BLE en Raspberry Pi

Posted on 2 febrero, 2018

Como hemos visto en una entrada anterior la Raspberry Pi 3 dispone de BLE.

Para comenzar a trabajar con BLE en Raspberry Pi debemos comprobar que está disponible, mediante el comando hciconfig:

pi@raspberrypi:~ $ hciconfig
hci0: Type: Primary Bus: UART
 BD Address: XX:XX:XX:XX:XX:XX ACL MTU: 1021:8 SCO MTU: 64:1
 UP RUNNING 
 RX bytes:822 acl:0 sco:0 events:57 errors:0
 TX bytes:4231 acl:0 sco:0 commands:57 errors:0

En caso de que no esté arrancado hay que activarlo

sudo hciconfig hci0 up

Una utilidad que proporciona más información es blescan

pi@raspberrypi:~ $ sudo blescan
Scanning for devices...
Device (new): xx:xx:xx:xx:xx:xx (random), -91 dBm (not connectable)
Manufacturer: <060001092000c7ce0663439d1e190d97c0a7827dfe0cb225c5cad35fee>

Después de comprobar que BLE está activado podemos arrancar el modo central u observador que escucha en las direcciones más usuales y nos devuelve las direcciones MAC (Se han cambiado el resultado de las MAC, son identificaciones únicas a nivel globalpor XX:XX:XX:XX:XX:XX):

pi@raspberrypi:~ $ sudo hcitool lescan
LE Scan ...
XX:XX:XX:XX:XX:XX (unknown)
XX:XX:XX:XX:XX:XX (unknown)
XX:XX:XX:XX:XX:XX (unknown)
XX:XX:XX:XX:XX:XX Flex
XX:XX:XX:XX:XX:XX (unknown)
XX:XX:XX:XX:XX:XX MTLocomotive

Una vez descubiertos los dispositivos BLE que están emitiendo anuncios o «beacons» podemos con la utilidad gatttool establecer una conexión:

pi@raspberrypi:~ $ gatttool -I -b XX:XX:XX:XX:XX:XX
[XX:XX:XX:XX:XX:XX][LE]>
[XX:XX:XX:XX:XX:XX][LE]> connect
Attempting to connect to XX:XX:XX:XX:XX:XX 
Error: connect error: Connection refused (111)

En este caso Flex se rechaza la conexión pues precisa una autentificación, los parámetros completos de gatttool son:

[XX:XX:XX:XX:XX:XX][LE]> help
help Show this help
exit Exit interactive mode
quit Exit interactive mode
connect [address [address type]] Connect to a remote device
disconnect Disconnect from a remote device
primary [UUID] Primary Service Discovery
included [start hnd [end hnd]] Find Included Services
characteristics [start hnd [end hnd [UUID]]] Characteristics Discovery
char-desc [start hnd] [end hnd] Characteristics Descriptor Discovery
char-read-hnd <handle> Characteristics Value/Descriptor Read by handle
char-read-uuid <UUID> [start hnd] [end hnd] Characteristics Value/Descriptor Read by UUID
char-write-req <handle> <new value> Characteristic Value Write (Write Request)
char-write-cmd <handle> <new value> Characteristic Value Write (No response)
sec-level [low | medium | high] Set security level. Default: low
mtu <value> Exchange MTU for GATT/ATT

Otra utilidad es bluetoothctl:

pi@raspberrypi:~ $ bluetoothctl
 [NEW] Controller XX:XX:XX:XX:XX:XX raspberrypi [default]
 [NEW] Device XX:XX:XX:XX:XX:XX Flex
 [NEW] Device XX:XX:XX:XX:XX:XX MTLocomotive

Los comandos de bluetoolhctl los podemos listar con help:

[bluetooth]# help
 Available commands:
 list List available controllers
 show [ctrl] Controller information
 select Select default controller
 devices List available devices
 paired-devices List paired devices
 power <on/off> Set controller power
 pairable <on/off> Set controller pairable mode
 discoverable <on/off> Set controller discoverable mode
 agent <on/off/capability> Enable/disable agent with given capability
 default-agent Set agent as the default one
 advertise <on/off/type> Enable/disable advertising with given type
 set-advertise-uuids [uuid1 uuid2 ...] Set advertise uuids
 set-advertise-service [uuid][data=[xx xx ...] Set advertise service data
 set-advertise-manufacturer [id][data=[xx xx ...] Set advertise manufacturer data
 set-advertise-tx-power <on/off> Enable/disable TX power to be advertised
 set-scan-filter-uuids [uuid1 uuid2 ...] Set scan filter uuids
 set-scan-filter-rssi [rssi] Set scan filter rssi, and clears pathloss
 set-scan-filter-pathloss [pathloss] Set scan filter pathloss, and clears rssi
 set-scan-filter-transport [transport] Set scan filter transport
 set-scan-filter-clear Clears discovery filter.
 scan <on/off> Scan for devices
 info [dev] Device information
 pair [dev] Pair with device
 trust [dev] Trust device
 untrust [dev] Untrust device
 block [dev] Block device
 unblock [dev] Unblock device
 remove Remove device
 connect Connect device
 disconnect [dev] Disconnect device
 list-attributes [dev] List attributes
 set-alias Set device alias
 select-attribute Select attribute
 attribute-info [attribute] Select attribute
 read Read attribute value
 write <data=[xx xx ...]> Write attribute value
 notify <on/off> Notify attribute value
 register-profile Register profile to connect
 unregister-profile Unregister profile
 version Display version
 quit Quit program

Con esta utilidad podemos encender y apagar BLE:

[bluetooth]# power off
 Changing power off succeeded
 [CHG] Controller XX:XX:XX:XX:XX:XX Powered: no
 [CHG] Controller XX:XX:XX:XX:XX:XX Discovering: no
 [CHG] Controller XX:XX:XX:XX:XX:XX Class: 0x000000
 [bluetooth]# power on
 [CHG] Controller XX:XX:XX:XX:XX:XX Class: 0x6c0000
 Changing power on succeeded
 [CHG] Controller XX:XX:XX:XX:XX:XX Powered: yes
 

Como con gatttool se puede arrancar el modo scan con scan on o ver la versión

[bluetooth]# version
 Version 5.43
 info XX:XX:XX:XX:XX:XX

Y obtener información de un dispositivo en concreto

 [bluetooth]# info XX:XX:XX:XX:XX:XX
 Device XX:XX:XX:XX:XX:XX
 Name: MTLocomotive
 Alias: MTLocomotive
 Paired: no
 Trusted: no
 Blocked: no
 Connected: no
 LegacyPairing: no
 UUID: Vendor specific (XXXXXXXX-4a75-4c14-9ede-c8a5fb84f77b)
 
 [bluetooth]# info XX:XX:XX:XX:XX:XX
 Device XX:XX:XX:XX:XX:XX
 Name: Flex
 Alias: Flex
 Paired: no
 Trusted: no
 Blocked: no
 Connected: no
 LegacyPairing: no
 UUID: Vendor specific (XXXXXXXX-6e7d-4601-bda2-bffaa68956ba)
 ServiceData Key: 0000180a-0000-1000-8000-00805f9b34fb
 ServiceData Value: 0x07
 ServiceData Value: 0x04

Parear

[bluetooth]# pair XX:XX:XX:XX:XX:XX
 Attempting to pair with XX:XX:XX:XX:XX:XX
 [CHG] Device XX:XX:XX:XX:XX:XX Connected: yes
 [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 00001530-1212-efde-1523-785feabcd123
 [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 00001800-0000-1000-8000-00805f9b34fb
 [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 00001801-0000-1000-8000-00805f9b34fb
 [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 98241523-4a75-4c14-9ede-c8a5fb84f77b
 [CHG] Device XX:XX:XX:XX:XX:XX ServicesResolved: yes
 [CHG] Device XX:XX:XX:XX:XX:XX Paired: yes
 [NEW] Primary Service
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0008
 00001801-0000-1000-8000-00805f9b34fb
 Generic Attribute Profile
 [NEW] Characteristic
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0008/char0009
 00002a05-0000-1000-8000-00805f9b34fb
 Service Changed
 [NEW] Descriptor
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0008/char0009/desc000b
 00002902-0000-1000-8000-00805f9b34fb
 Client Characteristic Configuration
 [NEW] Primary Service
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service000c
 98241523-4a75-4c14-9ede-c8a5fb84f77b
 Vendor specific
 [NEW] Characteristic
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service000c/char000d
 98241525-4a75-4c14-9ede-c8a5fb84f77b
 Vendor specific
 [NEW] Characteristic
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service000c/char000f
 98241524-4a75-4c14-9ede-c8a5fb84f77b
 Vendor specific
 [NEW] Descriptor
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service000c/char000f/desc0011
 00002902-0000-1000-8000-00805f9b34fb
 Client Characteristic Configuration
 [NEW] Primary Service
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0012
 00001530-1212-efde-1523-785feabcd123
 Vendor specific
 [NEW] Characteristic
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0012/char0013
 00001532-1212-efde-1523-785feabcd123
 Vendor specific
 [NEW] Characteristic
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0012/char0015
 00001531-1212-efde-1523-785feabcd123
 Vendor specific
 [NEW] Descriptor
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0012/char0015/desc0017
 00002902-0000-1000-8000-00805f9b34fb
 Client Characteristic Configuration
 [NEW] Characteristic
 /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0012/char0018
 00001534-1212-efde-1523-785feabcd123
 Vendor specific
 Pairing successful
 [CHG] Device XX:XX:XX:XX:XX:XX Trusted: yes

En una próxima entrada veremos como programar funciones BLE en Phyton