WaveForms Logic Amplitude (Y) Plot Scale

[edtriccorp]

Hello, 

I am tinkering with my Analog Discovery 2 as a logic analyzer for the first time and I cannot seem to find a way to make the amplitude scale more visible or a way to zoom in. The time base (X) seems pretty easy enough but the plot/graphics stays very squished. Is there a way to adjust this or set it? I am hoping I am missing something very obvious or hopefully missed it in a different part of the help/web help manual? I want to achieve a legible plot along with protocol/data analyzer display. I have been married to a Saleae Logic Analyzer but hoping to take advantage of the integrated instruments the Discovery 2 /Waveforms offers.

Thank you,

Wess

 

 

[attila]

Hi @edtriccorp

The analog representation of the digital values is auto scaled between minimum and maximum value, for 8 bit UART from 0 to 255.
This is useful for data transmission over parallel bus, SPI, I2C, I2S...
Currently it does not have manual scaling option, but if you think it is needed I can add such.

[edtriccorp]

Hi @attila, 

Interesting. In reviewing the plot you shared and in reviewing my original description/question I realized that perhaps I am asking the wrong question. Does the software automatically include some kind of analog plot/data that is always overlayed with the logic plots similar to what you are showing?  

From my exposure to logic analyzers what we are really interested in are just High (H) / Low (L) thresholds (1.8V, 3.3V, 5V, etc... normalized to 1 or 0 etc...), the time base scaling, and perhaps in more fancy or advanced analyzers the protocol/decoding. Based on the plot you shared would it be reasonable for me to infer that the analog data is what is is throwing off the logic plots (Y scale?) ? Since we are only interested in 0 or 1 like levels if analog 0 to 255 is overlayed 0 to 1 gets drowned out no? 

The Analog Discovery 2 / WaveForms software is proving difficult for me to lock into (zoom in/out) to my logic signal in any kind of expedient or easy way. I have to search pretty hard for the signal and even when I ultimately find it it is not so pretty in scale, timebase, and packet from a visual point of view. I am sharing a couple of plots from my other logic analyzer software that hopefully provides some sense of what I am attempting describe here. 

The output is from a UART TX line at 115200bps. Scaling the time base keeps the protocol decode/text displayed nicely and the signal zooms in/out centered around the mouse pointer for example. Very easy to zoom and pan and read the text no matter the time base and no matter where I am in the signal. The signal is instantly displayed this way the instant the channel is enabled and I dont have to spend much time getting it dialed in for viewing. I have yet to discover if I can do this in WaveForms. 

 

 

 

Edited July 5, 2023 by edtriccorp

[attila]

Hi @edtriccorp

1. You can use add Digital channels in Scope to capture analog and digital inputs at the same time.
2. For traditional logic analyzer operation mode use the Record Mode in Scope and Logic Analyzer.
3. If you are only interested in the digitally transmitted data use the Protocol 'spy' tools.

[edtriccorp]

Hi @attila

I understand the instruments and the use cases I guess they are just not behaving "as I would expect" ... With my Saleae I just monitor the signal and it streams the data I need along with the decoder/protocol analyzer in real-time with very little effort.

With WaveForms I really seem to have to search hard for the right scale and when I eventually find it something on my screen/display is distorted and becomes not so readable. Take for example your last screen shot. It displays ~3 bytes in a very small "y scale" and when I try to view more than 3 bytes and change the time base to fit more bytes I basically cant read or make out the plots/decode text not to mention there is significant lag in the screen/refresh of the plots. This seems to be the case on both my Windows 11 version and Ubuntu 22.04. The record option I assume is a non real time post record view? I am trying to view/stream in real time but it becomes very impractical to zoom/scale the logic signal while maintaining a legible view or reading of the screen Am I missing something fundamental here? 

[edtriccorp]

Hi @attila

 

OK. It looks like I have some new information. I was using the logic analyzer with the Diligent BNC board in between the Analog Discovery 2 and the Logic Channels. If i remove the BNC board then WaveForms behaves much more as expected. Why would this be the case? The board only has a few jumpers for AC/DC on for the scope probes and then impedance jumpers. I would expect the digital I/O breakout to be unaffected and that seems to be the case from the  schematics and the documents. ??? It all seems to work now but I have no idea why? 

[attila]

Hi @edtriccorp

The BNC adapter can slightly increase the input capacitance and crosstalk on the DIO lines due to the longer traces.
It is important to have good GND connection between the devices and circuits, use more GND wires to reduce resistance.
To reduce the crosstalk on the flying wires use twisted signal wires with GND, specially for the critical like clock and chips select signals.