Cable-mode pairing process AIRcable Serial and USB

The AIRcable Serial is a RS-232 serial cable replacement device which compiles to the industrial standard EIA-232-E. There are three different versions available: The DTE has a Sub-D 9 pin female connector, the DCE has a Sub-D 9 pin male adapter and the AIRcable USB is a serial-to-USB adapter.

Note: This procedure will not work if the AIRcable devices have been configured before using one of the automatic connection mode "Service-Slave" or "Service-Master". Please refer to the Command Line Interface to reset the AIRcable modules (^A Z).

See section on "Hardware Handshake" below.

Pairing in "Cable Mode"

The AIRcable Serial modules come unpaired (in fact the are paired with our test system). You have to establish a relationship with your other Bluetooth device first before they are operational.

During this pairing process, security information is exchanged and the two devices are bonded together. After the pairing process the two devices are bonded and no other Bluetooth device can discover or make a connection with these devices. The connection is secure.

There is a button hidden under a hole marked "pairing" in each of the modules. During this process please make sure that no other Bluetooth device is in range.

  1. Switch to the baud rate you will use with the AIRcable Serial
  2. Plug in the external power supply
  3. Press and hold the button for 5 seconds, or until the green light goes out (Power LED). The blue Connection LED will start flashing rapidly
  4. Now switch the baud rate on the other AIRcable Serial module
  5. Plug in the external power supply, or power the module with 5V through pin 9
  6. Press and hold the button for 5 seconds, or until the green light goes out. The Connection LED will start flashing rapidly
  7. Decide which one should be the master (initiating the connection), e.g. the AIRcable USB
  8. Press the button (short click) on this device. The Connection LED will start blinking slowly. The two devices will pair now
  9. If the Connection LED is steady now, the modules are ready to use. The Connection LED will stay on when a connection has been established.

Delete Pairing Information

To delete all pairing information follow this procedure. It is important that no other Bluetooth device is discoverable and in range during this procedure. Delete the pairing from each module separately without having the other device plugged in.

Note: after deleting the pairing information the Connection LED stays off, even if it is plugged in. Press the button (short press) to start the pairing process again.

Light Indicators

The AIRcable has two LEDs for power and connection status.

Power LED off no power supply
Power LED on firmware running ok
Connection LED off no pairing established
Connection LED fast blinking waiting for a connection (slave)
Connection LED slow blinking discovering and attempting a connection (master)
Connection LED very slow blinking security key exchange during pairing
Connection LED on connection established


Baud rate Selection

The AIRcable Serial provides switches accessible from the top to select the baud rate.

SW1 SW2 SW3 Baud Rate
0 0 0 31.25 kbit/s
0 0 1 19.2 k
0 1 0 4.8 k
0 1 1 56.7 k
1 0 0 4.8 k
1 0 1 38.4 k
1 1 0 9.6 k
1 1 1 115.2 k

Hardware Handshake

SW4: on (up) - hardware handshake enabled

The new AIRcable Serial and AIRcable USB devices have a new feature that will allow you to disable and enable hardware handshake, causing the RTS/CTS connection to no longer be required. However, the RTS/CTS lines are used to control traffic over the air. Disabling hardware handshake can lead to data loss when/if the buffers overrun, but data loss is unlikely. Hardware handshake is enabled by default.

The difference between with the hardware handshake involving the AIRcable Serial module and the AIRcable USB module is that the AIRcable Serial module has a switch on the device that will allow you to disable hardware handshake where the AIRcable USB module has a software configurable "switch" that will allow you to disable hardware handshake, but lacks a switch on the outside of the device. The AIRcable USB's software "switch" also disables other handshake lines such as DTR, DSR, and DCD as well.

Some hardware devices do not need hardware handshake and don't have RTS/CTS lines available. If this is the case, you can disable hardware handshake using the 4th dip switch on the module. Switch it to off (down) to disable hardware handshake. The AIRcable modules will transmit data no matter if the device is ready to receive any data or not.

The AIRcable USB has a software configuration to disable hardware handshake. This is used when some Windows application cannot initialize the virtual COM port correctly (Visual Basic, etc.). Use the Command Line Interface to disable hardware handshake on the USB. (^A K 1)

Note: The software configurable hardware handshake only works on the AIRcable USB. It also disables all other RS232 handshake lines (DTR, DSR, DCD). On the AIRcable Serial this configuration only disables the RS232 handshake lines (DTR, DSR and DCD). It does not switch off hardware handshake. Use the DIP switches as described above.