Multi-Threading

[Jumper]

So we have one led you want to flash in a fading way.

How frequently do you want to flash it?

Do you want to do other stuff while flashing the LED? In that case what will the PIC do?

Can you put the LED on PORTB.3?

How fast do you want to fade it up and down?

How smooth do you need it, how many steps would you like the led to have on the way up and down?


Before we even try to untangle the code for this it would be nice to know that you can use this pin and get the other information as well.

/me

[skimask]

Can you put the LED on PORTB.3?

I'd doubt it...
http://www.picbasic.co.uk/forum/showthread.php?t=9275
Check post #32 and #33!

[Ted's]

Jumper if you want to design a code example do not stick to values, stick to variables instead. Frequency should be f. Other concurrent thread(s) exist while fading in/out. There is no data available about them yet. Just use "LED", I'll use a pointer to the right port like LED VAR PORTX.Y. Speed of fading should be a function of frequency. Freqency means: every 1/f seconds there is a change. If LED is off, Led_fade_routine starts and vv. Led_fade_routine consists of fade_in_time = 2/f and fade_out_time = 2/f. Smoothness depends on OSC. Should be as smooth as possible, ie chunks_duration should be at a minimum.

Thanks for your initiative. I appreciate that.

[Jumper]

Did I miss something? In my code example I have LED as an alias for a port and I can't see I use any other values than T1CON (which is a register).

If you are referring to my question about moving the LED to PORTB.3 it is only because I wanted to know if it was possible, and in that case we could use the HPWM for the fading. Doing that way would take very little instruction time and still give a nice fading effect since we only need to change the dutycycle once in a while to get a very smooth fading effect.

I am deeply sorry that my poorly written code example upset you.

over and out

/me

[Melanie]

Ted stop winding people up that are trying to help you. Folks give up their time for free around here. If you don't like an answer then be polite, say "Thank You" to acknowledge the time they may have devoted to potentially a lost cause, and move on.

In case you're not aware... the short answer to your question at Post #1 is Yes.

If yor PIC has ADC, Comparators, CCPM, USART etc the you can SIMULTANEOUSLY perform any or all of those functions whilst doing something else altogether AT THE SAME INSTANT IN TIME. Go do a forum SEARCH, this has been discussed before.

Alternatively you can TIME-SLICE your code... in the simplest form, using your flashing LED for example, say the LED is flashing at a 2Hz rate, you can switch ON your LED, then go do something else for 250mS before you need to devote an instruction to switching it OFF Gee... at 4MHz, that's a shed load of instructions you can carry out whilst that LED is ON, and again when it's OFF. To the casual observer, it will appear as if the PIC is doing multiple tasks.

[peterdeco1]

How would you use the ADCIN command to read the value of a pot while simultaneously doing something else?

[Bruce]

Setup a hardware peripheral like capture, hardware PWM, counter, UART, etc and enable
it. They will all run simultaneously in the background while you're sampling the A/D input.

[Security]

Hello. I am using the instant interrupt routine. I also posess a servo motor like ted,
so I wand to start a pulsout every 20ms. I did this in the tmr0-interrupt routine(tmr0
initialized by OPTION_REG = 1) I am using a 20Mhz quarz.

I think: 20 / 4 = 5Mhz. OPTION_REG means prescaler = 1:1. Means 1/(5,000,000) equals 0.2us.

TMR0 = 8Bit => 256 * 0.2us = 51.2us.

So every 51.2us there will be an interrupt. So

20,000 / 51.2 = 390.625 = 391. So as soon as the interrupt will have occurred 391 times 20ms
should have been passed. I wrote

  main:
   '...do xyz
   counter = 0
   END

  IRRoutine:
   IF counter = 391 THEN
    pulsout servo, duration
   ENDIF
   IF counter > 391 THEN
    counter = 0
   ENDIF
   IF counter < 391 THEN
    counter = counter + 1
   ENDIF
   @ INT_RETURN

But the servo is choppy. What is wrong?