Products > Test Equipment
Picoscope 2204A streaming mode & trigger Holdoff
markone:
--- Quote from: _Wim_ on December 04, 2022, 08:03:13 am ---
--- Quote from: markone on December 04, 2022, 01:59:27 am ---Please let me know if there is a "trick" to obtain a similar functionality.
--- End quote ---
I would expect you probably can use interval triggering for this (if I understood your requirement correctly). This will trigger on the second falling edge if a large time (time longer than your packet length) has been between the first and the second edge, so you always trigger on the first falling edge of the "new" package. I am however not sure if it will also "see" again the first edge in this new package and retrigger on the next package or you will always mis a package in between. I indeed use this the pico more for analog work instead of protocol analysis.
-snip
--- End quote ---
Finally i had the time to extensively try Interval trigger as you suggested: it works for the purpose but essentially only with certain ratio between horizontal time scale & Trigger "time" parameter, luckily in a way that is compatible with my needs, so problem solved :)
Now i have another question that could be silly for Picoscope's users :
why if i set (i.e.) horizontal scale to 10ms/div and number of samples to 10Ks the resulting sample interval is 10.24us ?
jasonRF:
--- Quote from: markone on December 08, 2022, 01:26:56 am ---
--- Quote from: _Wim_ on December 04, 2022, 08:03:13 am ---
--- Quote from: markone on December 04, 2022, 01:59:27 am ---Please let me know if there is a "trick" to obtain a similar functionality.
--- End quote ---
I would expect you probably can use interval triggering for this (if I understood your requirement correctly). This will trigger on the second falling edge if a large time (time longer than your packet length) has been between the first and the second edge, so you always trigger on the first falling edge of the "new" package. I am however not sure if it will also "see" again the first edge in this new package and retrigger on the next package or you will always mis a package in between. I indeed use this the pico more for analog work instead of protocol analysis.
-snip
--- End quote ---
Finally i had the time to extensively try Interval trigger as you suggested: it works for the purpose but essentially only with certain ratio between horizontal time scale & Trigger "time" parameter, luckily in a way that is compatible with my needs, so problem solved :)
Now i have another question that could be silly for Picoscope's users :
why if i set (i.e.) horizontal scale to 10ms/div and number of samples to 10Ks the resulting sample interval is 10.24us ?
--- End quote ---
The fastest sample rate is 10ns. Each time you increase the time base this goes up by a factor of 2. So you must have done this 10 times since 2^(10) = 1024 and 10ns * 1024 = 10.24 us.
markone:
--- Quote from: jasonRF on December 08, 2022, 02:15:35 am ---
--- Quote from: markone on December 08, 2022, 01:26:56 am ---
--- Quote from: _Wim_ on December 04, 2022, 08:03:13 am ---
--- Quote from: markone on December 04, 2022, 01:59:27 am ---Please let me know if there is a "trick" to obtain a similar functionality.
--- End quote ---
I would expect you probably can use interval triggering for this (if I understood your requirement correctly). This will trigger on the second falling edge if a large time (time longer than your packet length) has been between the first and the second edge, so you always trigger on the first falling edge of the "new" package. I am however not sure if it will also "see" again the first edge in this new package and retrigger on the next package or you will always mis a package in between. I indeed use this the pico more for analog work instead of protocol analysis.
-snip
--- End quote ---
Finally i had the time to extensively try Interval trigger as you suggested: it works for the purpose but essentially only with certain ratio between horizontal time scale & Trigger "time" parameter, luckily in a way that is compatible with my needs, so problem solved :)
Now i have another question that could be silly for Picoscope's users :
why if i set (i.e.) horizontal scale to 10ms/div and number of samples to 10Ks the resulting sample interval is 10.24us ?
--- End quote ---
The fastest sample rate is 10ns. :wtf: Each time you increase the time base this goes up by a factor of 2. So you must have done this 10 times since 2^(10) = 1024 and 10ns * 1024 = 10.24 us.
--- End quote ---
Mmmh, i'm not able to follow your explanation, horizontal time division changes with 1-2-5 sequence like all desktop scope, not in power of 2, the weird thing here is that sample interval is often fractional resulting in "odd" total number of samples.
Let's take the following actual scope setting : 10ms/div -> 100ms full horizontal scale , Sample interval : 10.24us, No Samples : 9766
Why it's not like this : sample interval : 10us, number of sample 10000 ? ???
I fear that in 2204A/2205A sample clock generator is not capable to generate integer sample interval for all time base settings amnd / or there are other trade-off that prevent that ::)
If positive, i'm not happy.
jasonRF:
--- Quote from: markone on December 08, 2022, 01:10:26 pm ---
--- Quote from: jasonRF on December 08, 2022, 02:15:35 am ---
--- Quote from: markone on December 08, 2022, 01:26:56 am ---
--- Quote from: _Wim_ on December 04, 2022, 08:03:13 am ---
--- Quote from: markone on December 04, 2022, 01:59:27 am ---Please let me know if there is a "trick" to obtain a similar functionality.
--- End quote ---
I would expect you probably can use interval triggering for this (if I understood your requirement correctly). This will trigger on the second falling edge if a large time (time longer than your packet length) has been between the first and the second edge, so you always trigger on the first falling edge of the "new" package. I am however not sure if it will also "see" again the first edge in this new package and retrigger on the next package or you will always mis a package in between. I indeed use this the pico more for analog work instead of protocol analysis.
-snip
--- End quote ---
Finally i had the time to extensively try Interval trigger as you suggested: it works for the purpose but essentially only with certain ratio between horizontal time scale & Trigger "time" parameter, luckily in a way that is compatible with my needs, so problem solved :)
Now i have another question that could be silly for Picoscope's users :
why if i set (i.e.) horizontal scale to 10ms/div and number of samples to 10Ks the resulting sample interval is 10.24us ?
--- End quote ---
The fastest sample rate is 10ns. :wtf: Each time you increase the time base this goes up by a factor of 2. So you must have done this 10 times since 2^(10) = 1024 and 10ns * 1024 = 10.24 us.
--- End quote ---
Mmmh, i'm not able to follow your explanation, horizontal time division changes with 1-2-5 sequence like all desktop scope, not in power of 2, the weird thing here is that sample interval is often fractional resulting in "odd" total number of samples.
Let's take the following actual scope setting : 10ms/div -> 100ms full horizontal scale , Sample interval : 10.24us, No Samples : 9766
Why it's not like this : sample interval : 10us, number of sample 10000 ? ???
I fear that in 2204A/2205A sample clock generator is not capable to generate integer sample interval for all time base settings amnd / or there are other trade-off that prevent that ::)
If positive, i'm not happy.
--- End quote ---
Of course you are right - it does not change by a factor of 2 for every time-base setting. Not sure what I was thinking! Depending on the number of samples desired, sometimes it changes by a factor of 4.
But otherwise what I wrote is what the scope does for 'standard' mode. The highest sample rate of the 2204a is 100 MHz (10 ns intervals), and after that it seems to divide the clock down by powers of 2. When using the API you select the sample rate by specifying the power of 2 that divides down that fastest 100 MHz, so this could be a function of the hardware and not just a picoscope software thing. The upshot is that you do not get the exact number of samples that you 'ask' for.
In streaming mode (at least in the picoscope software) it seems to operate differently, in that the highest rate is 1 MHz, and it seems to divide it down by integers (not just powers of 2).
One thing about your example that I don't understand: are you getting more than 8k samples with your 2204a? With your settings I get 4.88 kS at 48.8 kS/s. Or are you using a 2205a (or a hacked 2204a)?
Jason
markone:
--- Quote from: jasonRF on December 08, 2022, 01:49:41 pm ---
-snip
One thing about your example that I don't understand: are you getting more than 8k samples with your 2204a? With your settings I get 4.88 kS at 48.8 kS/s. Or are you using a 2205a (or a hacked 2204a)?
Jason
--- End quote ---
;D
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version