Different behavior between Raspberry PI and PC

[Loic VINET]

Hello,

I'm using a Digital Discovery with a Raspberry and a Windows PC, and running the same Python program on both computers.
I don't have the same acquisition between them.

Here is my test:
I have DIO out 31 connected to DIO In 12.
The program does not emit any custom signals from the dio 31.
But with the raspberry, I get data in dio In 12, and I get nothing with the windows PC which is normal, I should have nothing.
When I disconnect dio out 31 from dio in 12, the raspberry does not give any data from dio in 12, which is normal.

I have no idea what could explain this difference in behavior.

[attila]

Hi @Loic VINET

Are you driving DIO 31 or 12 or using pull up/down ?
If not, these are in high impedance which can capture any radiation, specially if wires are connected to it, usually the 50/60 Hz from electrical grid.
In a setup the ground may be floating (power supplies without earth connection like most of USB chargers) or connected to earth (some laptop supplies and most computers), which also influence noise reception.

[Loic VINET]

Hi @attila

No I am not driving dio 31 and 12. I have just a wire between 31 and 12.

I have a trigger generate by dio 25 to dio 15.

When I run the PC windows program I see no data

When I run the raspberry program I see data

When I disconnect the wire and run the raspberry program I see no data 

This is very strange...

[attila]

Hi @Loic VINET

18 hours ago, attila said:

If not, these are in high impedance which can capture any radiation, specially if wires are connected to it, usually the 50/60 Hz from electrical grid.
In a setup the ground may be floating (power supplies without earth connection like most of USB chargers) or connected to earth (some laptop supplies and most computers), which also influence noise reception.