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Original question:

ADS8332EVMV2-PDK: wrong sampling rate at the eval board GUI GUI

ADS8332EVMV2-PDK: can't use manual sampling mode

Roee Kimchi
Prodigy 120 points
Part Number: ADS8332EVMV2-PDK
Other Parts Discussed in Thread: ADS8332

Hi,

I am using the ADS8332 evaluation module kit.

when the channel select mode is Auto and I start from channel 0, there is no problem and the signal is shown perfectly.

when I am switching to manual mode and selecting the same channel, here is how it comes:

the same happens also on Auto selection mode when I don't start from channel 0.

I am sampling at the maximum sample rate (500KSPS).

the frequency does change when I change the input signal, but It doesn't shows the sine wave.

I need to use the manual channel select mode to be able to sample at full speed.

how can I fix this problem?

thank you!

  • 0
    TI__Guru 59876 points

    Hi Roee,

    Thank you for your post!

    I understand that you required the full 500 kSPS throughput, but does the issue resolved itself if you reduce the sample rate? Try 10x slower at 50 kSPS just for comparison and let us know.

    I will also check tomorrow whether I can reproduce the same issue on the EVM and we'll go from there.

    Regards,

    Ryan

  • 0 in reply to Ryan Andrews
    Prodigy 120 points

    Hi Ryan, thanks for your response!

    I also thought about aliasing , but the sampling rate is much higher than the Nyquist  frequency (1KHz signal and 500kSPS)

    manual mode worked fine for me until yesterday, and suddenly this problem occurred.

    the problem repeats when I switching to manual mode on different sample rates (also at 50kSPS as you suggested), and also the same signal appears for all of the channels, although I have only connected one of them.

    the only way to receive a reasonable image is to set it on Auto channel selection mode and start from channel 0. 

    if I start from any other channel at auto mode, the problem repeats.

    my thinking was that maybe there is some kind of synchronization problem when grabbing the data?

    thank you, very appreciate your help,

    Roee

  • 0 in reply to Roee Kimchi
    TI__Guru 59876 points

    Thanks, Roee. My concern was with some data capture or interface synchronization issue, which usually cleans up when the data rates are reduced. 

    Let me try to replicate this on the bench today and I'll see if I can reproduce the problem. 

    Regards,

    Ryan

  • 0 in reply to Ryan Andrews
    TI__Guru 59876 points

    Hi Roee, 

    So far I am not seeing the behavior you observed on the EVM. 

    In Auto mode, I'm able to start sampling from any channel and get proper results. Below, I have the same single-ended sine wave connected to CH2 and CH7. The input is 2 kHz with 2.5 Vpp, 2.048 V common-mode:

    Switching to Manual Mode, Channel 2 looks the same:

    What is the analog input signal amplitude and common-mode voltage that you are testing with? Also, can you share the GUI version number?

    Regards,

    Ryan