Synchronous pulses

[AndrewC]

.. not sure if that is the correct title but want I want to do is output a pulse in parallel on three different pins. The pulses will be of different lengths (1msec down to a few usecs) and the leading edges need to be aligned.

I can think of one way of doing it - put all 3 o/p's high together then pause incrementally as I bring them back down one at a time - but I was wondering if there was a more elegant way of doing it ?

Thanks,

Andrew

[Jerson]

Are you thinking of a software PWM? Quite easy to do really.

http://darreltaylor.com/DT_INTS-14/SPWM.html

[AndrewC]

Are you thinking of a software PWM? Quite easy to do really.

http://darreltaylor.com/DT_INTS-14/SPWM.html

No, not a software PWM.
Actually for controlling some photographic strobes.
Three command lines, need to fire simultaneously but then shut off after different times and wait for the next trigger.

Andrew

[mackrackit]

Add a little to your idea... Assuming the pins in question are on the same port...

TRIS? = %00000000
X VAR BYTE
Y VAR BYTE
Z VAR BYTE

STROBE:
PORT? = %00000111
PAUSE X  ' Or use PAUSEUS
PORT? = %00000011
PAUSE Y
PORT? = %00000001
PAUSE Z
PORT? = %00000000
RETURN

[Acetronics2]

Hi, Andew

It's in French ... Yes.

But just close to what you look for ...

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

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

Alain

[AndrewC]

Hi, Andew

It's in French ... Yes.

But just close to what you look for ...

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

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

Alain

Hi alain,

Yes, seems to be pretty much what I'm describing. Thanks for the link.

Andrew

[AndrewC]

Reply to Dave:

Yup, that's what described.

The issue is that the three outputs will not always be ordered longest to shortest from bit 0 to bit 2 (or bit 2 to 0 as you ordered them). Not difficult to get around - just need to sort the pulse lengths, calculate the incremental time between sequential trailing edges and use a bunch of IF statements to pull them back down in the right order.

But woudn't it be nice if there was single command that could output parallel pulses

Andrew

[mackrackit]

How are you going to input the parameters to the PIC?