picaxe 08M sample rate

[linear_shift]

Hi, for how short a time interval can the "pause" command be set? Can it be set as short as the 4 MHz clock? Can the pause command have a float for a variable? I using the picaxe for a/d conversion for a radio astronomy project and need a high DC sampling rate to match (or come close to) the bandwidth of my receiver for the best possible integration time.

Thanks, ls.

 

[Andrew Cowan]

pause = 1ms minimum.

1ms is also about the time taken for each command.

Andrew

 

[wapo54001]

.5ms -- "pause 1" at 8MHz

 

[hippy]

You can use PULSOUT on an otherwise unused pin to get down to 10uS pauses (4MHz) and 5uS (8MHz), although there'll also be a ~200uS overhead for the PULSOUT instruction itself.

 

[tiscando]

You can use PULSOUT on an otherwise unused pin to get down to 10uS pauses (4MHz) and 5uS (8MHz), although there'll also be a ~200uS overhead for the PULSOUT instruction itself.

Why isn't there a 'pauseus' command on all the picaxes and not just the x1 and x2 parts?

 

[hippy]

That's just the way it is. I guess the need for short pauses wasn't perceived as necessary in bygone days and adding that now to earlier PICAXE's would cause all sorts of problems with little gain.

 

[Texy]

.5ms -- "pause 1" at 8MHz

The OP didn't mention which picaxe to use, so why stop at 8Mhz?
If he used X1 parts.......

Manual 2, page 108 :

Pauseus ....

Affect of increased clock speed:
The timebase is reduced to 5us at 8MHz and 2.5us at 16MHz.
Regards,
Texy

 

[hippy]

I using the picaxe for a/d conversion for a radio astronomy project and need a high DC sampling rate to match (or come close to) the bandwidth of my receiver for the best possible integration time.

It would be interesting to know what a high sampling rate is considered to be. At 4MHz the PICAXE can probably sample at around 2,500 times a second but that's without processing any data. Just minimal processing could halve the sample rate though that could be regained using a faster 8MHz or 16MHz.

The sampling rate would very much depend on what processing needed to be done.

 

[Texy]

The OP didn't mention which picaxe to use, so why stop at 8Mhz?
If he used X1 parts.......

Manual 2, page 108 :

Pauseus ....

Affect of increased clock speed:
The timebase is reduced to 5us at 8MHz and 2.5us at 16MHz.
Regards,
Texy

...oooppps - just spotted the title of his message, quoting 08M, so please ignore the above

Texy

 

[Dippy]

Yes, it won't be a super fast sampling rate.

Perhaps, sampleOKE would be quicker than processing in loop.
Then process separately. This also maintains speed of sampling.

PS. There are no floats available.