These directions by Henry Walker

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I noted difficulties in connecting to the Scribbler 2 over Bluetooth on Debian Linux. The problem involved various error messages, including some "permission denied" text.

For those in similar situations, I want to pass along the following: Create the file


containing the single line

        KERNEL=="rfcomm*", GROUP="dialout", MODE="0666"

This ensures that the udev subsystem for dynamic device management creates the rfcomm devices with permissions that allow anyone to use them. After each access, the system seems to reset its permission codes for rfcomm. Thus, even if rfcomm0 is set manually to allow user access, the system removes the access privilege without this line,

With this file/line added, I have been able to consistently access a Scribbler 2 robot via Bluetooth from the workstation, once the robot's Bluetooth pairing has been established.

In the Gnome/Debian environment, establishing the pairing should be straightforward: one uses the Gnome menu to select System==>Preferences==>Bluetooth. One then sets up the new device, sets the pass key to 1234, and lets the system do the rest. Unfortunately, the system often ignores the given pass key and fails to make the pairing. The best approach here seems persistence, although new users may wonder what is going wrong. For example, last night, it took me 8 tries to use the Gnome wizard to finally establish the pairing with 1234 as pass key.

From Derek Schuurman: Similar difficulties can be encountered under Linux using a direct serial cable connection. I am using Ubuntu Linux, and unless a user has the proper privileges, they cannot read or write to the serial port (in my case, the device is /dev/ttyS0). In Ubuntu 11.04, they need to be a member of the "dialout" group to use the serial port. Of course, one can manually chmod the device file, but this only lasts until the next re-boot. Setting up a similar udev rule to set the mode bits for the serial device should allow regular users access to the serial port.