONFIG  XINST = OFF
  CONFIG  DEBUG = OFF
  CONFIG  CP0 = OFF
  CONFIG  CP1 = OFF
  CONFIG  CP2 = OFF
  CONFIG  CP3 = OFF
  CONFIG  CPB = OFF
  CONFIG  CPD = OFF
  CONFIG  WRT0 = OFF
  CONFIG  WRT1 = OFF
  CONFIG  WRT2 = OFF
  CONFIG  WRT3 = OFF
  CONFIG  WRTC = OFF
  CONFIG  WRTB = OFF
  CONFIG  WRTD = OFF
  CONFIG  EBTR0 = OFF
  CONFIG  EBTR1 = OFF
  CONFIG  EBTR2 = OFF
  CONFIG  EBTR3 = OFF
  CONFIG  EBTRB = OFF
#ENDCONFIG

 led_num  con 3  
 pixels  var byte[led_num * 3]
 pallet   var byte[21]
 apa_global VAR byte bank0       ;global level 0-31
 bit_cnt    VAR byte bank0 
 i VAR byte
 k VAR byte
 j VAR byte
goto overpix
asm 
_showpix 
       movlw    LOW _pixels 
       movwf     FSR2L
       movlw   high _pixels
       movwf   FSR2H 
       movlw 4 
       movwf  _bit_cnt
       movlw 0 
s_frame              ;start frame  4x 00 bytes
       bcf    PIR1,SSPIF
       movwf  SSPBUF
stspi  BTFSs    PIR1,SSPIF       
       bra stspi 
       decf   _bit_cnt
       bnz   s_frame
       movlw _led_num 
       movwf  _bit_cnt
n_led       
       movlw 0xe0
       iorwf _apa_global,W
       bcf    PIR1,SSPIF
       movwf  SSPBUF   ;global led frame
glspi  BTFSs    PIR1,SSPIF       
       bra glspi        
       movf    POSTINC2 ,W   ;blue
       bcf    PIR1,SSPIF
       movwf  SSPBUF
blspi  BTFSs    PIR1,SSPIF       
       bra blspi       
       movf    POSTINC2 ,W   ;green
       bcf    PIR1,SSPIF
       movwf  SSPBUF
gnspi  BTFSs    PIR1,SSPIF       
       bra gnspi
       movf    POSTINC2 ,W    ;red
       bcf    PIR1,SSPIF
       movwf  SSPBUF
rdspi  BTFSs    PIR1,SSPIF       
       bra rdspi
       decf   _bit_cnt
       bnz   n_led 
       movlw   _led_num /8 +1  ;find magic number  of bytes for stop frame
       movwf  _bit_cnt
       movlw 0  
stop_frame                 ;send stop frame
       bcf    PIR1,SSPIF
       movwf  SSPBUF
stopspi  BTFSs    PIR1,SSPIF       
       bra stopspi 
       decf   _bit_cnt       
       bnz   stop_frame
       return 
endasm        
overpix: 
  
    define OSC 64
    OSCCON = %11110000            
    ANSELb = 0
    ANSELA = 0
    ANSELC = 0
    SSPCON1=$20;
    SSPSTAT=$40;
    trisc=%11010111
    apa_global=1  
    latb.0=1  
    trisb=%11111110
    arraywrite pallet,[255,0,0 ,0,255,0 ,0,0,255, 255,255,0 ,255,0,255 ,0,255,255, 255,255,255]
    k=0      ;colour index
    j=0
    gosub shuffle 
    
aloop: 
    call  showpix
    gosub shuffle
    pause  40
goto aloop

And a YouTube video here

Ioannis

**richard** · - 26th July 2024, 00:06

the youtube link is a dud, but i take it that it works even though the timing is a little out of specs

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**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

**flotulopex** · - 4th August 2024, 17:59

I finally made the proto with 5 µC: 1 master and 4 slaves....

Anyway, thanks a lot to all for your help

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**flotulopex** · - 4th August 2024, 18:01

And this is how it looks like for now.

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Thread: Addressing multiple PORTs using one Variable