Common Initial Issues
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Device not visible: The devices are shipped in hibernate mode and are not discoverable. Connect to the USB cable and charge the device, on disconnecting the device will be discoverable.
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Cannot pair with device: There may be an active connection already formed that was not closed during device discovery. Briefly connect to USB and disconnect again to reset the device; then retry. For LE pairing issues, see the LE communication section.
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Cannot open a COM port: Firstly, view the device using the OS (e.g. device manager) to confirm that the OS has successfully installed the device and designated it a COM port number. Select the assigned COM port number using the terminal program and then connect. If this fails, try another terminal program; some terminal programs are not compatible with RFCOMM; try teraterm, a free open source terminal project.
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No response from device: For some OSs, the device may have formed more than one COM port for the device to expose the RFCOMM control channel; the data channel is usually port with the lower number. Also, check the behaviour of the return key for the terminal used; it may send a line feed (< LF>) instead of < CR>.