How generate short pulse in spin language ?

Francesco Santandrea · 2008-06-16 16:06

Hello,

this simple spin program generate short pulse at pin 0

CON

_xinfreq = 5_000_000
_clkmode = xtal1 + pll16x

PUB Pulse

dira[noparse][[/noparse]0]:=1

!outa[noparse][[/noparse]0]
!outa[noparse][[/noparse]0]

Why the on time of pulse is so long ? about 20 microseconds (45kHz)

How can generate a short pulse in spin language ?

Thanks

Francesco Santandrea

Francesco Santandrea · 2008-06-16 16:25

Errata corrige

OPS

...
about 20 microseconds (45kHz) ...

is .... about 10 microseconds (100kHz if repeated)...

Rayman · 2008-06-16 16:55

Look here:

http://www.rayslogic.com/propeller/PulseGen.htm

Phil Pilgrim (PhiPi) · 2008-06-16 17:10

Here's a Spin routine that will issue a pulse of any width, beginning at one clock period (12.5ns with an 80MHz clock):

CON

  _clkmode      = xtal1 + pll16x
  _xinfreq      = 5_000_000

  outpin        = 0
  ctra0         = %00100 << 26 | outpin 'NCO with output on outpin.
  frqa0         = 1                     'Increment by 1 on each clock.
  dira0         = 1 << outpin
  

PUB Start | t

  dira := dira0           'Set pin as output.
  frqa := frqa0           'Initialize frqa.
  repeat
    repeat t from 1 to 100 'Pulse widths from 12.5ns to 1.25uS.
      repeat 10000
        Pulse(t)
     
PUB Pulse(t)

  phsa := -t            'Set phsa for pulse width.
  ctra := ctra0         'Start the counter.
  repeat while phsa < 0 'Wait for MSB to go low.
  ctra~                 'Stop the counter.

-Phil

Rayman · 2008-06-16 17:20

That's a nice example!

Francesco Santandrea · 2008-06-16 18:15

RAYMAN Great !!!

Thanks !!!

and if I should be reduced the time between pulses?

Is possible with stop of Cogs ? or otherwise ?

Francesco Santandrea

Rayman · 2008-06-16 19:06

I guess it depends on what you are doing...· What is this for?· Do you want burst or continous output?

jazzed · 2008-06-16 19:24

Phil, your example is great. You should write a book.

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Francesco Santandrea · 2008-06-16 23:56

Rayman

for continuos output

example for

PWM high resolution (10-12 bit and more)
100 - 200 kHz and more

Phil Pilgrim (PhiPi) · 2008-06-17 00:02

Francesco,

To output a 10-bit PWM at 100KHz would require a pulse width resolution of less than 10ns. You won't get PWM output like that with the Propeller. If you don't need true PWM, though, but can settle for the Propeller counter's DUTY mode output, you will come close to your objective.

-Phil

How generate short pulse in spin language ?

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