Square Wave pulses ?

Blackbird455

1. Is there a way to produce square wave pulses with a BS1?

2. What type of wave does the pulsout command produce with a BS2?

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Mike Green

There's no nice neat way to produce square waves with either the BS1 or BS2. You really have to just set up a loop like:

label1:
   high thePin
   goto label2
label2:
   low thePin
   goto label1

The reason for the two labels and two gotos is to balance the execution time in the two halves of the loop.
This example would produce the highest frequency square wave and the frequency would obviously depend
on the model of the Stamp being used. To slow it down, use a pause before each goto. That would get you
a square wave of approximately 500Hz (2ms in the pauses and some time on the order of 100's of us or less
for the statement execution time). You could also add statements other than a pause before the gotos to slow
down the loop, but you'd need to experiment to get just the delay you might need.

The BS1 and BS2 pulsout statements work essentially the same way except for the granularity of the pulse width.
You could use a pulsout statement to an otherwise unused pin to produce the delays needed in the above loop.
This would allow you to easily adjust the square wave frequency by varying the pulsout pulse width, yet give you
a symmetric square wave.

Post Edited (Mike Green) : 9/21/2007 4:51:59 AM GMT

TechnoRobbo

1khz loop - this is the fastest program I have clocked on a BS2:



high thepin

do
toggle thepin
loop

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Have Fun


TR

Post Edited (TechnoRobbo) : 9/21/2007 9:12:02 PM GMT

Blackbird455

Thanks mike,

Is that what I am doing when I toggle the pin high,

for reps 1-30
toggle 2
pause 16

that basically switches it high 30 times with a 16ms pause high and 16ms low right?

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Mike Green

Yes. Actually, the toggle statement is easier to use than high/low as long as you want a symmetric square wave. If you want something asymmetric, separating the high and low functions as I showed is cleaner. You'll need a proper FOR statement:

low 2                ' sets pin to known state
for i = 1 to 30  ' repeat for 15 pulses (15 low->high, 15 high->low)
toggle 2           ' change pin state
pause 16         ' 16ms in each state
next

Blackbird455

Just for grins, What processor will produce nice neat square waves?

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Blackbird455

BTW, mike , I do have the proper FOR statement, Im just on a different computer and couldnt cut and paste.........thanks for pointing it out tho.

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Bean

The SX or the propeller will generate square waves easily. If you use the SX get the SX48, it has 2 hardware timers that can generate square waves without using any processor cycles.

Bean.

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