Our Prof. ordered us to purchase one Siglent SDS1104X-E... - Page 1
Forum section: electronics / testgear

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 23, 2019, 07:05:30 pm
content: Hello everyone,Our Prof. ordered us to purchase one Siglent SDS1104X-E. It's planned to buy at least a dozen of scopes for the student's laboratory.Before making decision about buying the rest of scopes, we have to, so to speak, assess the potential of purchased Siglent.A task is a troubleshooting of misbehaving communication between laboratory equipments (Prof's design, by the way). The Prof. himself got tired of this annoying malfunction.So we have on the table brand-new scope right now.Could anyone guide us (step by step) how torecordRS485 packets and analyze if they are ok?Then we would like todecodesent command from the master and an answer from the slave.As a side note, we have to record a lot of the same packets. Since the slave answers very rarely with not distorted characters.As far as we understand, in order to get what happens we have to catch at least one not distorted answer from the slave for further comparison and analyzing.What we want to record is in the attachment.Thanks in advance

author: tautech
author_rank: Super Contributor
timestamp: May 23, 2019, 07:12:47 pm
content: Please check the firmware version as there is brand new firmware released yesterday that addresses some Decode issues/bugs.Links here:https://www.eevblog.com/forum/testgear/siglent-sds1204x-e-released-for-domestic-markets-in-china/msg2431869/#new

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 23, 2019, 07:32:13 pm
content: Quote from: tautech on May 23, 2019, 07:12:47 pmWe have 8.1.6.1.26 on board. Do you advise to perform an update at once?they uploaded no user manual, but two service manuals instead. SDS100X-E. Could you look?

author: tautech
author_rank: Super Contributor
timestamp: May 23, 2019, 07:44:34 pm
content: Quote from: CiscERsang on May 23, 2019, 07:32:13 pmLatest version is 6.1.33.Check the release notes as there is several improvements for DecodeQuoteYou can download any documentation here:https://www.siglentamerica.com/resources/documents/digital-oscilloscopes/#sds1000x-e-seriesScroll down until you see the 1000X-E listings.

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 23, 2019, 07:59:18 pm
content: Quote from: tautech on May 23, 2019, 07:44:34 pmYes, I was there. Could you tell them that they confused and put two services manuals. There's no user manual under link calleduser manual. You can check that.

author: tautech
author_rank: Super Contributor
timestamp: May 23, 2019, 08:18:47 pm
content: Quote from: CiscERsang on May 23, 2019, 07:59:18 pmOK I see.You can get the user manual here:http://old.siglentamerica.com/USA_website_2014/Documents/manual/SDS1000X-E_UserManul_UM0101E-E03A.pdf

author: tv84
author_rank: Super Contributor
timestamp: May 23, 2019, 08:38:00 pm
content: Quote from: CiscERsang on May 23, 2019, 07:05:30 pm@tautech, with this prof your life is simplified!

author: tautech
author_rank: Super Contributor
timestamp: May 23, 2019, 08:42:25 pm
content: Quote from: tv84 on May 23, 2019, 08:38:00 pmWe make little gains in brand awareness every day.But some days.........

author: tv84
author_rank: Super Contributor
timestamp: May 23, 2019, 08:45:06 pm
content: Quote from: tautech on May 23, 2019, 08:42:25 pmMaybe it's simpler in the southern hemisphere...

author: Rerouter
author_rank: Super Contributor
timestamp: May 24, 2019, 04:46:56 am
content: I personally know of 2 Local Tafe's that refused upgrading to new DSO's because they where not aware of the EDUmode stuff to prevent students cheating by just pressing autosetup, so there is probably more business out there for you Tautech. (EDU mode can disable any combination of the autosetup Key, the Measure Menu or the Cursors Menu)As for the RS485, I'll be getting home this afternoon, I'll have a look, its likely to be using the UART decoder. if its a normal RS485 connection then it can be wired to look like a 0-5V single ended signalhttps://www.stratusengineering.com/rs232-rs422485-conversion-cable-connection-requires-no-external-electronics-power/

author: plurn
author_rank: Regular Contributor
timestamp: May 24, 2019, 05:36:20 am
content: Quote from: CiscERsang on May 23, 2019, 07:05:30 pmI don't know how to do this. But there is some good information (a tutorial) from rf-loop on working with serial decode and history buffer starting at this post which might provide some help:https://www.eevblog.com/forum/testgear/siglent-sds1204x-e-released-for-domestic-markets-in-china/msg2096347/#msg2096347

author: Fungus
author_rank: Super Contributor
timestamp: May 24, 2019, 06:50:43 am
content: Quote from: tautech on May 23, 2019, 07:12:47 pmReally?

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 24, 2019, 08:52:31 am
content: Quote from: tv84 on May 23, 2019, 08:45:06 pmnot sure, the Prof himself came from Europe (quite famous EU tech. uni) and saw there a classroom equipped with Siglents. So, he just had got a peek, I guess.

author: Rerouter
author_rank: Super Contributor
timestamp: May 24, 2019, 10:30:20 am
content: Ok, a Guide,- Switch on- Press green "Default" key, (this just ensures I'm not fighting other settings from before)- Rotate the "Vertical" knob to set channel 1 to 2V / Div- Rotate the "Trigger Level" knob to 2V- Rotate the "Horizontal" knob to fit atleast 1 full communication cycle on the screen, even if there is a big dead gap between the 2 packets, it will be recorded- Rotate the "Horizontal Position" kbob so the blue triangle at the top of screen is lined up with the right edge of the first division (what you see on the screen is what is decoded,- Press the "Decode" button (It should default to Decode 1, UART)- Use the Third from the left UI button at the bottom of the screen to Enter the "Signal" menu- Use the second from the left UI button at the bottom of the screen to Set "Threshold"- Rotate the "Adjust / Intensity" Knob to make "Threshold" 2V- Press the 6th UI Button to go back 1 menu- Press the 4th UI button to enter the "Configure" menu- Use the Second Button to set "Custom"- Rotate the "Adjust / Intensity" Knob to make "Custom" match the "Baud Rate" you are using for your project.... Continue for the other parameters for your project, this part I'm sure you can flesh out- Use the 6th UI button to get to the 2nd pag of the "Configure" menu..... Continue Setting your Idle level and bit orderDone,

author: Fungus
author_rank: Super Contributor
timestamp: May 24, 2019, 04:16:06 pm
content: Quote from: Rerouter on May 24, 2019, 10:30:20 amThe following users thanked this post:tautechLooks like everybody here has overlooked step 1 of the task (i.e. the difficult part).

author: tv84
author_rank: Super Contributor
timestamp: May 24, 2019, 04:35:19 pm
content: Quote from: Fungus on May 24, 2019, 04:16:06 pm@Fungus, enlighten us, please.

author: plurn
author_rank: Regular Contributor
timestamp: May 24, 2019, 05:26:52 pm
content: Quote from: tv84 on May 24, 2019, 04:35:19 pmUmmm.. Connect the probes to the correct places maybe?

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 24, 2019, 08:13:08 pm
content: Quote from: Rerouter on May 24, 2019, 10:30:20 amunboxing;powered up;FW was updated to ver. 6.1.33;warmed up;self-calibration was performed according to manual;all probes were marked with corresponding coloured rings and compensated;CH1 was hung on line B+;CH2 was hung on line A-;Press green "Default" key, (this just ensures I'm not fighting other settings from before);Rotate the "Vertical" knob to set channel 1 to 2V / Div;Rotate the "Trigger Level" knob to 2V;Further troubles begin...Rotate the "Horizontal" knob to fit atleast 1 full communication cycle on the screen, even if there is a big dead gap between the 2 packets,it will be recorded;The point is... Due to master features... in short, it can't send packets continuosly. It works like: a corresponding button is pressed --> instantly very short transmission occurs. An example:6E 75 6D 62 72 3F 0A. That meansNUMBER?LF.Then, in less then 10ms the slave answers (half-duplex works this way). An example:1B 0D 0A. That means27CRLF.Is there a way to catch an entire packet? As it's seen, it's very short.

author: Rerouter
author_rank: Super Contributor
timestamp: May 24, 2019, 11:21:00 pm
content: I do not know your baud rate, so lets say set horizontal to 2ms/Div, the scope has lots of sample points, so it may appear rather small, I should then add I suppose after setting up the decodersCan you find out your baud rate,So for Mk2 so farCode:- Switch on- Press green "Default" key, (this just ensures I'm not fighting other settings from before)- Rotate the "Vertical" knob to set channel 1 to 2V / Div- Press the "2" button to Turn on the second channel- Rotate the "Vertical" knob to set channel 2 to 2V / Div- Rotate the "Horizontal" knob to 2ms / Div- Rotate the "Horizontal Position" knob to -12ms- Rotate the "Trigger Level" knob to 2V- Press the "Normal" button for the trigger- Press "Utility" button- Press "Next Page" until your at page 4/4- Press "Reference Position"- Press "Horizontal" to set it to fixed position- Press the "Decode" button (It should default to Decode 1, UART)- Enter the "Signal" menu- Press "RX" and set to "CH2"- Press "Threshold", Rotate the "Adjust / Intensity" Knob to make "Threshold" 2V- Press the 6th UI Button to go back 1 menu- Enter the "Configure" menu- Use the Second Button to set "Custom", Rotate the "Adjust / Intensity" Knob to make "Custom" match the "Baud Rate" you are using for your project.... Continue for the other parameters for your project, this part I'm sure you can flesh out- Use the 6th UI button to get to the 2nd pag of the "Configure" menu..... Continue Setting your Idle level and bit order- Use the Back button to return to the main decode menu- Ensure "Display" is set to "On- Press next Page- Press on "List"- Press on "Display" and set to "Decode 1"- Press the back button- Press "Format" and change it to "ASCII"- Run your Device once, the scope should trigger and there should be data on screen- Press on the "Horizontal" knob to enter zoom mode- Rotate the "Horizontal" knob twice clockwise to set the text at the top center of the screen to "500us/"- Rotate the "Horizontal Position" knob to -12ms- Continue Rotating the "Horizontal" knob clockwise until the first message is clearly visable on screen- Trim with "Horizontal Position" as neededThis is the master message, the decoder will be on the bottom showing what ASCII it has decoded, the list display at the top hopefully makes it clearer, but sometimes you will need to zoom in furthur for it to show up nicely at the bottom- Rotate the "Horizontal" knob Counter-clockwise, back to "500us/"- Rotate the "Horizontal Position" knob to set to roughly -1ms- Trim and zoom back in as required to show the response message clearly on screen, its the same as above, you may have to zoom in a bit furthur for it to show up nicely on the bottom.Fungus, I'm still not clear what you think I am missing, you cannot decode on the math trace, If that is what you are trying to get at. If the OP wants me to flesh out all the decoder settings, I will need him to at minimum follow the guide without the decoder section for me to see his waveform and work out the settings.

author: TK
author_rank: Super Contributor
timestamp: May 25, 2019, 12:10:12 am
content: Try using segmented memory to catch both transmission and reception in separate segments, use normal trigger mode

author: nctnico
author_rank: Super Contributor
timestamp: May 25, 2019, 12:42:56 am
content: I think one of the things getting in the way is Siglent's dreaded automatic memory depth selection. If you zoom out at higher samplerates there is no more data to show. Fixate the memory depth to maximum and set the time/div to a value so you can trigger on the first packet and still have time to capture the reply.

author: nez
author_rank: Regular Contributor
timestamp: May 25, 2019, 02:31:35 am
content: FYI @CiscERsang, just in case you hadn't seen it, the link for the newest user manual has been corrected (I assume it was fixed after you guys tried it).The updated manual for the new firmware (6.1.33) is:UM0101E-E03Bhttps://www.siglentamerica.com/wp-content/uploads/dlm_uploads/2017/10/SDS1000X-E_UserManual_UM0101E-E03B.pdf(Note the 'B' )I believe the previous firmware (6.1.26) uses manual version:UM0101E-E03A(shown as UM0101X-E03A inside the doc's title page for some reason)

author: plurn
author_rank: Regular Contributor
timestamp: May 25, 2019, 03:41:25 am
content: Quote from: CiscERsang on May 24, 2019, 08:13:08 pmIf you are connecting near the master slave devices (short distances), you might be able to get away with connecting to only one of those lines since they are are the same signal with one inverted as your diagram shows. That could free up some memory. Only the polarity of one of them will match up with the decode setting you pick I think you just need to pick the right one. If it was long distances involved, you would probably need some external converter to un-invert and combine them to remove noise and then still only measure a single line on the oscilloscope.I guess you could separately measure both lines without decode to make sure the signals look properly inverted to make sure that is not an issue.https://www.csimn.com/CSI_pages/RS-485-FAQ.htmlQuote from: CiscERsang on May 24, 2019, 08:13:08 pmSee my earlier post Reply#10linking to a tutorial on using history buffer (Segmented memory as mentioned by TK). Should allow you to capture lots of packets.Or - if you don't want to read everyones suggestions and join the dots for yourself, just get a Siglent sales engineer to do your homework for you with the promise of a big order if they get it right.

author: Fungus
author_rank: Super Contributor
timestamp: May 25, 2019, 08:42:34 am
content: Quote from: tv84 on May 24, 2019, 04:35:19 pmRS485 is a differential bus, you don't just connect a probe to a wire to diagnose it.Quote from: plurn on May 24, 2019, 05:26:52 pmWhich would be....?

author: Rerouter
author_rank: Super Contributor
timestamp: May 25, 2019, 09:44:35 am
content: RS485 under controlled conditions with a ground lead provided can be done with just 1 wire, add external noise e.g. in a vehicle or complicated installation and you would be correct.The SDS1104X-E does not let you decode on the math trace, so to treat it like a proper differential bus would require an external RS485 to UART or similar converters, like I linked in an image earlier.The third alternative if the RS485 device is battery powered or not ground referenced. Connect your scope ground lead to Data- and the scope channel 1 signal to Data +, this way it is treated deferentially. done this many times with vehicle Canbus / J1708 (which is RS485)

author: nctnico
author_rank: Super Contributor
timestamp: May 25, 2019, 10:06:17 am
content: Quote from: Rerouter on May 25, 2019, 09:44:35 amUART (serial) signals over RS485 always need a ground reference because UART signals have a varying DC component.

author: tautech
author_rank: Super Contributor
timestamp: May 25, 2019, 10:45:21 am
content: Quote from: Rerouter on May 24, 2019, 04:46:56 amDo you have the secret key presses for this or some SCPI command you've discovered ?I ask as I've asked the factory on this matter and got no reply.Reply via PM if required.TIA.

author: Rerouter
author_rank: Super Contributor
timestamp: May 25, 2019, 10:55:27 am
content: Nothing secret about it, I've posted it in the main thread like 3 times so far, But I can understand it is a lot to parse at once.If you change any settings, e.g. "EDUMODE Autosetup, OFF" the menu will appear and you can change it via the UI if you prefer, otherwise it is buried,Even factory defaulting the scope or reloading a setup will not change it, only with those SCPI commands,

author: tautech
author_rank: Super Contributor
timestamp: May 25, 2019, 11:04:27 am
content: Quote from: Rerouter on May 25, 2019, 10:55:27 amTotally missed anything you've bought to our attention before.And you know I'm always here and like to think I don't miss much but for this I need a goodThanks heaps, added to my archives.

author: tv84
author_rank: Super Contributor
timestamp: May 25, 2019, 12:49:19 pm
content: @Rerouter, thanks.BTW, what stops a student from issuing the command himself to disable the EDU MODE? The scope would need to be disconnected from the grid...What about issuing SCPI commands via the USB disk scripting (a crafted .ADS) ? Have you investigated any of this?

author: Rerouter
author_rank: Super Contributor
timestamp: May 25, 2019, 01:28:49 pm
content: I'm going to go out on a limb that If a kid is familiar enough with test gear to find info on that command and re-enable them, he is more than smart enough to figure out how to do things without those controls,After all they would not even tell a dealer about it, and things get buried on these forums really easily, If your that kid in the future having found this thread, God Speed you clever bugger

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 25, 2019, 08:28:26 pm
content: Quote from: Rerouter on May 25, 2019, 09:44:35 amPlease take a look at how does that a quite ancient oscilloscope. True, it's continuos transmission. Thegreenone ismathfrom differential signal (red/yellow).Firstly, I need to get similar oscillogram, to analyze. Probably it won't come to decoding.Do you mean it's not possible to get something useful (decode) from thegreenone? Or?

author: tautech
author_rank: Super Contributor
timestamp: May 25, 2019, 08:46:19 pm
content: First just plain forget about needing Math in SDS1104X-E for data bus analysis !Connect probes to data lines and the ground/reference clip to an appropriate signal ground point.Ensure trigger is set to Auto.Adjust scope to get appropriate displayed signal amplitude.Use trigger settings to get thestartof any packet appearing on the horizontal trigger point....this may need the use of some trigger Holdoff so the scope cannot trigger again until afteranypacket. Use the scopes Holdoff virtual keyboard to make large adjustments rather than use the encoder.Set trigger rise/fall to match the first edge of the data packet.Then give us a screenshot showing something of the bus traffic and we can advise the next settings.

author: tautech
author_rank: Super Contributor
timestamp: May 27, 2019, 12:30:24 am
content: OK so I've had a little research and play with my SDS1104X-E.Note display settings used plus the now invisible 3ms Holdoff used to prevent retriggering within a packet.RS485 is in many ways a similar differential protocol to 2 wire CAN so a few examples using CAN from my STB-3.Some Math on the 2 wire CAN signalsWith Zoom we can have a large number of packets on the main window and scroll through them using the Zoomed window using Hor Pos control however we can't use Math in this manner.If we use Zoom and Decode there are no such restrictionsWith all the bells and whistles activated we have the list with packet #75 representing the first post trigger packet and all the others accessible using the scroll control to examine the full list.

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 29, 2019, 08:32:24 pm
content: hello everyone,all this time we were struggling with connection to WEB interface. First we desided to use TP-Link 725N (we borrowed that stuff), for some reasons it showed very bad results. We will try it again withtiny stuff, just to see what a reason might be. We saw WEB-page, however it was loading so slowly (perhaps it is just router issues).So we desided to go the other way. We ordered thistiny stuffhttps://mikrotik.com/product/RBmAPL-2nD. I would say it's a piece of work.However, we were able to tame that stuff and now we can continue our bus troubleshooting.to be continued...

author: tautech
author_rank: Super Contributor
timestamp: May 29, 2019, 10:03:18 pm
content: Quote from: CiscERsang on May 29, 2019, 08:32:24 pmFor tips on successful connection to the WEB interface watch this vid from ~1min in:https://youtu.be/Cxh_Liay09E

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 30, 2019, 10:00:49 pm
content: Quote from: tautech on May 25, 2019, 08:46:19 pmhello everyone,Finally we managed to catch a query/answer with your help.Off the top of my head there are visible signs of voltage level mismatching between query and reply. Either drivers are powered up with different voltage levels, or in case if voltages are equal, that might be a lack of biasing.the supply voltage of slave's driver I will be able to measure.the supple voltage of master's drive is not possible to measure, because of sealed master's case. It may make a query regarding drive's supply voltage to manufacturer, though.your opinions please.Web-server is

author: nctnico
author_rank: Super Contributor
timestamp: May 30, 2019, 10:42:02 pm
content: Looking at these pictures I think that the slave is responding too quickly and/or something else is going on. The signals don't look OK at all and it is no surprise the communication isn't working reliably.

author: tautech
author_rank: Super Contributor
timestamp: May 30, 2019, 11:51:48 pm
content: Yes, in that signals are at different levels is confusing and the idle levels are neither high or low but it seems this is just how RS485 is based on the timing diagram posted earlier.CommentsAny visible distortion is insufficient to affect proper bus operation.It might appear the supply voltages to each device are mismatched and so the levels are different. An adjustable PSU supplying the slave might be useful to find a match between device traffic levels.Use probes and inputs set to 10x in order to reduce the capacitive load 1x probes place on the signal bus.Change V/div to Coarse with a press of the V/div encoder.Use the blue Print button to capture USB screenshots and in doing so you can have an appropriate menu showing to give more info on the settings used.Adjust code to give a wait time before the slave replies.

author: nctnico
author_rank: Super Contributor
timestamp: May 31, 2019, 12:11:17 am
content: Quote from: tautech on May 30, 2019, 11:51:48 pmYou are definitely wrong here. This is RS485 on a short distance so we should see nice rectangular waves with messages from each side having a consistent amplitude. This is not the case in what the OP is showing and that should be fixed first. If the bus is driven by more than one device on a bus then there is not way to tell what the other side will receive. There can be all kinds of circuitry in between the RS485 driver and the bus as well.

author: tautech
author_rank: Super Contributor
timestamp: May 31, 2019, 12:16:14 am
content: Quote from: nctnico on May 31, 2019, 12:11:17 amPlease read the following line:Quote from: tautech on May 30, 2019, 11:51:48 pm

author: nctnico
author_rank: Super Contributor
timestamp: May 31, 2019, 12:31:40 am
content: Look more closely at the signal. It is not about the base levels but there are also distorted pulsed in there at the beginning of the reply. A tell-tale sign something is wrong on an RS485 bus. I'd like to see a much cleaner start.

author: tautech
author_rank: Super Contributor
timestamp: May 31, 2019, 12:52:45 am
content: Quote from: nctnico on May 31, 2019, 12:31:40 amYeah of course:Quote from: tautech on May 30, 2019, 11:51:48 pm

author: TurboTom
author_rank: Super Contributor
timestamp: May 31, 2019, 07:33:22 am
content: @CiscERsang -I'm quite surprised that there are those needle pulses in the distorted signal screenshot. The RS485 drivers shouldn't be able to produce these, especially since they are differential and not common-mode. Can you zoom in on them to better get an idea of their shape? It's well possible that you've got a problem with the termination on the line. Maybe one of the terminators is dodgy, or if they are actively switched, have a look at the switch / control signal. The common-mode DC offset between sent and received signals wouldn't bother me too much, this appears to be well within the common mode range of the typical RS485 line transceivers.Cheers,Thomas

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 31, 2019, 08:35:16 am
content: @tautech,An update:- the first one: distortion while receiving;-the second one; receiving is ok. I wouldn't say that it occurs sporadically. It's misbehaving almost constantly. For example, within fifty transmissions/measurements it's possible to see a single good event.it looks like slaves' transmission begins too early. Don't it?

author: TurboTom
author_rank: Super Contributor
timestamp: May 31, 2019, 08:43:16 am
content: Thanks @CiscERsang, but what I meant to have magnified (VERY magnified) is the tiny spike, just a pixel wide in your screenshots, indicated here, since it looks really awkward and it shouldn't be there:

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 31, 2019, 08:49:35 am
content: Quote from: TurboTom on May 31, 2019, 08:43:16 amI've got you, I saw those tall "needle" spikes towards each other. I'm just figuring out how to capture that in a better way.Give me a few minutes.

author: TurboTom
author_rank: Super Contributor
timestamp: May 31, 2019, 09:23:20 am
content: Just press the time base knob (sec/div) to enter zoom mode, turn it to the required magnification and use the horizontal shift (trigger delay) knob to move the highlighted area to the spike.

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 31, 2019, 09:25:28 am
content: Quote from: TurboTom on May 31, 2019, 09:23:20 amcross-posted see #46

author: tautech
author_rank: Super Contributor
timestamp: May 31, 2019, 09:42:45 am
content: Quote from: TurboTom on May 31, 2019, 08:43:16 amDecoupling do you reckon ?

author: tautech
author_rank: Super Contributor
timestamp: May 31, 2019, 09:54:12 am
content: Quote from: CiscERsang on May 31, 2019, 08:49:35 amYou have extra channels that you could connect one to the slave power rail to check rail behavior with timing correlation to the spike.

author: TurboTom
author_rank: Super Contributor
timestamp: May 31, 2019, 10:09:39 am
content: I'm almost certain that it's not a decoupling issue. It wouldn't explain the output voltage of one of the lines swinging ~1.5V below ground. To me, it much more looks like the transmitter of the first sequence doesn't get disabled fast enough before the answering node enables its transmitter, causing the two transmitters to "fight" each other momentarily. When the first transmitter finally gets disabled, the considerable current flowing through the line callapses and causes an inductive spike - that's what we see here and what will perfectly well explain the opposite polarity.To solve the problem requires either delaying the answer to be sure the (first) transmitter is disabled or to look at the transmitter's code to make sure it gets disabled immediately after it finished its transmission. It may also just be a configuration issue, i.e. node1 is configured to send 2 stop bits while node 2 expects only 1 stop bit and thus starts its transmission too soon.Cheers & good luck,Thomas

author: tautech
author_rank: Super Contributor
timestamp: May 31, 2019, 10:23:05 am
content: Thanks Tom, yeah that sorta points to what Nico and I were saying earlier....the code needs fixing.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 01, 2019, 02:56:42 pm
content: Quote from: tautech on May 30, 2019, 11:51:48 pmoddly enough, but the manufacturer sweared that master's transceiver is powered up by 5.0V. I, in turn, measured slave's transceiver power supply voltage,it's 5.0V.Quote from: tautech on May 30, 2019, 11:51:48 pmfor educational purposes, tell me please, what 's useful menu that should have been appeared after pushing thebluebutton. I had nothing noticed except making screenshots function.thank you!

author: tautech
author_rank: Super Contributor
timestamp: June 01, 2019, 08:04:58 pm
content: Quote from: CiscERsang on June 01, 2019, 02:56:42 pmSure but you can see master and slave levels are slightly different, whether that makes much difference to the thresholds each use for communication is another matter.Quote from: CiscERsang on June 01, 2019, 02:56:42 pmYou have been using the Save feature and there's no need to for making simple USB screenshots so you might have the Trigger menu showing so to show us Holdoff or a Decode menu.Blue Print button is just a useful shortcut to save to USB.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 04, 2019, 06:20:59 pm
content: An update:There are more details ragarding to issue.AB_lines_A_char_00.png - master transmits a single char 'A', there's no reply from the slave.AB_lines_A_char_with_reply.png - added a delimeter, so we have a reply. (distorted)AB_not_distroted.png - not distorted reply.sometimes the slave just a sweatheart...

author: tautech
author_rank: Super Contributor
timestamp: June 04, 2019, 08:22:37 pm
content: What is Ch 3 and how does its 140V p-p signal correlate to the data bus ?

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 05, 2019, 06:08:59 am
content: Quote from: tautech on June 04, 2019, 08:22:37 pmCH3 hangs on driver enable signal.In fact, there is not more than usual TTL level there. I just forgot to set the probe to x10 physically.Anyway it doesn't affect the timing.An update:the first one is ok;the second one is distorted;It's seen an unstable timing of slaves'sdriver enablesignal. So-calledfloating timing.The point is, the both are completed devices (serial production), and we can do nothing with timing. Both manufactures sweared that nobody before was complaining on such misbehaving.BR

author: tautech
author_rank: Super Contributor
timestamp: June 05, 2019, 07:32:40 am
content: Quote from: CiscERsang on June 05, 2019, 06:08:59 amI beg your pardon.TTL levels are 0-5V.Ch3 is displaying 20 something V !Now set the trigger to Ch3 and increase the timebase to carefully inspect the timing correlation between Ch3 and the data lines.My guess is Ch3 transition is affecting the data lines and that will be able to be seen with a much faster timebase as Ch1 and 2 spikes will trail the transition on Ch3.

author: mrpackethead
author_rank: Super Contributor
timestamp: June 05, 2019, 08:00:27 am
content: Tell the prof to talk to keysight, they are being super aggressive price wise for EDU, and will $/feature match the likes of Rigol and Siglent.

author: tautech
author_rank: Super Contributor
timestamp: June 05, 2019, 08:05:39 am
content: Quote from: mrpackethead on June 05, 2019, 08:00:27 amYeah right, like walking backward.

author: TurboTom
author_rank: Super Contributor
timestamp: June 05, 2019, 08:45:04 am
content: @CiscERsang -I`m not sure what`s your priority here, getting the 485 link operational or understanding how to use your new scope to analyze the problem. IMHO the communication problem has been spotted without even having to use a protocol decoder since it`s basically a bus collision. If the devices having the problem are out of series production, they should offer some way or the other to configure the bus protocol. See here for instance for some hints:https://automationforum.in/t/how-to-do-proper-port-settings-configuration-of-rs-485-modbus/1607To get familiar with the scope, there`s nothing that will replace a good amount of practicing, maybe with the help of an experienced user, and that`s where this forum can be quite helpful. To get comfortable with a modern DSO doesn't depend that much on the model or brand of the scope (as long as it provides the basic required functions) but rather on the approach to use it. The bus problem you encountered is for instance a very good opportunity to experiment with extended trigger option (pulse, maybe runt) and also to experiment with segmented memory and pass/fail recognition. A modern DSO provides so many functions that you've probably just skimmed the surface.Anyway, I'm sure you're on a good road to reach your goal and you'll finally master the encountered problems if you focus on them.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 05, 2019, 08:48:51 am
content: Quote from: tautech on June 05, 2019, 07:32:40 amDue to features of PCB we can't measure directly on corresponding IC pins. So it shows 20V something. Normally i was expecting a TTL level there.

author: tautech
author_rank: Super Contributor
timestamp: June 05, 2019, 09:52:45 am
content: Quote from: CiscERsang on June 05, 2019, 08:48:51 amOK good.So we have some elevated voltage for the CH3 TTL like the correct reference connection (ground) for Ch3 is unrelated to the data bus.The Ch3 step timing is as expected before the corrupt bus signals but nevertheless it looks mostly unrelated.Still I would take additional care that sufficient local bulkandfast decoupling capacitance is available for the bus devices so to be sure there isn't power rail blips causing the corrupted bus.Interesting hunt.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 05, 2019, 10:00:25 am
content: Quote from: TurboTom on June 05, 2019, 08:45:04 amBoth, as it's seen.Quote from: TurboTom on June 05, 2019, 08:45:04 amAs I wrote far above, both are set to9600, even, 1 stop bit. Also it's seen on oscillograms provided. Btw, I've already learned how to calculate that. In emergency case, just write me I'll show you how to do that.There are not any additional timing settings on both devices.Both devices (master & slave) are Germaninventions(world known brands, btw.). Now, we know who sits in german's support deportments and answers to support queries. At best it's a moonlighting student as a practice showed. When we started speaking about half-duplex issues, timing and delaying, they just disappeared from view. Still nobody competent and useful had spoken with us.Quote from: TurboTom on June 05, 2019, 08:45:04 amWe know. Do you have something useful for us?BR

author: Rerouter
author_rank: Super Contributor
timestamp: June 05, 2019, 10:17:14 am
content: Out of curiousity, does your RS485 bus use any termination, It should not be the cause of an issue, but if something is marginal it may be causing weird things like this. not with reflections of similar, more possibly the idle voltage level and correctly detecting things. as it seems like the current termination doesnt pull the idle level to the same voltage,for an example, try adding 120 ohms across A and B

author: Kean
author_rank: Unknown
timestamp: June 05, 2019, 10:18:47 am
content: Do you have bias resistors on the RS485 bus?https://www.google.com/search?q=rs485+bias+resistorsI find that they are more important than termination resistors for short cable runs and at slower baud rates, so the bus doesn't idle in an invalid state. It is somewhat hard to tell from what I've seen above if is this is a collision or biasing issue.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 05, 2019, 10:58:54 am
content: Quote from: Rerouter on June 05, 2019, 10:17:14 amHi there,A few weeks ago we played with termination. We tried all possible variants and that had not resolved the problem. Much water passed under the bridge (we leveled frames I mean), though. Moreover, the cable has so ridiculous length ~1m. Definetely we'll try to do that again.Anyway, thank you.Quote from: Kean on June 05, 2019, 10:18:47 amIf you compare initial oscillogramms with today's, you'll see a huge difference at leveling (before it wasn't leveled at all). Now, it much better than before. It's a result of implementaton of standard biasing. It's not a root issue, though, I think. An amplitude itself is still slightly different. As I wrote above we still can't measure power voltage of master's drive. The manufacturer sweared it's exactly 5.0V. The slave, for its part, has 5.0V, we measured that by themselves.Anyway, thank you.

author: Kean
author_rank: Unknown
timestamp: June 05, 2019, 11:04:34 am
content: OK, so it does seem like a collision. The master may be disabling its driver "too late", or the slave enabling the driver and transmitting "too early".Also, do you have a common power supply ground between the master and slave? Maybe connect them using a 100R 1W resistor if you think there might be a voltage difference.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 05, 2019, 11:31:43 am
content: Quote from: Kean on June 05, 2019, 11:04:34 amit was discussed at #36 and at related replies.Quote from: Kean on June 05, 2019, 11:04:34 amAn idea of this standard sounds e.g.half-duplex(A-B lines & common ground), not more. They must have separated power suplies at least related to TTL levels.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 05, 2019, 12:50:50 pm
content: @tautech,Quote from: tautech on June 05, 2019, 09:52:45 amas it's seen a rise edge (blue one) ofdrive enable signalcoincides with the beginning of corruption. Doesn't it?Quote from: tautech on June 05, 2019, 09:52:45 amI did some study on shematics...A capacitance... there's a smd tantalum capacitance in the nearest vicinity (power rail is not more 1.5 cm length). Btw, at the beginning, we tried to solder there an other smd tantalum 4.7 µF. No success...My guess is, at least it looks so, for some reasons:mostly, the slave's, let's say, itsbrainprocesses a query too fast. So, it causes a distortion at the beginning of reply (it's clearly seen on the oscillograms).however, sometimes the slave processes a query as it should be. Please note, it's seen at #57, it left an entire byte behind (I mean anidlespace), then began responding.Of course, as a cure I would try a timing setting. Unfortunately there's no any timing setting available for the slave or master.Why such good event occurs not constantly. The story has no records.BR

author: tv84
author_rank: Super Contributor
timestamp: June 05, 2019, 02:27:06 pm
content: CiscERsang,I bet the Prof only asked you to buy the Siglent not to procure the solution in EEVBLOG to your problems.I think you should try harder to solve the problem on your own now that you have clarified the scope's behavior. That's the beauty of the thing!

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 05, 2019, 02:40:21 pm
content: Quote from: tv84 on June 05, 2019, 02:27:06 pmanother one... If you have something useful to say, you are welcome. If you just want to. let me say, don't interfere with us please.

author: TurboTom
author_rank: Super Contributor
timestamp: June 05, 2019, 04:44:09 pm
content: Quote from: CiscERsang on June 05, 2019, 10:00:25 amThank you, I'm out of this and you've got the honor of being the first EEVBLOG member on my "ignore" list.All the best,Thomas

author: tautech
author_rank: Super Contributor
timestamp: June 05, 2019, 10:46:26 pm
content: Quote from: CiscERsang on June 05, 2019, 12:50:50 pmImage embedded for context.Observations and questions to consider.Where you mark the start of corruption might also seem like a jump to slave bus levels as signals from the master Ch1 increases in amplitude while Ch2 decreases. Confusing.Ch3, the TTL (something) is apparently negative and positive going....also confusing.Is Ch3 from the master or slave side of the bus ?I'm out of ideas of where to look next other than replicate the devices and bus traffic on another custom PCB so you can prove the problem lies with the master, slave, code or supply rails or some undiscovered combination of them.As for advice on possible packet collisions, this is out of my experience so I advise you to listen to contributions made from other members.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 06, 2019, 07:40:33 am
content: Quote from: tautech on June 05, 2019, 10:46:26 pmYes, this looks as an untimely jump, because it's already slave's bus levels (so-calledmarkstate). I wrote about this somewhere above. We managed to level both buses frames (biasing). However, a difference at amplitude still persists.Quote from: tautech on June 05, 2019, 10:46:26 pmCh3 hangs on slave's signal line calleddriver enable. So to speak, between brain and driver.Quote from: tautech on June 05, 2019, 10:46:26 pmWe are out of ideas too (except timing), and not only we, judging on yesterday's replies fromsomeother people which were out of ideas long before us and had started writing beside the point.Anyway, thank you that didn't leave us

author: tautech
author_rank: Super Contributor
timestamp: June 06, 2019, 07:52:43 am
content: Quote from: CiscERsang on June 06, 2019, 07:40:33 amLet's investigate this more.So for that 20 odd volt p-p 'driver enable', how is that electrically related to the slave ?Its enable signal tells the slave to transmit right ?How is that 20V p-p signal interfaced with the slave that transmits at a much lower level ?What is the max rated input into the slave's enable pin ?Can you share with us the device type or a link to the slaves datasheet ?

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 06, 2019, 07:54:13 am
content: Quote from: tautech on June 06, 2019, 07:52:43 amThis is OEM PCBs. Mostly comprises smd 1204 size and less. It's quite tough to draw that. I had to make a sketch. Please see attachment.Quote from: tautech on June 06, 2019, 07:52:43 amexactly!Quote from: tautech on June 06, 2019, 07:52:43 amIt's hard to say. I need more time to trace that PCB based on 1204 smd components and PCB also has three or more layers, I think.Quote from: tautech on June 06, 2019, 07:52:43 amPlease see attachment. Note, CH3 hung on not directly on DE (drive enable) pin. I need to perform some work to hang on that directly (solder a wire).

author: tautech
author_rank: Super Contributor
timestamp: June 06, 2019, 09:16:39 am
content: Quote from: CiscERsang on June 06, 2019, 07:54:13 amOK please check the levels directly into the DE pin.If we study the screenshot again:We can see above Ch3 goes quite negative and beyond the absolute max rating of -0.5V.For those playing along, here's the datasheet:https://datasheets.maximintegrated.com/en/ds/MAX1487-MAX491.pdf

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 06, 2019, 09:27:07 am
content: Quote from: tautech on June 06, 2019, 09:16:39 amPlease point me out a place where Ch3 begins going negative. I can't see that.As soon as I make proper measuremnts I will make an update.

author: tautech
author_rank: Super Contributor
timestamp: June 06, 2019, 09:35:52 am
content: Quote from: CiscERsang on June 06, 2019, 09:27:07 amSee the Ch3 marker at the left edge of the screenshot, any part of the waveform when DC input coupled below the marker is a negative voltage.Yes sorry, I should have been more clear, it's already negative and going positive at the start of the bus corruption.Still, where you have measured this DE value it is clearly negative and beyond the IC's acceptable ratings.You need to check it again on the IC DE pin.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 06, 2019, 09:37:59 am
content: Quote from: tautech on June 06, 2019, 09:35:52 amI've got that.A couple of days ago I wanted to ask you what's function of those markers on the left side.

author: tautech
author_rank: Super Contributor
timestamp: June 06, 2019, 10:04:33 am
content: Quote from: CiscERsang on June 06, 2019, 09:37:59 amSimply they're the 0V (no signal) channel markers and their position in volts (relative to mid display 0V) is also on the channel tab below the V/div setting. If you place them off the display their shape changes to a pointer that indicates the channel is positioned off the display.Any channel can be re-positioned to the middle of the display (0V) with just a press of the active channels vertical position encoder.All of the encoders have additional press functions that are written in small text below each encoder.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 06, 2019, 08:48:40 pm
content: @tautech,as you asked...An update:please refer to homemade el.diagram where coloured points are measurement points. Also please refer to file names they are also meaningful.slave's el.diagram;common view not readable reply;common view readable reply;zoomed not readable reply;zoomed readable reply;dancing timing sample 00dancing timing sample 01An observation:There have been done a few dozen of queries. I wouldn't say thatdancing timinghad affected significantly tounreadable/readable.Unlikedancing timing,corrupted start bit's topwas always affecting tounreadable/readable.BRI had to figure out a place ofstart bit. Since I'm already a huge expert on decoding differencial buses.It was quite easy to figure out a place of that bit. I'm halfway, a sudden thought... It's UART's frame, I can force Siglent to do that.Siglent's decoding looks nice.Anyway, I fiinished that by myself.

author: Electro Fan
author_rank: Super Contributor
timestamp: June 07, 2019, 06:03:04 am
content: A couple other ideas:1. Take a short break from your R485 project and probe and decode something easy like R232 on a PC, or maybe I2C with Arduinos just to confirm you are fully familiar with Siglent decoding basics. Either you will confirm that everything is operating just the way you think or you will discover something new about Siglent probing and decoding - which might or might not be applicable to your RS485 project.2. Once you reconfirm your Siglent decoding bearings then try a new different RS485 DUT setup - find a different set of hardware to test. If by chance you can decode the new RS485 DUT setup then we know there is some obscure problem with your current hw DUT or the general setup, but at least you will have gained some confidence in your Siglent RS485 decoding skills.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 07, 2019, 06:10:07 am
content: Quote from: Electro Fan on June 07, 2019, 06:03:04 amDear Electro Fan,we are not experiencing any problem with decoding buses. We are ok, Siglent is ok.you need to read posts a bit carefully. Prefereable from the beginning.Sorry, no offence, mate

author: Electro Fan
author_rank: Super Contributor
timestamp: June 07, 2019, 06:14:42 am
content: I’ve read your entire thread, mate.

author: Electro Fan
author_rank: Super Contributor
timestamp: June 07, 2019, 06:18:53 am
content: If you are ok, and your Siglent decoding skills are ok, then prove it by successfully decoding another RS485 DUT setup. After you do that you can look for differences in the two setups with substitutions, test by test.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 07, 2019, 06:29:37 am
content: We don't decode bus frames by themselves (senselessly, I've done that once, though). It does special proven equipment (so-called Master). It works fine with various other RS485 devices (slaves).BR

author: Electro Fan
author_rank: Super Contributor
timestamp: June 07, 2019, 07:48:21 am
content: Have you tried another Master?

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 07, 2019, 07:56:13 am
content: Quote from: Electro Fan on June 07, 2019, 07:48:21 amit was first what we had done. This is very specifical issue. This is question of adaptation, so to speak.

author: Electro Fan
author_rank: Super Contributor
timestamp: June 07, 2019, 08:01:55 am
content: Quote from: CiscERsang on June 07, 2019, 07:56:13 amAnd that would meana) you have tried only one Master so farorb) the first thing you did to figure out the problem was to try a second MasterWhich is it: a or b ?

author: tautech
author_rank: Super Contributor
timestamp: June 07, 2019, 08:13:05 am
content: Can’t help much as I’m away but I want you to reset the V/div back to Coarse for each channel by pressing the V/div encoder.Then enter Measure and select a V p-p for each channel in use.These two things will help to see amplitude at just a glance and also keep waveform amplitude in a better relationship to each other.Then you can overlay waveforms for better visibility of timing relationships.I’m still watching if/when I can.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 07, 2019, 08:18:20 am
content: Quote from: Electro Fan on June 07, 2019, 08:01:55 amb)In other words, both Masters work fine with various other slaves and work unstable with only one type of equipment which is described here.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 07, 2019, 08:19:25 am
content: Quote from: tautech on June 07, 2019, 08:13:05 amok, tautech.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 08, 2019, 04:54:04 am
content: Quote from: tautech on June 07, 2019, 08:13:05 am

author: tautech
author_rank: Super Contributor
timestamp: June 08, 2019, 05:20:47 am
content: Nice.You do have enough vertical realestate to show both waveforms at the same V/div setting as now we’re not so interested in amplitude more so timing relationship between EN and the start of the packet.You can speed things up more with the timebase control but to keep things in better perspective this is where I’d use the dual (Zoom) timebase to examine the glitch in fine detail. You can slow the main timebase down heaps if you still have the trigger catching the EN and speed up in Zoom to see just the glitch.One more thing I’m not understanding is the size of your screenshots as they should be only ~50kb max when got with the Print button to USB.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 08, 2019, 06:12:42 am
content: Quote from: tautech on June 08, 2019, 05:20:47 amOne thing confuses me: We have ~6 V amplitude at both input terminals. In datasheet is written max.ratings -0.5...5.0V at these inputs. Is this an amplitude mentioned? Should we consider that?Or?Quote from: tautech on June 08, 2019, 05:20:47 amThat's web-serverproduction, see our current network config description above at #34. We don't use USB function at all.Btw, while scope usage I noticed some things (IMHO), that could be implemented in the next FW issues. That's not so hard to do (hardware independent stuff).

author: tautech
author_rank: Super Contributor
timestamp: June 08, 2019, 06:31:51 am
content: Hard to get quotes correct on an iPad so respective repliesThe IC output levels are related to their VCC/VDD plus DSO measurements are indicative NOT accurate like a DMM. Another thing to consider is the displayed info that the measurements are taken from.Slow the timebase and have more waveforms displayed and measurements will be more precise.Ok webserver, I did wonder, anyway great you’re using it here.Any improvement suggestions post them here, the 4ch X-E thread or PM me.Probably the X-E thread so to get others discussing too and/or support for them.

author: Kean
author_rank: Unknown
timestamp: June 08, 2019, 02:06:37 pm
content: Quote from: CiscERsang on June 08, 2019, 06:12:42 amYes, this is because whoever designed this circuit took shortcuts leading to a poor design. They relied on the 49k resistors to limit current from the +/-10V MAX232 outputs into the 5V CMOS MAX485 driver chip inputs. The internal ESD protection diodes try to clamp the weaker signal, but by doing this they've potentially compromised signal integrity.It is interesting that they used a schottky diode on the driver enable signal and not the driver input. I was going to suggest you may have missed that on your reverse engineered schematic, but you can see the difference this makes in your last captures. Both signals exceed the 5V Vcc upper bound of the MAX485 chip, but the DI signal also possibly exceeds the lower bound by going below -0.5V.I would make two suggestions to try narrow the problem down, but they may take a little effort:1. Remove the 49k resistors, and insert a TTL or CMOS inverter from the signal on the other side of the MAX232 into the MAX485 inputs. This should give uncompromised waveforms, and help you determine if this part of the circuit (lazy level shifting) is causing your problems.2. Monitor both the DI signal into the MAX485, and the RO signal on the matching driver in the slave. Do this in the same capture and compare them to see if the data is being corrupted. You may also need to do the reverse for the response comparing the slave DI pin to the master RO pin. Trigger off the respective DE pin. You said the cable between the master and slave is only 1m, so I'm guessing this shouldn't be hard - but be aware the scope grounds will directly connect the master & slave grounds.If the master and slave use different UART master clocks & dividers then their baud rates could be right near the edge of tolerance (e.g. opposite ends of tolerance) and thus any compromised start bits could cause loss of communications. Somewhat unlikely at a slow baud rate like 9600, but who knows what you may find when other short cuts have clearly been taken. Much more likely there is bit corruption at the leading or trailing edges of the data packets due to poor inter-packet timing control. You have already shown that the timing control of the DE pin on the master is inconsistent.Also what you haven't shown is how the MAX485 RO pin is handled. If it also goes through the MAX232 (for inverting) is may also be compromising the receive data waveforms as seen by the UARTs.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 08, 2019, 03:47:06 pm
content: Quote from: Kean on June 08, 2019, 02:06:37 pma small remark,TTL/CMOS <---> MAX232 <---> RS232 <---> MAX485,because MAX232 is TTL/CMOS -->RS232 converter.Quote from: Kean on June 08, 2019, 02:06:37 pmNo, that's not a mistake.Quote from: Kean on June 08, 2019, 02:06:37 pmplease find el.diagram update.All other things at processing phase.

author: tautech
author_rank: Super Contributor
timestamp: June 10, 2019, 10:35:39 pm
content: Spotted some tips that might be useful to link here:https://www.eevblog.com/forum/beginners/rs-485-protection/

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 24, 2019, 12:09:42 pm
content: @tautech,could you testdecodingin a way as it's shown. It seems it doesn't know 'question mark'. The decoding conditions are ok. A message sounds likeWHY?;If it will be confirmed by your test, please put it in my list. You know which one.One more question, a timebase 200us next 500us. There's nothing between them. Is it a standard, or?BR

author: tinhead
author_rank: Super Contributor
timestamp: June 24, 2019, 07:34:47 pm
content: Quote from: CiscERsang on June 24, 2019, 12:09:42 pmi would not call standard but common, one can find e.g. 1:2:5 or 2:4:8 based scales (there are others as well, like 1:2.5:5). Some manufacturers provides as well fine timebase adjustment (not that one need every day 127ns/DIV, but yeah, having 2:4:8 based gear with fine adj allows me to adjust my screen similar to other gear, which is 1:2:5 based).

author: tautech
author_rank: Super Contributor
timestamp: June 24, 2019, 10:45:02 pm
content: Quote from: CiscERsang on June 24, 2019, 12:09:42 pmSorry I only have STB-3 with UART to check with so cannot check that '?' is recognized correctly.Maybe RS485 has a different character set, I do not know.QuoteThere is always another way to get the info you seek, sure in CRO days we had a Fine timebase but today we have the more useful Zoom mode that especially with Decode allows us to keep a better track of where the byte of interest is in relation to the entire packet or data string.I encourage you to get competent with Zoom and learn how to examine each byte in detail using the Horizontal position control.Generally it's best to select 50ms/div (just below auto Roll mode) for full memory depth and to get as much info on the display before selecting Zoom and then use the zoomed timebase and H Pos to get the info you seek on the zoomed window.The blue V trigger position indicator indicates where you are in both un-zoomed and zoomed windows.Remember also that all of the encoders have a dual use, rotate for movement/adjustment and press for reset to 0, coarse adjustment, 50% etc.

author: CiscERsang
author_rank: Regular Contributor
timestamp: June 25, 2019, 04:13:47 am
content: Quote from: tautech on June 24, 2019, 10:45:02 pmI can read/write novels. Since the receive memory = 4096 byte, the transmit memory = 1023 bytes;Quote from: tautech on June 24, 2019, 10:45:02 pmSince this signal was taken from MAX232 output leads, that means it'spure UARTsignal. Not differential one.So, please put it in my list of wishes.Quote from: tautech on June 24, 2019, 10:45:02 pmI used Zoom sometimes. However, a question had arisen, why there's so big time gap between 200us and 500us. So, I asked you.thank you.

author: tinhead
author_rank: Super Contributor
timestamp: June 25, 2019, 09:11:40 am
content: Quote from: CiscERsang on June 25, 2019, 04:13:47 am#103it is 1:2:5 based scale, nothing else