ikalogic

Open full view…

External sampling clock to SP209i

cajsaf
Fri, 20 Aug 2021 07:44:29 GMT

Could you please tell me the requirements for the external sampling clock? I am transmitting a 1kHz clock from a SQ200 to channel 9 on SP209i and getting a sampling rate of 1,6MHz. What is the minimum frequency allowed? Do I have to change any settings except for "Sampling clock: Ext falling" in ScanaStudio?

Ibrahim KAMAL
Mon, 23 Aug 2021 12:29:35 GMT

Hi, Thank you for your message. I'm not sure I understand what you mean by: > @cajsaf > getting a sampling rate of 1,6MHz Where exactly (and how) do you measure that? Thanks,

cajsaf
Mon, 23 Aug 2021 15:20:25 GMT

Thanks for your answer. I am logging a signal (DCF77 protocol) where the period is one second. According to the measure tool in ScanaStudio, there are 1,6MSa each period.

Ibrahim KAMAL
Mon, 23 Aug 2021 15:53:32 GMT

Ah! 1,6MSa sounds much better than 1,6MHz :) So back to your question: > @cajsaf > What is the minimum frequency allowed? I would say there is no minimum frequency allowed.. as long as the sampling frequency is fast enough for your see (at least) a couple samples during your total capture time. > @cajsaf > Do I have to change any settings except for “Sampling clock: Ext falling” in ScanaStudio? No, in state mode (external sampling clock) that's the only thing you can change: active clock edge. Does that answer your questions?

cajsaf
Tue, 24 Aug 2021 06:34:45 GMT

I may misunderstand the function of the external clock, but if I provide a 1kHz clock, shouldn't I get 1000 samples / second?

Ibrahim KAMAL
Tue, 24 Aug 2021 07:32:08 GMT

well, you would get 1000 sample / second for sure, but the only problem is, ScanaStudio has no way to know the frequency of the external sampling clock. So, when in sampling mode, the time unit is no longer "seconds" but "samples". You cannot do time related measurement in external clock mode. does that make sense to you?

cajsaf
Tue, 24 Aug 2021 08:36:18 GMT

Yes, I understand. But I am logging a signal which has a period of 1 second. So if I use a sampling clock of 1kHz, the time between two positive edges should have 1k samples. But instead I get 1,6M samples.

cajsaf
Fri, 27 Aug 2021 08:33:07 GMT

Do you have any idea why this is happening? If I log a 1Hz signal (Confirmed by logging using the internal 200Mhz clock of SP209i) and using an 1kHz external clock (Also first confirmed by using the internal clock), shouldn't I get 1000 samples between two positive edges of the logged signal? And the CVS file should have a 1000 sample interval in the measurements. Would it be possible for me to send you screen shots or the CVS file to explain what I mean?

Ibrahim KAMAL
Mon, 30 Aug 2021 12:40:30 GMT

Hello, It would be greate the send us *.scana file of the original capture (at 200MHz internal clock) and let us know which signal is to be used as external clock, then we'll try to reproduce this on our end, and move forward from that point. Thank you for your cooperation.