IIO Oscilloscope plot channel display issue with multiple AD4020 devices

Channels will be grouped based on the driver naming. So my guess is that in your device tree you do not have unique names for the individual drivers which have the associated buffered channels. This is why the grouping in IIO-Scope is getting confused.

Note that IIO-Scope cannot capture from multiple drivers simultaneously in the same capture window.

-Travis

Channels will be grouped based on the driver naming. So my guess is that in your device tree you do not have unique names for the individual drivers which have the associated buffered channels. This is why the grouping in IIO-Scope is getting confused.

Note that IIO-Scope cannot capture from multiple drivers simultaneously in the same capture window.

-Travis

Hi Travis,

When you say IIO-scope can't capture from multiple drivers, does that mean that I need to do this from a python script instead?  It does look like I'm getting 4 separate and different channels of data displayed in IIO scope, so do you mean that the data might only be for one channel, just duplicated/offset/sliced in some way that maybe isn't obvious from an initial reivew?

This is what I've got for the 4 ADCs in the devicetree.dts file inside an axi-spi_engine_x instance.  They each have a unique label there, is that what you mean?

ad4020_0: adc@0 {
compatible = "ad4020";
<snip>

};

<snip>

ad4020_2: adc@0 {
compatible = "ad4020";
<snip>
};

<snip>

ad4020_3: adc@0 {
compatible = "ad4020";
<snip>
};

<snip>

ad4020_4: adc@0 {
compatible = "ad4020";

<snip>
};

I've also put the relevant iio_info output here in case that helps:

iio:device0: ad4020 (buffer capable)
1 channels found:
voltage0: (input, index: 0, format: le:s20/32>>0)
3 channel-specific attributes found:
attr 0: offset value: -1048576
attr 1: raw value: 976412
attr 2: scale value: 0.002384185
1 device-specific attributes found:
attr 0: sampling_frequency value: 1800000
3 buffer-specific attributes found:
attr 0: data_available value: 0
attr 1: length_align_bytes value: 8
attr 2: watermark value: 400
1 debug attributes found:
debug attr 0: direct_reg_access value: 0x63
iio:device1: ad4020 (buffer capable)
1 channels found:
voltage0: (input, index: 0, format: le:s20/32>>0)
3 channel-specific attributes found:
attr 0: offset value: -1048576
attr 1: raw value: 792238
attr 2: scale value: 0.002384185
1 device-specific attributes found:
attr 0: sampling_frequency value: 1800000
3 buffer-specific attributes found:
attr 0: data_available value: 0
attr 1: length_align_bytes value: 8
attr 2: watermark value: 400
1 debug attributes found:
debug attr 0: direct_reg_access value: 0x63
iio:device2: ad4020 (buffer capable)
1 channels found:
voltage0: (input, index: 0, format: le:s20/32>>0)
3 channel-specific attributes found:
attr 0: offset value: -1048576
attr 1: raw value: 21551
attr 2: scale value: 0.002384185
1 device-specific attributes found:
attr 0: sampling_frequency value: 1800000
3 buffer-specific attributes found:
attr 0: data_available value: 0
attr 1: length_align_bytes value: 8
attr 2: watermark value: 400
1 debug attributes found:
debug attr 0: direct_reg_access value: 0x63
iio:device3: ad4020 (buffer capable)
1 channels found:
voltage0: (input, index: 0, format: le:s20/32>>0)
3 channel-specific attributes found:
attr 0: offset value: -1048576
attr 1: raw value: 831778
attr 2: scale value: 0.002384185
1 device-specific attributes found:
attr 0: sampling_frequency value: 1800000
3 buffer-specific attributes found:
attr 0: data_available value: 0
attr 1: length_align_bytes value: 8
attr 2: watermark value: 400
1 debug attributes found:
debug attr 0: direct_reg_access value: 0x63

Thanks now,

Michael.

Can you post the full device tree? Posting a pastebin or github gist link would be ideal.

-Travis

Hi Travis,

This should be a link to the relevant pastebin of the source devicetree I'm compiling.

https://pastebin.com/raw/iDT8Z8sD

Hi Travis,

I was able to capture multiple deivces simultaneously with IIO-Scope - see below screenshot

One difficulty I had was to do a FFT which was only working for the first channel, but the other ones were giving an error in the terminal

How are the DMAs connected in HDL? Do you want all ADC to map to one DMA?

-Travis

It is likely you are timing out depending on how the enables are setup in HDL. When controlling individual channels how are you mapping data into the DMA(s)?

The way your device tree is written tells me that you should have 4 DMAs, each with 1 channel. Is this what you want?

-Travis

Yes, we have 4 x DMAs each with 1 channel used in the current design.

In that case, IIO-Scope should enumerate 4 devices each with 1 channel. Not where all the channels appear under one device. My guess is that IIO-Scope is getting confused since all the drivers have the same name.

Let me check with one of the IIO-Scope developers to see what happens in this case. I think we usually assume they are all different.

-Travis

Looking at the code for IIO-Scope, it currently assumes devices have unique names. Otherwise, it will improperly relate channel names. A ticket was made to fix this. In the meantime, I would recommend updating the device tree to give unique names to the driver entries.

-Travis

Hi Travis,

I think I've changed all the node names to be unique, but I'm still seeing the same behavior in iio scope. Should it be fixed with the updated dts, or will this require an updated version of IIO scope?

Updated dts here in case I'm missing something in terms of the device names. ://pastebin.com/raw/AWdQGN3u