This is a guide to the Symbian platform Bluetooth implementation of Extended Inquiry Response (EIR).
EIR provides information about discoverable devices during a Bluetooth Inquiry.
Intended audience:
This document is intended to be used by Symbian platform licensees and third party application developers.
A Bluetooth communication connection is created by two or more devices within a piconet. A device that wishes to create a connection must find which other devices/services are available. The Inquiry is a request sent by a Bluetooth-enabled device (the "Inquiring Device") over a separate physical channel, not within an existing piconet. The Inquiry requests all listening ("discoverable") Bluetooth devices to identify themselves. In the standard Inquiry Response each device responds with their own MAC identifier. The Inquiring Device then has to issue a request to each device to determine the local name and any services that each device can support. Supported services may include stereo headset or FTP.
The Extended Inquiry Response (EIR) replaces the standard Inquiry Response and contains additional information.
Legacy devices are supported so the set of responses from all devices may include both EIR and standard Inquiry Responses.
The Extended Inquiry Response includes the following:
device local name
service class UUIDs of each service the device supports
the transmission power
manufacturer specific values
Device local name
On a device such as a phone handset the device local name may be set by the user. For example, "Tom's Nokia E71". Otherwise the local name defined by the manufacturer, for example "MyTech BT Headset". The EIR data packet is a fixed size so the number of characters available for the device local name may be insufficient for the entire device local name. The data sent is as many characters as fit starting with the first character. The number of characters available depends on how many service IDs are sent and so this length varies from device to device. A flag is available to indicate whether the device local name sent is the complete name or a truncated version.
Service class UUIDs of each service the device supports
A Service Class UUID is a value which identifies a particular type of service/functionality provided by the device. For example, there would be a Service Class UUID to identify a printer, and another Service Class UUID to identify a stereo headset.
Transmission Power
A one byte value containing a transmission power level between -127dBm and +127dBm. The Transmission Power (Tx Power) value is optional. May be used in conjunction with the Received Signal Strength Indicator (RSSI) to calculate pathloss and give an estimate of which of two or more responding devices is physically closer to the Inquiring Device.
Manufacturer specific values
This is a set of 8-bit bytes and all interpretation and structure is entirely down to the specific manufacturer.