Hacking the Rigol DHO800/900 Scope

[iMo]

Sure they will be not as I wrote finally above..

[iMo]

Re DHO-824 - do you see "dBm/dBV" in the FFT menu?
I can see that in the user guide, but not here (v 00.01.04.XX) - I can see dBV only..
Also where to get the XX? I upgraded from 1.03 in January, but not sure what was the XX..

[mawyatt]

Rather than sampling the DTFT spectrum of the windowed signal using a DFT, one could use a CZT instead. This would enable the DTFT spectrum to be sampled non-uniformly (e.g. on a logarithmic scale, or even an arbitrary scale). However, the spectrum analysis filter still retains the same shape and bandwidth at each frequency point.

The CZT seems to be lost in time, altho I think someone mentioned Keysight was using it in one of their latest instruments. Back in ~1982 we developed a hand-held (well text book size) Real Time Spectrum Analyzer based upon the CZT, it utilized custom long CCDs for the complex convolution which was performed in the discrete time continuous amplitude (DTCA) domain. It took the computing power of a 1/3 of a Cray One at the time to do the same computations with an FFT!!

Anyway, these new 12bit entry level DSOs seem to be generating some interest in low frequency noise analysis/characterization. Sure hope iMo is successful in getting the noise spectral density plots as shown, that would be really impressive indeed!!

Best

[mawyatt]

Aaah, ok, I see..

..and to beat the Siglent - could the freq be in log10(freq)? 
Such we see the bins "evenly" (sort of, they will be not, but such they are visible) distributed through decades?
Like you have 10div each 100secs (example only) so the lowest frequency in the fft could be in milliHertz (or lower) and the highest in XXkHz - that is many decades (afaik the FFT is always max 1Mpts, so 5-6)..
A typical graph people want see after N averagings:

This should be great if folks can create graphs like this with these entry level DSOs!!

Maybe we should change the title wrt these noise analysis/characterization uses with these DSOs and not refer only to Siglent.

https://www.eevblog.com/forum/testgear/siglent-fft-uses-for-low-frequency-noise-analysis-and-investigation/

Overall having all the knowledgeable "low noise DSO folks" concentrated in one thread should prove useful for everyone with whatever brands they have, hopefully not creating the usual DSO wars!!

Best   

[iMo]

Creating such a functionality which performs well is not easy and usually requires a lot of testing and practical measurements.

I doubt it could be done effectively while communicating with the vendors only (sw and/or hw). Ideally there is a "versatility built in" - allowing the "creating your own functionality upon the existing o'scope ecosystem", like a built-in script language or something like that. We do not have that yet, so the only feasible option I see is to use the scopes as digitizers only and do the math and graphs off line (like in python etc).

On the other hand you do not need an 2Gs/s with 100MB of memory oscilloscope to mess with noise measurements of this nature, almost anything will do as well..

[crysti]

What is your opinion: is it possible to extend the bandwidth by replacing the amplifier in the front-end, or even by replacing the entire front-end with one matched to 50 Ω, similar to the approach I have seen in another design built on a custom PCB, soldered directly on top of the original front-end?

[norbert.kiszka]

What is your opinion: is it possible to extend the bandwidth by replacing the amplifier in the front-end, or even by replacing the entire front-end with one matched to 50 Ω, similar to the approach I have seen in another design built on a custom PCB, soldered directly on top of the original front-end?

Front-end in this series (DHO800&DHO900) already has bandwidth above 1 GHz, so why You want to replace it? 50 Ω termination can be added very easily both externally and internally. In the second case, You can use four 49.9 Ω 0.1% 0.25 W resistors and solder them in serial-parallel to the joints of the BNC socket on the PCB. I did it in my scope in one channel along with the increased bandwidth by removing filters.

[abobbie]

Thanks for all your work on this Norbert!

I'm looking at the DHO804 as a first scope and they're on sale right now, before I go through with this I just want to confirm a few things given the quotes below;

with your firmware / patreon purchase
1. the 70Mhz can be upgraded all the way to 270MHz? (or 250 safely)
2. the logos that appear on the screen during boot and on the interfaces can be changed or customized? is that just by you or can we modify our own logos / images?
3. does no. 2 include font modifications on our end?
4. it's possible to increase the memory depth of the scope beyond the 25/50 points given the physical hardware present on it?

   

   

   and DHO8xx can be hacked to have 200 or even 250 MHz.
   

   About 270 MHz IIRC, if we define bandwidth by the -3db drop -- that's determined by the analog input filter.

   Of course it (or any of the 8xx or 9xx scopes) is usable at these frequencies in single-channel mode only, <...>more realistically, up to 1/3. This is determined by the signal reconstruction algorithm, which sucks in these scopes (the Siglent's is better, for comparison).
   

   

   that font that I used for the boot logo for the scope, was made by Airbus and they used it on the screens that pilots use in flight decks to make You safer - even by making their own font (sadly they made some simple mistakes around redundancy in FBW computers...).

   Even with the source code, Android is more like a toy, than operating system. If Android is based around (modified) Linux kernel and it's safer and (as they say...) and more efficient than regular Linux/GNU, then why most expensive data centers (including Google which maintains Android) use "regular" Linux instead?


   

There's now three different ones to choose from...

   

   

   Some or all of those "new" decoders may not work properly or at all - looks like there is no full coverage in code, like a max and min threshold levels that You can set - in this case there is a input, so You can chose whatever You like, as long it's black (I mean 0 V). In such case, I need to add or change some code - likely stolen from a DHO4000.

   Believe or not, there is a code for even more decoders and triggers, but that will not be easy to make them work - more or less.

   Anyway, couple days ago I "succeed" to put this into 2 GSa/s, but there were random spikes added to the waveform, which were shorter than the time of one sample. Obviously those spikes comes from the app, not from the hardware. Lately I found some fragments that probably can be changed to get rid of those spikes.

   But first things first - now Im working with the user selectable bandwidth limits (filters in AFE). Currently 20, 70, 100, 125 are working (maybe also 200 - I remember it was working and now it's not...), but that's kinda not much options - at least for me. Something around 250 and 400 would be nice - in that case I will be able to do auto bandwidth option (all options for each channel separately) - lower sample rate will change bandwidth to lower and inversely. I think at least 200 and 250 are possible (DHO4000 has 250 setting - but I don't want to copy huge amounts of code - at least for now).

   BTW. I wonder how many users would wan't to have 250 Mpts memory depth. Theoretically it can be done, since 4 Gb chip gives space for 256 M pts. Currently I can easily change 125 M to 128 M (or maybe 2 ^ 27), but I didn't want to fix one Rigol bug just for those 3 Mpts extra - maybe I will one day - 128 M can be divided by 2 many times and that's pretty useful. Hacking for the 250 M pts (or 256 M) will take some time without any warranty to success (FPGA firmware which I didn't touch yet).
   

[norbert.kiszka]

1. the 70Mhz can be upgraded all the way to 270MHz? (or 250 safely)

In my mod I removed all Rigol licensing system - which BTW, enables some options from DHO4000 (Rigol used same code to built this firmware). So by default You have as much bandwidth as the hardware will give.

Also, You can select manually (in the channel settings - separately for each channel) AFE filters: full (usually >250 MHz unless You removed or changed LC filters between AFE and ADC), 400 MHz, 125 MHz, 100 MHz and 70 MHz.

2. the logos that appear on the screen during boot and on the interfaces can be changed or customized? is that just by you or can we modify our own logos / images?

If You unpack zip package from my mod in version 0.3 (currently only as a enterprise edition, later also as a home edition after I'll finish fixing bugs) You should have folder named custom_bootsplash. Installation script is looking for a file named image.bmp in this folder. If it exists, it's used as a system bootsplash.

In previous versions (currently v0.2.1 normal edition), script was looking for a file named custom_image1.bmp in the same directory as the installation script.

3. does no. 2 include font modifications on our end?

You can put whatever You like as a bootsplash, like a full screen image with a text only (with any font You like) or some photo or anything else.

4. it's possible to increase the memory depth of the scope beyond the 25/50 points given the physical hardware present on it?

Hardware theoretically should allow to use 268 Mpts, because FPGA DDR chip is 4 Gb (single point takes 16 bit). Likely about half of it is reserved by the FPGA firmware (AFG, LA, screen waveform points, etc), so practical (tested) limit is 134 M. Currently my mod allows You to select up to 125 M. If You are going to use more than 62.5 M in total, I strongly advice to use single shot button instead of stop button, because if You will use stop in such settings and after that You will change time base (still in stop mode instead of single shot), waveform can be disrupted.

Because of the lack of the original source code, I wasn't able to determine why this is happening. I'm planning to do a workaround by adding code to make a single shot when somebody will use stop with such memory setting.

More details about changes that I made, You can find in the changelog for all versions from the beginning.

[dzebrys]

What is your opinion: is it possible to extend the bandwidth by replacing the amplifier in the front-end, or even by replacing the entire front-end with one matched to 50 Ω, similar to the approach I have seen in another design built on a custom PCB, soldered directly on top of the original front-end?

you can check mso5k thread where similar mod is evaluated by Neekeetos
https://www.eevblog.com/forum/testgear/hacking-the-rigol-mso5000-series-oscilloscopes/msg5175111/#msg5175111

[gastonmariano@gmail.com]

Hello to All
I am strugling with almost bricker dho804, I want to make afresh starts, I saw reference to a clean SD CARD Image, but those link are dead. and the working one is not clean is with the hack, do anyone can share a link to any fresh sd card image?
thanks and regards

[norbert.kiszka]

Hello to All
I am strugling with almost bricker dho804, I want to make afresh starts, I saw reference to a clean SD CARD Image, but those link are dead. and the working one is not clean is with the hack, do anyone can share a link to any fresh sd card image?
thanks and regards

Look at the very beginning of this thread.

[gastonmariano@gmail.com]

I saw one that is already hacked, I need a clean one to start over. now is working but sometime I need to restart 4 times until it boot, I will check again, maybe is there and I did not see it.
thanks

[gastonmariano@gmail.com]

still did find it in first page. so if anyone have it, please let me know

[norbert.kiszka]

Laziness become very popular these days.

[mrisco]

still did find it in first page. so if anyone have it, please let me know

Just use the image in the first page and copy your original /Rigol/data folder.

[gastonmariano@gmail.com]

I did that already. and is king of working, but I have to try a few times and remove power to make it boot. may be a problem witn sd card and not image itself. thanks

[norbert.kiszka]

I did that already. and is king of working, but I have to try a few times and remove power to make it boot. may be a problem witn sd card and not image itself. thanks

May I ask which SD card brand You are using?

Did You try to listen UART output?

[norbert.kiszka]

I removed insignificant zeros and increased displayed precision almost in the whole app. How does it look?

If there will be no complaints, I will make final changes and release will be available likely in the next ~24h (as a free update if somebody purchased it earlier).

[gastonmariano@gmail.com]

I am using the OEM one that came installed,  lexar 32gb

[norbert.kiszka]

I am using the OEM one that came installed,  lexar 32gb

Originally used U-Boot somehow can't work on other SD cards than Lexar - that's why I was asking for the brand.

To be honest, I guess Your laziness didn't allow You to answer about UART, which I mentioned earlier.

BTW. After I will release 0.3.2 (or whatever version number it will be) likely I will prepare newer and modified (because of drivers and other things) Android - probably 9.x or 10.x, because of much less bugs, much better performance (faster boot and more wfm/s), possibility to install newer apps and possibility to run it from other SD card brand. But only if there will be enough support for it on my Patreon. Otherwise, I will be working with other oscilloscopes.

[AndyBig]

Originally used U-Boot somehow can't work on other SD cards than Lexar - that's why I was asking for the brand.

The oscilloscope boots and works fine with SD cards other than Lexar.

[norbert.kiszka]

Originally used U-Boot somehow can't work on other SD cards than Lexar - that's why I was asking for the brand.

The oscilloscope boots and works fine with SD cards other than Lexar.

Maybe Your scope, but not mine DHO924S. However my "Orange Rigol" uses also U-Boot with similar version and it can boot from any card.

[mrisco]

The oscilloscope boots and works fine with SD cards other than Lexar.

Mine too, tested with two other brands. Just make sure the new card has enough space for the complete image.

[Fungus]

I've booted mine of cheapo no-brand SD cards from Aliexpress.