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SainSmart DDS120 & DDS140 USB Oscilloscope

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merbanan:
Ok, I got it all explained now. At 48MHz ("50Ms") sample rate the scope gets one frame of 1024 samples. That should be enough to capture most periodic signals. As you/others wrote before the scope is blind most of the time. The waveform update rate on this scope is low.

But the hardware can deliver more then it does with the vendor software/firmware. For example the fx2lafw firmware is able to sample at a rate of 24MHz with a logic analyzer with 8 pins. So it should be possible to get one channel with a continuous sample rate of 24MHz and 12MHz with two channels. So I just need a firmware implementing that. And yesterday I was able to get the custom Hantek 6022 firmware working. So now I need to get the gain stage working and get proper samples out of the scope.

doctormord:
Nice, please check your private messages.  :-DMM

andrej:
Hi!

I  wanted to buy DDS140, and did a little research on the product. In that process I came across this thread. I haven't read it thoroghly, but I see that on many places, one of the major problems with DDS140 is triggering. I also came across this product on ebay http://www.ebay.com/itm/SainSmart-Hardware-Trigger-Module-for-DDS-140-Oscilloscope-/301789209154?hash=item464409e242:g:ILgAAOSwd0BVp1yg
Does this make things better? Has anyone tried it?

I am aware of the limitations of this kind of product, but I am going to buy either hantek 6022B or DDS140,or DDS 120. I am aware of tehnical specifications (by wich dds140 is the best from these 3 Products), but what do you think would be a better choice, when you consider downsides discovered in this thread, and when you consider available software?

P.s. Sorry for my bad english

bianchifan:

--- Quote from: andrej on March 28, 2016, 07:56:58 pm ---I am aware of the limitations of this kind of product, but I am going to buy either hantek 6022B or DDS140,or DDS 120. I am aware of tehnical specifications (by wich dds140 is the best from these 3 Products)

--- End quote ---
A couple of months ago I thought exactly the same direction  8)
Some words to the trigger.
Sadly it's not very stable as I'm used in former times with my old analog Hameg.
Nevertheless it's usable for timebase > 1 us, on shorter base the signal is runnin' thru..
CH2 can only be triggered together with CH1, a lonely CH2 is running to Mars.
I do not think, the external trigger will change anything, it's just another base.
I guess that the module s only an enclosure for the two lines.
Have a look on my oics above, they are connected to pins 1 and 4 on the bottom row.
You can stick to with a Dupont jumper.

Sometimes CH2 is very noisy, until now I couldn't evaluate the reasons.

The greatest disadvantages IMHO are the input dividers.. :-- :--
The max. possible positive voltage is ~6V, the max neg. voltage (DC) sometimes 1.6 V, sometimes 3.6 V, max possible neg. voltage AC ~5V.

Result: At logic level you need an external 1/10 divider.  :palm:

My reason for buying were the 200MSa, 'cause I wanted a "real" 20 MHz scope.
If you can live with an absolutely shitty software you can work with.

merbanan:
Ok, I have now sent a pull request for support in Sigrok. I added a new firmware based on the Hantek 6022BE firmware. Coupling support is missing in the firmware but other then that it should be feature complete. To maybe be added is the possibility to change the frequency of the 1kHz pulse and to add a few more sampling frequencies.

What more is missing is a good oscilloscope application that can use the driver. But pulseview should be quite capable for the time being.

And last but not least writing the firmware had not been possible without all the info in this thread. Especially the layout picture by doctormord.

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