What's the best code loop-structure to handle multiple tasks without interruption?

[OldMarty]

Hi All,

I'm looking for help on the best way to structure code that has multiple tasks happening, while not interrupting or slowing the overall operation at any given time.
For example, i want to drive 16 LEDs using a 4x4 (Multiplexed) matrix (4 rows x 4 columns)
The LEDs in the matrix will be often changing states and/or flashing in various patterns.

The LED status and flash speeds will be dependent on settings of various pots and switches wired to the PIC.
The LED patterns vary from switching approx 10-20 times per second down to say once per second, while other LEDs are just static ON or off.
Of course the 'ON' LEDs need to look like they're stable, not flickering due to the speed of the matrix scanning being interrupted by the code going to process a pot-change etc.

In my past attempts (long ago), while my projects have worked overall, i suffer too much interruption to the LEDs while adjusting pots and setting external switches to alternate values.
So, in all, i need to master how i use loops to monitor/switch everything cleanly. Are there preferred ways to do this?
My loops in the past have always revolved around goto's & gosubs, i've never ventured into using DO loops or WAITs, WENDs etc...maybe this is what i'm lacking?

I haven't provided code for my example, as this is just an open question about general structure and loop techniques (rules of thumb) that people use for speed efficiency.
Before you ask, it's now slow hardware or slow chips, it's *me* not structuring my looping and I/O monitoring correctly.

Any suggestions are greatly welcomed, i can only learn what i've been doing wrong all these years lol ;-)

Regards,
Marty.

[richard]

You can always drive the leds like this charlieplex [12 led] example . the multiplexer is an interrupt driven background task that only uses about
2% of the processing time [if I remember correctly]. the isr could be done in asm if speed critical

'****************************************************************
'*  Name    : charlieplex.pbp                                        *
'*  Author  : richard                                   *
'*  Notice  :                                *
'*          :                                *
'*  Date    :                                          *
'*  Version :    16f1825     @3.3 volts                               *
'*  Notes   :       *
'*          :              *
'*            
'****************************************************************
  
#CONFIG
             __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_ON  &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
              __config      _CONFIG2, _PLLEN_ON & _LVP_OFF
#ENDCONFIG

DEFINE OSC 32
 
 include "dt_ints-14.bas"
 Include "REENTERPBP.bas"
 

asm      
INT_LIST macro     
      INT_HANDLER TMR1_INT, _TOCK, PBP ,YES
      
      endm
       INT_CREATE
ENDASM       
      
       
   
     
@timer1 =TMR1L
leds var word
tmp var byte
x var byte
timer1         VAR WORD EXT
timer1=15543
T1CON=$31
@ INT_ENABLE  TMR1_INT
OSCCON=$70
ANSELA=0
ANSELC=0

   
mainloop:
leds=1365    
pause 1000 
leds=2730
pause 1000  
goto mainloop  
 
   
    
     
  
TOCK:
T1CON.0=0
timer1=timer1+64536
T1CON.0=1
if leds.0[x] then
    lookup x,[12,12,9,9,3,3,5,5,6,6,10,10],tmp
    TRISC =(TRISC&$f0)|tmp
    lookup x,[ 2, 1,4,2,8,4,8,2,8,1 ,4, 1],tmp
    latC =(latC&$f0)|tmp
endif
x=x+1
if x=12 then x=0
@ INT_RETURN

[OldMarty]

I guess what i'm really asking is how to setup my loop(s) in an order from most-used tasks (update LEDs) to least-used tasks (read pots/switches) and process them all in a way that keep it running smooth and not flickering.

This is for ALL my coding in future projects, not just limited to a LED chaser as per my initial example.

I want to master "correct structure" to keep my code running efficiently. (please don't suggest C or asm, it's my structure that needs to be revised, not the platform i program with, my coding will STILL be crappy & flickery in C or asm lol)

[richard]

produce some code and post it for comment

[tumbleweed]

...LEDs need to look like they're stable, not flickering due to the speed of the matrix scanning being interrupted by the code going to process a pot-change etc.

You might be looking at this the wrong way around and have the stuff you're doing in the interrupt and the main loop backwards.

I usually reserve using interrupts for events that must be done at a high priority, and leave the not so important things that aren't as time sensitive and can wait a bit for handling in the main loop.

For example, the matrix scanning would be done by a timer ISR running fast enough to do the scanning w/out producing any flickering (like Richard's charlieplexing routine)
All the other stuff would be done by polling in the main loop ie looking for key press, reading knobs, etc. That way no matter what your main loop is doing the matrix scanning always gets done when it needs to.

[OldMarty]

You might be looking at this the wrong way around and have the stuff you're doing in the interrupt and the main loop backwards.

I usually reserve using interrupts for events that must be done at a high priority, and leave the not so important things that aren't as time sensitive and can wait a bit for handling in the main loop.

For example, the matrix scanning would be done by a timer ISR running fast enough to do the scanning w/out producing any flickering (like Richard's charlieplexing routine)
All the other stuff would be done by polling in the main loop ie looking for key press, reading knobs, etc. That way no matter what your main loop is doing the matrix scanning always gets done when it needs to.

Yes, perhaps i was looking at it all "backwards" hence my overall question of how people prefer to keep busy code running smoothly ;-)