multi-tasking

[rmteo]

Driving fuel injectors?

More likely simultaneous output of 4 R/C PWM pulses - 1-2mS width, 50Hz frequency.

[malc-c]

More likely simultaneous output of 4 R/C PWM pulses - 1-2mS width, 50Hz frequency.

LOL - on this occasion you're not even warm.....

[tiger_bel]

multi tasking ??? one processor does always one thing.....

quite easy problem:
all depends on your timing - use high speed oscillator (20Mhz)
create a timer under interupt ( interupt 1ms) relaod timer
create counters as much as you need.
increment the counters on interupt and compare with value
if match - relaod counters with new value ...
beware that interupttime is smaller than 1ms !

all other calculations can be done out of interupt.

rgds
tb

[mackrackit]

The only way you can have a PIC do more than one thing at a time is to have part of it done with hardware and the other in code. Sounds like you are going to need to use a timer so it might be doable.

Look at interrupts in general and DT's instant to be specific for ideas.

But do not be embarrassed to tell us about your project, unless...

[Jerson]

Malcolm

Your idea seems to fit the "Soft PWM" concept very well. Search here to find how to do it.

A little pseudo code might show you how

' In a timer interrupt

     DutyCycle = DutyCycle+1
     if DutyCycle < Value1 then
           Port1 = On
     else
           Port1 = Off
     endif
     if DutyCycle < Value2 then
           Port2 = On
     else
           Port2 = Off
     endif
     if DutyCycle < Value3 then
           Port3 = On
     else
           Port3 = Off
     endif
     if DutyCycle < Value4 then
           Port4 = On
     else
           Port4 = Off
     endif

[Acetronics2]

Hi, Malc

The trick is to fire all 4 pulses at the same time ... and use the COMPARE function of a CCP to turn pulses off ...

of course, you must calculate at first which is turned off in 1st, 2nd ...etc.

and load the COMPARE value according to that.

http://mathieu.agopian.free.fr/prog_pic/servoter/

Alain

PS: another way is to use the CCS RTOS tool ... but ... not PbP anymore !

re P.S. ... You have too much things running at the same time, these days ... LOL

[malc-c]

Thanks guys for all your suggestions.

Sorry to be secretive over this project guys, but I'm being mentored / tutored and most of the code so far (99%) has been supplied by that Friend and Mentor so I don't feel that it's appropriate for me to list it here. Hopefully once the festive holiday is over he will be able to assist me further. I'm hoping that once we've got the fundamentals tested and the project is completed we may be able to release the code to the forum community.

His code produces the variable that I have used in my output routine, which I've tested in the real world and now need to replicate 4 times.

I'll take the suggestions and search the forum for information on interrupts.

Many thanks