Raspberry Pi Microcontrollers - Revision history

Kai: /* GATT Profiles, Services, Characteristics, and Descriptors */

2025-05-09T23:08:31Z

GATT Profiles, Services, Characteristics, and Descriptors

← Older revision		Revision as of 2025-05-09T23:08:31
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	* DYNAMIC: Indicates that reading and writing to this characteristic requires adding this case to the read and write callbacks.		* DYNAMIC: Indicates that reading and writing to this characteristic requires adding this case to the read and write callbacks.

	We expect the BTstack Python script to generate GATT profile data as described on the page [[GATT Profile Data in Bluetooth Low Energy]]. However, the script leaves out the Client Characteristic Configuration attribute when the declaration of the characteristic in the BTstack ''.gatt'' file does not include a NOTIFY or INDICATE keyword in the permissions section. ~~Many~~ popular BLE scanner applications ~~rely on the presence of the Client Characteristic Configuration attribute~~, ~~however, in order to extract the characteristic value access permissions.~~ '''~~Manual editing~~ of the generated GATT profile data is needed if script~~-generated attributes do~~ not satisfy our needs.'''		We expect the BTstack Python script to generate GATT profile data as described on the page [[GATT Profile Data in Bluetooth Low Energy]]. However, the script leaves out the Client Characteristic Configuration attribute when the declaration of the characteristic in the BTstack ''.gatt'' file does not include a NOTIFY or INDICATE keyword in the permissions section. It also generates GATT profile data incompatible with most popular BLE scanner applications '''when combining WRITE_WITHOUT_RESPONSE with NOTIFY'''. Therefore, '''manual tweaking of the generated GATT profile data may be needed if the output of the script does not satisfy our needs.'''

	==== The BTstack runloop ====		==== The BTstack runloop ====

Kai: /* Bluetooth with BTstack */

2025-05-09T22:31:28Z

Bluetooth with BTstack

@@ Line 125: / Line 125: @@
 * DYNAMIC: Indicates that reading and writing to this characteristic requires adding this case to the read and write callbacks.
-===== BTStack Python script output for a GATT characteristic declaration attribute =====
+We expect the BTstack Python script to generate GATT profile data as described on the page [[GATT Profile Data in Bluetooth Low Energy]]. However, the script leaves out the Client Characteristic Configuration attribute when the declaration of the characteristic in the BTstack ''.gatt'' file does not include a NOTIFY or INDICATE keyword in the permissions section. Many popular BLE scanner applications rely on the presence of the Client Characteristic Configuration attribute, however, in order to extract the characteristic value access permissions. '''Manual editing of the generated GATT profile data is needed if script-generated attributes do not satisfy our needs.'''
 ==== The BTstack runloop ====

Kai: Adds description of the binary sequence of a GATT attribute for a characteristic value

2025-05-09T22:12:43Z

Adds description of the binary sequence of a GATT attribute for a characteristic value

← Older revision		Revision as of 2025-05-09T22:12:43
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	===== BTStack Python script output for a GATT characteristic declaration attribute =====		===== BTStack Python script output for a GATT characteristic declaration attribute =====

	Let's have a look at the output of the BTstack Python script that converts the .gatt file to a C header and let's narrow it down to just the characteristic ~~declarations~~.		Let's have a look at the output of the BTstack Python script that converts the .gatt file to a C header and let's narrow it down to just the characteristic attributes (descriptors).

	Here is the binary sequence (in hex representation) generated for an attribute that declares a GATT characteristic with attribute UUID ''B0B0F155-B0B0-B0B0-B0B0-B0B000000101'' and permissions ''READ \| DYNAMIC''		Here is the binary sequence (in hex representation) generated for an attribute that declares a GATT characteristic with attribute UUID ''B0B0F155-B0B0-B0B0-B0B0-B0B000000101'' and permissions ''READ \| DYNAMIC''
Line 166:		Line 166:
	\|}		\|}

	===== BTStack Python script output for a GATT user description ~~declaration~~ attribute =====		===== BTStack Python script output for a GATT characteristic value attribute =====

			<pre>
			0x16, 0x00, 0x02, 0x03, 0x09, 0x00, 0x01, 0x01, 0x00, 0x00, 0xb0, 0xb0, 0xb0, 0xb0, 0xb0, 0xb0, 0xb0, 0xb0, 0x55, 0xf1, 0xb0, 0xb0
			</pre>
			The bytes are grouped from left to right as follows:
			* 2 bytes for the length of the attribute: 0x0016 (= 22 bytes)
			* 2 bytes for the permissions (properties) of the attribute: 0x0302 (= read-only, dynamic, 128-bit UUID)
			* 2 bytes for the handle of the attribute: 0x0009
			* 16 bytes for the UUID of the characteristic that the value is associated with: 0xb0b0f155b0b0b0b0b0b0b0b000000101

			===== BTStack Python script output for a GATT characteristic user description attribute =====

	<pre>		<pre>

Kai: /* BTStack Python script output for a GATT user description declaration attribute */

2025-05-09T20:49:23Z

BTStack Python script output for a GATT user description declaration attribute

← Older revision		Revision as of 2025-05-09T20:49:23
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	<pre>		<pre>
	0x08, 0x00, 0x0a, 0x01, 0x0a, 0x00, 0x01, 0x29,		0x08, 0x00, 0x0a, 0x01, 0x0a, 0x00, 0x01, 0x29
	</pre>		</pre>

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	* 2 bytes for the handle of this attribute		* 2 bytes for the handle of this attribute
	* 2 bytes for the 16-bit short UUID that indicates a user description attribute: 0x2901		* 2 bytes for the 16-bit short UUID that indicates a user description attribute: 0x2901
			where the order of the bytes in each group needs to be reversed before analyzing.

			The attribute declaration does not include the user description text itself. User description text is always "dynamic", meaning that it is served to the client on demand on the basis of the attribute handle. In BTstack, the implementation of the read callback is responsible for returning the UTF-8 bytes for the text string corresponding the attribute handle.

	==== The BTstack runloop ====		==== The BTstack runloop ====

Kai: /* BTStack Python script output for a GATT user description declaration attribute */

2025-05-09T20:21:13Z

BTStack Python script output for a GATT user description declaration attribute

← Older revision		Revision as of 2025-05-09T20:21:13
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	0x08, 0x00, 0x0a, 0x01, 0x0a, 0x00, 0x01, 0x29,		0x08, 0x00, 0x0a, 0x01, 0x0a, 0x00, 0x01, 0x29,
	</pre>		</pre>

			The bytes are grouped from left to right as follows:
			* 2 bytes for the length of this attribute: 0x0008 (= 8 bytes)
			* 2 bytes for permissions: 0x010a (= read, write, dynamic)
			* 2 bytes for the handle of this attribute
			* 2 bytes for the 16-bit short UUID that indicates a user description attribute: 0x2901

	==== The BTstack runloop ====		==== The BTstack runloop ====

Kai: BTstack Python output for a GATT user description declaration attribute

2025-05-09T19:24:53Z

BTstack Python output for a GATT user description declaration attribute

← Older revision		Revision as of 2025-05-09T19:24:53
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	* DYNAMIC: Indicates that reading and writing to this characteristic requires adding this case to the read and write callbacks.		* DYNAMIC: Indicates that reading and writing to this characteristic requires adding this case to the read and write callbacks.

	===== BTStack Python script output for a GATT characteristic declaration =====		===== BTStack Python script output for a GATT characteristic declaration attribute =====

	Let's have a look at the output of the BTstack Python script that converts the .gatt file to a C header and let's narrow it down to just the characteristic declarations.		Let's have a look at the output of the BTstack Python script that converts the .gatt file to a C header and let's narrow it down to just the characteristic declarations.
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	\|-		\|-
	\|}		\|}

			===== BTStack Python script output for a GATT user description declaration attribute =====

			<pre>
			0x08, 0x00, 0x0a, 0x01, 0x0a, 0x00, 0x01, 0x29,
			</pre>

	==== The BTstack runloop ====		==== The BTstack runloop ====

Kai: /* BTStack Python script output for different attribute permission combinations */

2025-05-09T19:22:36Z

BTStack Python script output for different attribute permission combinations

← Older revision		Revision as of 2025-05-09T19:22:36
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	* DYNAMIC: Indicates that reading and writing to this characteristic requires adding this case to the read and write callbacks.		* DYNAMIC: Indicates that reading and writing to this characteristic requires adding this case to the read and write callbacks.

	===== BTStack Python script output for ~~different attribute permission combinations~~ =====		===== BTStack Python script output for a GATT characteristic declaration =====

	Let's have a look at the output of the BTstack Python script that converts the .gatt file to a C header and let's narrow it down to just the characteristic declarations.		Let's have a look at the output of the BTstack Python script that converts the .gatt file to a C header and let's narrow it down to just the characteristic declarations.

Kai: Expanding on the GATT attribute that declares a characteristic

2025-05-09T19:18:57Z

Expanding on the GATT attribute that declares a characteristic

@@ Line 123: / Line 123: @@
 * WRITE_WITH_RESPONSE
 * NOTIFY: Adds a ''Client Configuration'' descriptor to the characteristic that allows a GATT client to control whether a notification is to be sent to the client each time the value of the characteristic changes.
-* DYNAMIC
+* DYNAMIC: Indicates that reading and writing to this characteristic requires adding this case to the read and write callbacks.
 ==== The BTstack runloop ====

Kai: Adding information about BLE GATT tables and BTstack's GATT files.

2025-05-08T21:19:15Z

Adding information about BLE GATT tables and BTstack's GATT files.

@@ Line 111: / Line 111: @@
 #endif // MY_BTSTACK_CONFIG_H
 </syntaxhighlight>
 ==== The BTstack runloop ====

Kai: /* Setup */

2025-05-08T08:44:53Z

Setup

← Older revision		Revision as of 2025-05-08T08:44:53
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	#endif		#endif

			// logging
	#define ENABLE_LOG_INFO		#define ENABLE_LOG_INFO
	#define ENABLE_LOG_ERROR		#define ENABLE_LOG_ERROR
			#define ENABLE_PRINTF_HEXDUMP // required for hci_dump_init()

	#if 1 // configure as peripheral (GATT server)		#if 1 // configure as peripheral (GATT server)
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	#define MAX_NR_WHITELIST_ENTRIES 16		#define MAX_NR_WHITELIST_ENTRIES 16
	#define MAX_NR_LE_DEVICE_DB_ENTRIES 16		#define MAX_NR_LE_DEVICE_DB_ENTRIES 16

	~~#define ENABLE_PRINTF_HEXDUMP~~

	// Choosing a fixed-size attributes table over using malloc.		// Choosing a fixed-size attributes table over using malloc.