Texas Instruments CC2541 - Page 53

www.ti.com Generic Attribute Profile (GATT)
53
SWRU271H–October 2010–Revised April 2019
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The Bluetooth Low Energy Protocol Stack
5.5.4.2.1 Attribute Table Definition
Each service or group of GATT attributes must define a fixed size attribute table that gets passed into
GATT. This table, in simpleGATTProfile.c, is defined as follows:
Each attribute in the following table is of the type:
The elements of this attribute type are as follows:
• type: This is the UUID associated with the attribute. This UUID is defined as the following:
The length can be either ATT_BT_UUID_SIZE (2 bytes), or ATT_UUID_SIZE (16 bytes). The *uuid is a
pointer to a number either reserved by Bluetooth SIG (defined in gatt_uuid.c) or a custom UUID in the
profile.
• Permissions – This element enforces how and if a GATT client device can access the value of the
attribute. Possible permissions are defined in gatt.h as the following:
– GATT_PERMIT_READ // Attribute is Readable
– GATT_PERMIT_WRITE // Attribute is Writable
– GATT_PERMIT_AUTHEN_READ // Read requires Authentication
– GATT_PERMIT_AUTHEN_WRITE // Write requires Authentication
– GATT_PERMIT_AUTHOR_READ // Read requires Authorization
– GATT_PERMIT_ENCRYPT_READ // Read requires Encryption
– GATT_PERMIT_ENCRYPT_WRITE // Write requires Encryption
Section 5.4 describes authentication, authorization, and encryption further.
• Handle – This is a placeholder in the table where GATTServApp assigns a handle. Handles are
assigned sequentially.
• pValue – This is a pointer to the attribute value. The size cannot be changed after initialization. The
maximum size is 512 octets.
The following sections provide examples of attribute definitions for common attribute types.