Analog Discovery 3 digital and analog input display

[qwertylex]

Can I display two analog channels at the same time as one digital channel in the same graph synced or at least two separate graphs synced?
And what is the lowest voltage for the digital channel to display a value on? I noticed 3.3V is mentioned but will it handle 1.8V or lower?

[attila]

Hi @qwertylex

In the Scope interface Add Channel/ Digital/ or View menu/Digital or use the Digital button in the toolbar. After this, if you want to show digital signals in the analog plot you can Add Custom Math channel and use the digital channel names.

The digital input logic threshold is about 1.5V so the 1.8V signals may not be detected correctly. You could help a bit with pull-up enabled from the Device options, like from the statusbar, the "100MHz" button, or Settings/Options/...

[qwertylex]

Thanks, and is the synchronization of the analog and digital inputs accurate at least within 100 μs of each other?

In other words, if I probed something that emitted a 1.8V pulse using both the digital and analog side, recorded both on one plot, how well would the pulse line up comparing the analog and digital plots to each other?

(I would test it myself but it hasn't arrived yet.)

[JColvin]

Hi @qwertylex,

This is what I'm seeing when I connect a 1.8 V DC signal to the Oscilloscope Channel 1 and Digital IO pin at the same time with no DIO pull.

Worst case scenario (which I'm defining in this post as from when the scope starts showing the input ramping up to when the digital input reports as logic high) is about 25 ns. I'd still probably go with internal pull-ups like Attila recommended since my test was only for a single data point.

Let us know if you have any questions.

Thanks,
JColvin