Is there any way to pause the AD9680 chip from sampling(only using the configuration on AD9680 chip, not FPGA).

Hi,

I wonder if there is any way to pause the AD9680 chip from sampling(only using the configuration on AD9680 chip, not FPGA).

I check the AD9680 documentation, I haven't found anything talks about how to pause sampling. I also looked at the following discussion, but unfortunately, it seems like the external trigger used in this pdf is implemented in FPGA. 

https://ez.analog.com/docs/DOC-17546-can-i-use-an-external-trigger-to-capture-data-from-ads7-v2ebz

I think the FPGA is buffering sample data from ADC (while ADC is always sampling non-stop). And a trigger event will trigger FPGA to find a certain amount of samples from the buffer. However, this implementation requires some memory resources on FPGA and I also need to take a lot of transmission delay into account, since the trigger is sync with ADC but not FPGA. I either need to shift the trigger signal or tell FPGA to take data from the data buffer at a shifted time.

My guess will be: there is no way to do this since AD9680 has a pipelined architecture, but I just want to confirm this. Or maybe there is another chip that has this feature? Do anyone have an idea?

Thanks!

 

Best wishes,

Chutao

  • 0
    •  Analog Employees 
    on Jul 20, 2018 12:00 AM

    Hi,

    You could put the ADC in standby mode. For more information please refer to the PDWN/STBY operation in the datasheet.

    Thanks

    Umesh

  • Hi UmeshJ,

    I notice that you can only do that through SPI bus. Let's say the ADC card starts with standby mode. It would take tens of nanosecond for us to write the register in AD9680(and the delay depends on SPI configuration). While AD9680 is one sample/nanosecond, I have already missed a lot of samples when the configuration is changed.  

    For the project I'm working on, time is very crucial. I need to start to sample immediately after the trigger signal at its rising edge. The tolerance is missing less than 10 samples.

    I think I will probably consider the TimeStamp feature(even though it is used for multi-chip synchronization). I will keep ADC sampling constantly. But use TimeStamp to label the data I want to start capturing. I might have other questions on TimeStamp. If I do, I will open another thread. The PDWN/STBY is still very helpful. I might need to disable it at some point. Thanks a lot.

    Best wishes,

    Chutao

  • 0
    •  Analog Employees 
    on Jul 20, 2018 5:21 AM

    Hi Chutao,

    timestamp is a good option too.

    Umesh