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Rigol DHO stops transferring data at 200K

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luis garcia:
I set the memory depth to 1M.
Then I capture some signal on channel 1. All remaining channels are off.
From my PC i open the instrument using Visa, select source channel1, data format Byte, mode Raw, start=1 and stop=1M, and then read the waveform. I read the waveform length from the data itself and the number is correct, 1M.
However, when reading the actual data, It stops at 200K with error "VI_Error_IO".
Below 100K it works well. Beyond that it always stops at 200K.
The PC is connected to the instrument by USB.

Anything I am missing perhaps?


In the older Rigol DSOs, like DS1000Z, DS2000A etc., you can only read the data in blocks of ~ 100 kB to ~ 200 kB. With :WAV:STARt/STOP the desired data are selected. Maybe it is the same with your DHO.


luis garcia:
Thanks for yor answer Peter. It makes sense.

However I do not see it working as expected.
If I change start and stop points i need to perform a ":wav:data?" again. But if I do this, the memory pointer is reset to zero and what i read is the first 200K again.
If I set the start and stop points after "wav:data?" the read timeouts, apparently because setting start and stop points resets the buffer.

So, my question now is: if I want to read by chunks of 200K, which of the following is the correct approach?

1. Wav:data?; Wav:start; Wav:stop; read data
2. Wav:start; Wav:stop; Wav:data?; read data
3. ???


I looked in old code of mine, I used the following:


Send & Read:


luis garcia:
I see no difference placing the PRE? after DATA?.
I can see the PRE command reads all parameters and they look fine.
But it behaves as I explained above.

This is my second Rigol device. The first one, the DHO4, had to be returned. I have no much experience with this brand.
Everything looks promising with DHO1000. Reading the buffers was essential to me and is not working as expected. I was happy to see that the unit came with USB3 instead of USB2. But everything is fading away now.:-(


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