Why won't my Bluetooth keyboard pair with my desktop?

Question

I have a Microsoft Wedge Bluetooth keyboard and no matter what I do, it won't pair with my ASUS BT400 USB Bluetooth adapter. Using bluetooth-wizard, I can discover the keyboard:

When I select it and click "Continue", the following text is displayed for about 30 seconds:

"Connecting to 'Microsoft Wedge Mobile Keyboard'..."

Then the following message is displayed:

"Setting up 'Microsoft Wedge Mobile Keyboard' failed"

The last few relevant lines from /var/log/syslog include:

Oct 16 22:11:36 nathan-desktop bluetoothd[849]: Discovery session 0x7f3ac3bacd70 with :1.132 activated
Oct 16 22:11:44 nathan-desktop bluetoothd[849]: Unknown command complete for opcode 37
Oct 16 22:11:57 nathan-desktop bluetoothd[849]: Unknown command complete for opcode 37
Oct 16 22:12:04 nathan-desktop bluetoothd[849]: Stopping discovery
Oct 16 22:12:07 nathan-desktop bluetoothd[849]: Unknown Management opcode 23 (index 0)
Oct 16 22:12:37 nathan-desktop bluetoothd[849]: hci0: Cancel Pair Device (0x001a) failed: Invalid Parameters (0x0d)

The output of lsmod | grep bt:

nathan@nathan-desktop:~# lsmod | grep bt
btusb                  32412  0 
bluetooth             391136  30 bnep,btusb,rfcomm

Other Details:

• Ubuntu 14.04 64-bit
• Kernel version: 3.13.0-36
• Keyboard works fine with Nexus 5 and used to work in Precise on an older HP laptop
• USB audio (A2DP) works fine on the Bluetooth adapter
• The keyboard is well within range of the adapter

Answer 1

I finally found a command that worked:

sudo hciconfig hci0 sspmode 0

This command sets Secure Simple Pairing mode to 0 for the device hci0. This was a new pairing mechanism introduced in the Bluetooth 2.1 spec. However, it seems to cause trouble with my keyboard and disabling it solved the problem for me.

There is still one downside - the setting doesn't persist. That means I need to run the command on every boot. I'm still searching for a way to make the setting persist.

_{Source: http://www.raspberrypi.org/forums/viewtopic.php?f=28&t=37482}