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1MHz doesn't work with UART at 115200

nbenm
Sun, 10 Mar 2019 10:21:15 GMT

I'm using UART with a SQ200. My device works at 115200, and I can't capture anything at 1MHz. I must use 5MHz. Can someone explain me why. @Ikalogic It would be nice to have topics date and time (in summary)

Ibrahim KAMAL
Sun, 10 Mar 2019 17:56:34 GMT

Hello @nbenm, Thank you for your reply. Usually, we have a rule of thumb: having a sampling rate that is at least 10 times higher than the baud rate. When you say you can't capture anything at 1 MHz, do you mean that you can't "decode" ? Could you send me a capture of what you get at 1MHz in a *.scana file?

nbenm
Sun, 10 Mar 2019 19:00:37 GMT

Thanks @Ibrahim At 1MHz Scanaquad stays waiting for trigger. Nothing happens. At 5MHz I have signal and it is correctly decoded. But it does it for a small amount of time. When talking about UART time is usually quite long. That's why I would like to configure 1MHz. Even then it's not enough.

Ibrahim KAMAL
Sun, 10 Mar 2019 19:12:50 GMT

Aha, so you're using a trigger, that may explain it. What kind of trigger are you using?

nbenm
Sun, 10 Mar 2019 20:00:02 GMT

I use a trigger on string

Ibrahim KAMAL
Sun, 10 Mar 2019 22:46:07 GMT

Thank you for this info. That explains a lot. The trigger sequence generator need timings that are precise enough with respect to BAUD rate (this depends on the way each script is implemented). I would recommend using an edge trigger for the timebeing. Untill then, i'll see if the UART plugin script can be optimized in a way to let the trigger sequence work the way you want.

nbenm
Sun, 10 Mar 2019 22:48:10 GMT

Nice thanks. I'll wait until you tell me if it's possible to optimize the plugin.

Ibrahim KAMAL
Sun, 10 Mar 2019 22:49:35 GMT

could you send me the *.scana workspace with your trigger configuration to support@ikalogic.com ? this will help me quickly get to the point and reproduce the same behavior you have on your end. Thanks!

nbenm
Mon, 11 Mar 2019 07:47:33 GMT

@Ibrahim With edge trigger it works fine even at 250kHz! So trigger needs really to be optimized. I have sent you the workspace.

nbenm
Mon, 18 Mar 2019 17:52:52 GMT

@Ibrahim do you have some news?

Ibrahim KAMAL
Fri, 22 Mar 2019 19:36:41 GMT

Hi! Sorry, i was on a fair in Paris all week, will get back to you ASAP.

nbenm
Tue, 02 Apr 2019 20:16:04 GMT

Hi Ibrahim, Any news ?

Ibrahim KAMAL
Tue, 02 Apr 2019 20:24:25 GMT

Hi nbenm, Your first question is why trigger does not work at 1MHz or below. I have dug into the UART script and the reason why is that the trigger sequence for a UART string is a sophisticated time-constrained sequence of edges. To reach required timing precision, the device must use a sampling rate that is high enough. I know that "high enough" is not very clear or precise, and that's why in the new version of ScanaStudio (and the new scripting system) we will provide more information and insight to help the user see the limits of the system, and remove the guess work. Thank you,