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| Sniffing the Rigol's internal I2C bus |
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| eV1Te:
Too bad the codes have not been sorted out for the MSO yet. By the way how good is the decoding function in the MSO? I was debugging RS232 from a GPS today on my DS1074Z-S, and the decoding function is really terrible, almost unusable. It only decodes the waveform on the screen at the moment (not outside the screen), so if you scroll (move horizontal) past the beginning of the transmission it losses its sync and interprets the first rising edge that you can see on the screen as the start-bit which scrambles the entire message. If you "zoom-out" then it can not decode any data at all because the it only decodes whats in the screen buffer (it does not use the large memory capability of the scope), and this data aliases very early on. Hence it is impossible to to view more than the first ca. 15 bytes/characters of a transmission. If you are lucky and there are gaps between each byte , then you can manually can set the edge of the screen to be in one of the gaps, but if you have a continuous string of bytes then you are out of luck (unless you are lucky and happen to have the first bit just at the left part of the screen). I also tried using the event table or single capturing a longer sequence without any luck. Triggering of a character in the middle of the transmission doesn't work either because the decoder scrambles the message anyway (since it can not see the start of the message) even if the trigger stopped at the correct spot. I watched this video from Rigol demonstrating the decoding function on a DS4000 scope, there they specifically say that you can zoom out and use the event table if your message is long and does not fit on the screen. Apparently the DS1000Z series of scopes has seriously downgraded decoding function and is not comparable to their more expensive scopes. |
| diyaudio:
--- Quote from: eV1Te on November 04, 2014, 09:49:34 pm --- I was debugging RS232 from a GPS today on my DS1074Z-S, and the decoding function is really terrible, almost unusable. --- End quote --- I decoded data from a ublox GPS, the $GPRMC USART data was decoded pretty well. Sometimes you need to double check your scope setup it happended a few times where i blamed the decoders. I own a DS2072A using the hacked firmware. |
| alank2:
I think part of getting the decoders to work well is getting the trigger setup properly and also understanding that by default you aren't doing a single capture and review, but by default the scope is trying to trigger as many times as possible so it can provide a gradient display. I think the result would be better if you (1) setup the trigger to trigger on the even you want to, (2) set the timebase so that you can capture all of the event on one screen, (3) set the trigger mode to normal not auto, and (4) once you have captured then go to stop mode so no more capturing can occur. Whether or not the decoding stays aligned when you expand the signal and start moving through it I am not certain. I've had it act like if part of the signal goes off the screen it lost its way and it seems like I've had it handle that properly at other times so I don't know if I was still running or stopped and reviewing the waveform. edit : I don't see such a great value in the decoders. I'll use them if convenient, but I much rather use a Saleae Logic or LogicPort. |
| eV1Te:
--- Quote from: diyaudio on November 04, 2014, 09:59:22 pm --- --- Quote from: eV1Te on November 04, 2014, 09:49:34 pm --- I was debugging RS232 from a GPS today on my DS1074Z-S, and the decoding function is really terrible, almost unusable. --- End quote --- I decoded data from a ublox GPS, the $GPRMC USART data was decoded pretty well. Sometimes you need to double check your scope setup it happended a few times where i blamed the decoders. I own a DS2072A using the hacked firmware. --- End quote --- I am willing to bet that the DS2000 series scopes have a much better debugger in that case. No doubt the DS1000Z only uses the screen buffer for debugging, and that's probably around 1k points or less. Doesn't the DS2000 have 2 FPGAs and the DS1000Z only 1? The debugger works fine for short transmissions or for the beginning of a transmission, but fails completely for longer messages or when triggering in the middle of a message. Maybe this will convince me that I "have" to buy a real logic analyzer as an early Christmas gift for my self ;) |
| msraya:
Well, yesterday a colleague and I were debugging a FPGA design using I2C serial bus port. I already knew that the I2C decodification does not work and indeed It was not showing anything in I2C testing close to reality. Also, as we were doing scroll sideways in the capture zoom, the oscilloscope was completely blocked and We had to restart it. However, the decoding of serial bus was successful (there was enough space between characters, it was not a data stream) For the purist this is a serious error and the manufacturers have lied about decoding specifications. However rethinking it, this equipment can not be compared with the more powerful DS2000 series since it only has a single FPGA for decoding and display. With this in mind it is questionable the usefulness of decoding and I would not pay 188 euros for it. In any case, the oscilloscope worked well comparable to Agilent 6000 Series we have as logic analyzer. We do not use decoding. The scroll is somewhat slow, but it is still usable. I can not test the SPI bus decoding, but it seems that for others users it decodes correctly. If I had known before buy this issue, I would have perhaps opted to buy a MSO2000 series. However for the price and the features I'm happy. I have made also testing with the generator and FFT and it is working properly. It's a shame that the Ultravision software made by user marmad does not support the model MSO1000Z. I have contacted the author but I have not gotten any response yet. Regards Manuel |
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