AD2 - How does record work?

[krbvroc1]

Hi all, every time I use Waveforms, I seem to have trouble understanding some of the terminology or concepts.

I am trying to troubleshoot some I2C lines on a device that locks up after a 20-40 minutes. I thought the Record feature would stream and capture all the data, but I am not sure what to do with the data.

I let the record run for about 40 minutes, came back to the computer and saw the I2C lockup had occurred. I stopped the recording (default.bin). But what do I do with it? I tried File -> Import Binary and 'Show Entire capture'. It says the file has 42,329,550 bytes @ 7.692MHz. That is only  2.6seconds worth of data. Where is all the rest of the data that I thought I captured?

[attila]

Hi @krbvroc1

I don't know how did you configure the capture.
Such scenarios should be detected with trigger, like a timeout trigger on SDA.
On I2C level this is usually caused by a glitch on the SCL which the slave interprets as additional pulse so the master-host goes out of bit sequence. Like the master wants to generate nak or stop, where the slave should have released the SDA, but the slave already wants to send the next word bits, holding the SDA low.
To recover from this, the master should pulse the SCL line until the SDA is released then generate a stop.

[krbvroc1]

Hi @attila

I appreciate the tip about the pulse trigger. Stepping back for the big picture can you explain how the record data feature works and where the data is that I thought I captured? Why was there only a few seconds of data when I thought I captured for 40 minutes? My plan was to look at the recorded data and see what the state of the SCL line was. And is there a way to 'playback' recorded that say analysis can be done like the trigger you mention?

[attila]

Hi @krbvroc1

As you can see the record length is limited to max 256Mi samples.

[krbvroc1]

@attila

Well that seem pretty useless, I thought the whole point of recording to disk was to save/stream unlimited lengths of data?

My screen looks as below and it indicates I could record 2hr.

[attila]

Hi @krbvroc1

Try to use some trigger to capture the event you are interested in.

On 9/28/2023 at 1:13 PM, attila said:

The 'Record to File' only saves data to file to be process by external applications.