| Products > Test Equipment |
| USB logic analyzer - what's the current "favorite" for ~150$? Hantek 4032L? |
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| abyrvalg:
A quick and dirty setup touching an FPGA devboard's 100MHz oscillator pad with HT4032L's test lead shows no problems acquiring a 100MHz signal. 400MS/s, 1M samples gives a stable 262144 (1MiB/4 exactly) edge count regardless of the channel used (tried A0 and A15 on the opposite sides of the connector). I have no generator to test higher frequencies quickly, but I'll cook some FPGA config for this (among with some pattern generation to test the external clocking). Edit: 262144 is the number of periods, not edges (I had both measurements turned on). |
| maginnovision:
--- Quote from: abyrvalg on July 17, 2018, 02:56:12 pm ---A quick and dirty setup touching an FPGA devboard's 100MHz oscillator pad with HT4032L's test lead shows no problems acquiring a 100MHz signal. 400MS/s, 1M samples gives a stable 262144 (1MiB/4 exactly) edge count regardless of the channel used (tried A0 and A15 on the opposite sides of the connector). I have no generator to test higher frequencies quickly, but I'll cook some FPGA config for this (among with some pattern generation to test the external clocking). --- End quote --- Try 20MS and attach a screenshot. |
| abyrvalg:
Yeah, getting the false edges now, 10485800+-2 instead of 10485760, both A0 or A15. |
| abyrvalg:
DSLogic's result: stable 9998362 edges in 20M samples (DSLogic's M is 10^6, not 2^20). Unrelated clocks runaway? Funny, it took more time to get the edge count from DSLogic's "polished" software. You can't set a measurement cursor to the first/last sample just by dragging it to the edge - on the left side it happily goes to some hidden negative time area and gets lost there, on the right side you need a highest detail zoom to reach the edge and then the measurement refuses to count the edges silently (solution: it doesn't like the right cursor being at the last sample, move it left a bit). |
| toli:
The clocks are definitely not matched well enough to get absolute accuracy at such long record length. The only question is at what point you can see missed edges over a limited period of time. To get "perfect" sync you'll need to sample with the external clock pins. Edit: just in case it wasn't clear what I meant to say, I'll add a few more words. If the clocks are even 1ppm out, you will get 1 cycle missed over 1Mcycles of these clocks. So this is absolutely understandable that the number isn't the round number you expect. However, if you can find the ratio of the two clocks by sampling a signal that is low enough in frequency so that it is always detected properly, you can count on this ratio to remain almost unchanged for a short period of time. You can then use this info to try ramping up the input frequency until the counted number deviates noticeably from the expected number with the actual frequency ratio of the two instruments. |
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