Datasheet

Version 0.6.6 of the Bluefruit LE firmware added the ability to use a new 'UUID128' flag to

add custom 128-bit UUIDs that aren't related to the parent service UUID (which is used when

passing the 16-bit 'UUID' flag).

To specify a 128-bit UUID for your customer characteristic, enter a value resembling the

following syntax:

Version 0.7.0 of the Bluefruit LE firmware added the new DESCRIPTION

and PRESENTATION keywoards, corresponding the the GATT Characteristic User

Description and the GATT Characteristic Presentation Format Descriptors.

The DESCRIPTION field is a string that contains a short text description of the characteristic.

Some apps may not display this data, but it should be visible using something like the

Master Control Panel application from Nordic on iOS and Android.

The PRESENTATION field contains a 7-byte payload that encapsulates the characteristic

presentation format data. It requires a specific set of bytes and values to work properly. See

the following link for details on how to format the

payload: https://developer.bluetooth.org/gatt/descriptors/Pages/DescriptorViewer.aspx?

u=org.bluetooth.descriptor.gatt.characteristic_presentation_format.xml

The following example shows how you might use both of these new fields:

For the Characteristic Presentation Format we have:

Format = IEEE-11073 32-bit FLOAT (Decimal 23, Hex 0x17)

Exponent = 0/None

Unit = Thermodynamic temperature: Degrees Fahrenheit (0x27AC) - Bluetooth LE Unit

List

# Add a custom characteristic to the above service using a

# custom 128-bit UUID

AT+GATTADDCHAR=UUID128=00-11-22-33-44-55-66-77-88-99-AA-BB-CC-DD-EE-FF,PROPERTIES

AT+GATTADDCHAR=UUID=0x2A37, PROPERTIES=0x10, MIN_LEN=2, MAX_LEN=3, VALUE=00-40,

DESCRIPTION=HRM Measurement, PRESENTATION=17-00-AC-27-01-00-00