Uart decode from digital lines

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neil.macmullen
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Uart decode from digital lines

Post by neil.macmullen » Wed Feb 13, 2019 3:03 pm

Having just received my 2208BMSO first impressions are that the hardware is great, the software... not so much (I may write a proper post on the this later). I'm really only using the scope as a logic analyser at this stage and the first thing I wanted to do was log some UART traffic using the MSO. I've previously been using PulseView (free) with a cheap Hobby I/O box which does this very nicely but can't export the decoded traffic.

I have set up two digital lines to capture RX/TX transitions. The documentation suggests these can be turned into a UART decode using Tools/Serial Decoding. First suprise is that this only does one line at a time (rather than Tx/Rx pair) but I guess I can see the logic. It's disappointing though that the claimed "in-view" decode doesn't appear in the digital sub-view even if I select "display packets in ... graph". Maybe this is a bug?

It also seems very odd that clicking on a line in the "serial decoding" window doesn't automatically scroll the digital view to that instant. Is there any way to do that?

Since I'm actually decoding AT traffic what I'd really like is the ability to layer some packet-grouping above the raw character decode (i.e. show start-end time for sequences ending '\r'. Is this possible?

Thanks,
Neil

Gerry
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Re: Uart decode from digital lines

Post by Gerry » Thu Feb 21, 2019 11:47 am

Hi Neil,

Sorry for the delay in responding. We can't always get to forum posts as timely as we would like.

I regret that your not impressed with our PicoScope 6 software. I would be curious to know if the reason is that you were expecting a more full-featured Logic Analyzer. If so, then bear in mind that our hardware/software combination gives you a full-featured Oscilloscope, with optionally huge amounts of storage for captured data, and tools to perform detailed measurements of all of it, along with complex triggering, tools to clean up the signal and improve it further, and transform it Mathematically, tools to capture rare events or events that detract from the norm, different degrees of automation from alarms to Macros, a Spectrum analyzer with different ways of displaying the frequency content of the captured data, all in addition to a means to see the digital equivalent of captured Serial Protocols (and this is not a complete list of the capabilities). So, what we have here are tools for analyzing in huge detail, different aspects of Analogue signals, including what they look like digitally, but what we don't have are tools that can perform a multitude of functions on Digital data once it has been decoded, such as what you would find in a Dedicated Logic Analyzer, because that would be a different product.

Regarding your "first surprise", if when you say "this only does one line at a time (rather than Tx/Rx pair)", you mean that it only displays one channel at a time in the Serial Decoding Table then the answer is yes, at any one time you're going to be deciphering the message/data in one packet, but you can easily flip backwards and forwards between complimentary packets of interest on the Rx and Tx lines, and you can have the same decoded information available to view simultaneously in the graph view (as shown in the 'Example simultaneous Rx Tx' data file and screenshot below), so you actually can view an Rx and Tx decoded pair.

Example simultaneous Rx Tx.psdata
(1.78 MiB) Downloaded 12 times
Example simultaneous Rx Tx.PNG

If when you say "the claimed "in-view" decode doesn't appear in the digital sub-view", you are referring to the 'In view' option mentioned in a video that is online demonstrating RS232 serial decoding, then that is because it is an old video showing a previous version of our software. There is no need for the in-view option because the data is available by default in the graph and in the Serial Decoding Table, and you can just double click on the table data to immediately scroll to the equivalent data in the graph view (which answers your point on scrolling).

I'm not quite sure what you mean by your last point. Could you explain that in more detail with reference to the different views (or just one view, if that is what you mean).

Regards,

Gerry
Gerry
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neil.macmullen
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Re: Uart decode from digital lines

Post by neil.macmullen » Thu Feb 21, 2019 12:59 pm

Gerry,
Thanks for the response - no problem on the delay as I have been away myself. My initial frustration with the software is mostly around some of the non-intuitive aspects of getting it to do 'easy' things. It took me at least 30 minutes of trial and error to get a serial decode displayed whereas I had Pulseview up and running in about 5 minutes. Clearly Picoscope is far more powerful but there are several areas where I think it's easy-of-use could be improved. As I say, I'll write a separate post explaining some of those in more detail.

I do take your point about the product being aimed more at analysing analogue signals but we purchased it primarily to review digital bus activity - the ability to double-check analogue behaviour is just a nice bonus! (I.e. we saw PicoScope as being a more capable and fully-featured replacement for the Hobby-scope/Pulseview combination we were previously using.) That's not a complaint - I'm just trying to explain the reason I come at from a "logic analyser" viewpoint.

>If when you say "the claimed "in-view" decode doesn't appear in the digital sub-view"

I notice that the picture you attached shows the decode in the analogue chart view (views->subview->analogue). Since I was/am trying to use the device to look at digital signals I had closed this view and had opened the digital view (views->subview->digital). The Serial decode does _not_ display in this subview which is the kind of non-intuitive behavior I was referring to earlier! (In fact, I had assumed the digital streams wouldn't even appear in the analogue view!)

>you can just double click on the table data to immediately scroll to the equivalent data in the graph view

Thanks - I should have thought to try _double_ clicking - I was expecting the cursor to follow the highlighted item or for there to be a right-click context menu.

>I'm not quite sure what you mean by your last point.

The traffic I am capturing on the serial bus is AT traffic to a celluar modem. So, for example we might transmit "AT+CGMR\r" and receive "9.02\r" It's hard to read that when displayed as a table of individual character rows (as in the serial decoding table) or 'buslines' (in the analogue view). What I'd like to be able to do is provide an optional decode layer that groups characters separated by newlines so that a single rown in the table would show "AT+CGMR\r" or the 'busline' in the analogue view would contain the string "AT+CGMR\r". I'm quite happy to write software to do this using the SDK but it's a bit unclear to me if it's possible to add this kind of capability using the SDK or whether client code is limited to processing data outside of the picoscope UI?

Neil

Gerry
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Re: Uart decode from digital lines

Post by Gerry » Fri Mar 01, 2019 10:17 am

Hi Neil,

Could you post a psdata file of your capture, so that we can see what you are referring to.

Regards,

Gerry
Gerry
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neil.macmullen
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Re: Uart decode from digital lines

Post by neil.macmullen » Fri Mar 08, 2019 5:00 pm

Gerry - I'm not sure the forum notifications are working? My settings here _say_ I should receive notifications but I do not see any from your replies.


There is a file attached showing some AT traffic on lines 12 and 15.

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