Mega 2650 reacting different if other laptop is used

Dear community,

if i connect my Mega2650 using a 30 feet active USB cable to my fairly new ASUS laptop with Win 8.1 my project (Baseball scoreboard) is working perfectly.

The final solution at the field itself should use an older Acer Aspire 5720 with Win 7 32bit (SP 3) to control the scoreboard. All the latest drivers are installed and the Acer laptop is recognizing the Arduino Mega and uses the same com port and settings as the ASUS. But if i try to control the scoreboard it does not receive any data.

Anyone having an idea what the root cause could be? Thx in advance Cheers Wolf


Is it possible to try the Acer with a much shorter USB cable?

Hi Steve,

unfortunately not. I tested the Acer with an Arduino Uno with a short cable.. that works.

Meanwhile i used another older Fujitsu laptop which was working perfectly with the long cable too.

As well i tested with an additional active USB hub on the Acer ... but no improvement.

Wait - so it detects the COM port, and doesn't barf when you try to use the COM port, but the board doesn't respond correctly, but it does work with a shorter, non-active cable?

That is incredibly bizarre. I cannot fathom how it could be able to communicate enough to recognize the USB serial adapter whilest failing to actually use it...

Is it a USB 3.0 port (the plastic part of the connector is blue if it's USB 3.0)? USB 3.0 ports, particularly on older machines, often behave oddly with non USB 3.0 devices.

Ï’m assuming your PC is talking to the Mega via one of the Mega’s serial ports?

Since the USB layer appears to work, could you try the loopback test, to check that the encapsulated serial layer is working?