I2S line connects only when probe is on

MisterBill2

Joined Jan 23, 2018
8,485
OK, but if it offers some improvement . that scope trace hows ringing on both edges of the square wave signal, which may be the problem. Certainly ringing is not what should be present. Before continuing I suggest adjusting the cope probe using the scope probe adjust source, to make sure that it is not a probe artifact. Then try a slightly larger cap in series with the resistor, 20pF or possibly 27pF, depending on what is on hand.
One other thought comes to mind is about the connection cable between the devices. Is that supposed to be 50 ohm coaxial and instead some high impedance microphone cable? The lower impedance higher capacitance cable may be the intended load for that driver device.
 

Thread Starter

italiansoccer19

Joined Apr 19, 2021
16
OK, but if it offers some improvement . that scope trace hows ringing on both edges of the square wave signal, which may be the problem. Certainly ringing is not what should be present. Before continuing I suggest adjusting the cope probe using the scope probe adjust source, to make sure that it is not a probe artifact. Then try a slightly larger cap in series with the resistor, 20pF or possibly 27pF, depending on what is on hand.
One other thought comes to mind is about the connection cable between the devices. Is that supposed to be 50 ohm coaxial and instead some high impedance microphone cable? The lower impedance higher capacitance cable may be the intended load for that driver device.

I tried 1x probe and it gave me noisy results similar to the 10pf in parallel with 10M
 

MisterBill2

Joined Jan 23, 2018
8,485
I suggested trying a lightly larger capacitance since what I thought the response was is that it sort of worked with the first SERIES RC arrangement. My comment about the probe was related to setting the probe compensation capacitor adjustment. If that is not possible then please ignore that part of the comment.
 

Thread Starter

italiansoccer19

Joined Apr 19, 2021
16
I suggested trying a lightly larger capacitance since what I thought the response was is that it sort of worked with the first SERIES RC arrangement. My comment about the probe was related to setting the probe compensation capacitor adjustment. If that is not possible then please ignore that part of the comment.
https://www.circuitspecialists.com/hp-9060.html

According to the link above, what values should I try ? This is the probe that 10x work on

So the probe is set to 10 x, and the oscilliscope has 1Mohm + 18pF in parallel.

Based on these two things what circuit shall I build to mimic the 10x prob e effect ?
 

MisterBill2

Joined Jan 23, 2018
8,485
The first time suggested 10 Megohms and ten Picofarads, and the report was that part of it worked , in post #22. So next I suggested a eries connection, 10Megohms and 20 or 27pF, depending on which value of capacitor is most convenient. The mention about the cope probe was not part of the test.
 

Thread Starter

italiansoccer19

Joined Apr 19, 2021
16
The first time suggested 10 Megohms and ten Picofarads, and the report was that part of it worked , in post #22. So next I suggested a eries connection, 10Megohms and 20 or 27pF, depending on which value of capacitor is most convenient. The mention about the cope probe was not part of the test.
So let me confirm :

10Mohm + 20pF in series

Correct ?
 
Usually, if it is a standard scope with a 3-prong cord, ground of the probe is earth.

If it is say adapter powered and the adapter has a grounded cord, it's POSSIBLE that one side of the supply is Earth.
 
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