We have a very simple RS485 to USB cable connection on our automotive inspection equipment.
To sum up the issue, we are having drops in communications between our board and any laptop that is charging!
No failures when the laptop is on battery. No failures when using a Desktop PC. We use a half-duplex configuration
and a max cable length of 20 meters, but our 8 meter cables seem to fail more often for some unknown reason.
Here is the microprocessor side. Cable connects to the 3-pin connector.

Here is a shot of the cable. J1 connects to the 3-pin above. Black and Red are the diff pair. White is Ground.
Drain wire is the shield. Cable shield is grounded to the USB case. No schematic for the dongle circuitry, although I
do see a micro and an RS485 converter IC.

We are starting to think it is a Ground issue - noise or Ground loop or something similar.
Thanks in advance for the help.
To sum up the issue, we are having drops in communications between our board and any laptop that is charging!
No failures when the laptop is on battery. No failures when using a Desktop PC. We use a half-duplex configuration
and a max cable length of 20 meters, but our 8 meter cables seem to fail more often for some unknown reason.
Here is the microprocessor side. Cable connects to the 3-pin connector.

Here is a shot of the cable. J1 connects to the 3-pin above. Black and Red are the diff pair. White is Ground.
Drain wire is the shield. Cable shield is grounded to the USB case. No schematic for the dongle circuitry, although I
do see a micro and an RS485 converter IC.

We are starting to think it is a Ground issue - noise or Ground loop or something similar.
Thanks in advance for the help.