DS1054Z Rs232 decoding - Page 1
Forum section: electronics / testgear

author: nealfox
author_rank: Contributor
timestamp: February 28, 2018, 03:04:57 pm
content: I am having problems performing Rs232 decoding with my new DS1054Z. While I have years of experience using analog scopes I’m new to digital scopes and protocol decoding. So, I’m trying to determine is I have a problem with my scope or with me.I am generating a serial stream using an Arduino Uno and capturing it as a single-shot. As I start examining it everything is fine but at some point, as I change the horizontal position the decode breaks up. Also sometimes changing the timebase effects the decode.

author: m_t
author_rank: Contributor
timestamp: February 28, 2018, 03:39:44 pm
content: Unfortunately, there is no way to fix this. The RS232, I2C and SPI decoders on the 1054Z all stop working if your timebase setting is too large. Also, the list view only decodes the waveform currently shown on the display. This can be pretty annoying if you have to "scroll" through a long single shot capture.

author: Fungus
author_rank: Super Contributor
timestamp: February 28, 2018, 03:58:12 pm
content: Yep. It has a lot of limitations.It's good for finding out if RS232 is working correctly or not but it's not a serious tool for hacking or examining long data sequences.(Use your Arduino for that...)

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: February 28, 2018, 04:03:41 pm
content: That's correct, but in the 2nd image the rigol should have lost only the first "o" in the "o-p-q..." sequence, not everything up to the "A-B..." as it did, no?

author: nealfox
author_rank: Contributor
timestamp: February 28, 2018, 04:27:16 pm
content: That was my thought. Both screen shots are from the same single-shot capture. So the data is the same and just turning the position control shouldn’t have affected it at all.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: February 28, 2018, 04:48:56 pm
content: Never thought about it before, but now I wonder if a real UART would also take/need so many chars to get in sync again... Who knows? Anybody?

author: Karel
author_rank: Super Contributor
timestamp: February 28, 2018, 05:07:22 pm
content: One possibility is to use DSRemote. It will do the serial protocol decoding offline using the whole internal memory of your scope (12 or 24Mpts).It doesn't suffer from the fact that the scope fails to decode correctly when the start of the visible trace is in the middle of a character.

author: Adrian_Arg.
author_rank: Frequent Contributor
timestamp: February 28, 2018, 05:55:12 pm
content: for windows is there any software?

author: nealfox
author_rank: Contributor
timestamp: February 28, 2018, 05:56:37 pm
content: This is my first attempt at serial decoding and I didn’t know what to expect. I naively assumed that I would be able to simply scroll through the entire serial message. I haven’t even started to explore DSRemote so I guess that’s my next project. Thanks everybody for your help.Neal

author: Karel
author_rank: Super Contributor
timestamp: February 28, 2018, 06:50:43 pm
content: Quote from: Adrian_Arg. on February 28, 2018, 05:55:12 pmIf you want you can use DSRemote on windows by using VirtualBox.

author: Fungus
author_rank: Super Contributor
timestamp: March 01, 2018, 12:36:22 am
content: Quote from: nealfox on February 28, 2018, 05:56:37 pmIt's a natural enough assumption.However, you'll find that almosteverythingthat these DSOs do is basedonlyon the data shown on screen. They don't have the processing power to work on the entire 24Mb internal buffer for their calculations (and usually not even a direct access to the sample memory...)Serial decoding simply follows this pattern of using the on-screen data. It's the way things work.

author: LaurentR
author_rank: Frequent Contributor
timestamp: March 01, 2018, 06:46:16 am
content: If you are going to be playing with Arduino-type microcontrollers, do yourself a favor and get at least a cheap USB logic analyzer (e.g. a Saleae clone - or a real one if you have the budget)They are able to record very long streams of UART/i2c/SPI and decode with ease (and have typically have many more decoders than any scope). Some can look at analog signals at the same time. You can also cross-trigger with the DS1054Z.The DS1054Z is barely usable for serial decode and even better scopes that decode from full memory are limited in what they can acquire and for how long vs. external USB LAs. Obviously, the USB LAs have much lower acquisition rates, but that tends to be enough for basic serial protocols.

author: Karel
author_rank: Super Contributor
timestamp: March 01, 2018, 07:34:38 am
content: Quote from: LaurentR on March 01, 2018, 06:46:16 amThe problem with logic analyzers is, is that they use 1-bit ADC's. You risk to loose a lot of time by searching for a logic errorin your sourcecode while in reality the problem is caused by bad signal integrity...

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: March 01, 2018, 08:04:07 am
content: Quote from: Karel on March 01, 2018, 07:34:38 amExactly!

author: Fungus
author_rank: Super Contributor
timestamp: March 01, 2018, 08:16:29 am
content: Quote from: GeorgeOfTheJungle on March 01, 2018, 08:04:07 amAnd ... that's what the DS1054Z is for!!The serial decode on the DS1054Z isn't much use for decoding huge amounts of information but it's plenty good enough to check out the signal integrity.

author: Karel
author_rank: Super Contributor
timestamp: March 01, 2018, 08:48:49 am
content: Quote from: Fungus on March 01, 2018, 08:16:29 amAnd that's why DSRemote can be usefull.