building a bt 4.0 le hid device
TRANSCRIPT
London Bluetooth Hardware Developers
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Venue
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“Apple iBeacon Technology Overview”Vladimir Petrov @VladPetroff
🍕🍩🍻💬 🍕🍩🍻💬 🍕🍩🍻💬
“Deploying beacons in a retail environment” Tim Woolford @tim_woolford
“Introduction to Avnet and Bluegiga BLE121LR” Alastair Worth @wirelessworthy
🍻 Blueberry Bar, across the road
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“Building a BT 4.0 LE HID device” Nick Brook @nrbrook
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“Building a BT 4.0 LE HID device”Nick Brook @nrbrook
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• Bluetooth foot pedal
• Supports up to 4 pedals
• Used primarily with music display Apps, turning pages
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AirTurn BT-105
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• Bluetooth 2.1
• HID device — Bluetooth keyboard
• iOS
• Doesn’t provide access to key events (directly, <7)
• Hides the virtual keyboard
• Requires hacks
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AirTurn BT-105
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• Provides direct access to Bluetooth 4 LE devices
• Introduced iOS 5
• Good device support
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CoreBluetooth
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• AKA “Bluetooth Smart”
• Entirely new protocol stack (vs Bluetooth “Classic”)
• Peripheral (Server) advertises services
• Central (Client) scans and connects to devices
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Bluetooth 4 LE
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Bluetooth 4 LE
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• 31 byte advertising packet + scan response
• GATT Database
• Services
• Characteristics (key -> value store)
• Up to 512 bytes
• Read, write, notify
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Bluetooth 4 LE
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• Some services defined by Bluetooth SIG, e.g.
• Human Interface Device
• Device Information
• Battery
• You can define your own services
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Bluetooth 4 LE
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• Simple
• Quick to learn
• Can achieve a lot
• Some oddities
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Bluetooth 4 LE
Protocol Requirements 30 June 2010
BLUETOOTH SPECIFICATION Version 4.0 [Vol 3] page 485 of 656
Attribute Protocol (ATT)
If an error code is received in the Error Response that is not understood by the client, for example an error code that was reserved for future use that is now being used in a future version of this specification, then the Error Response shall still be considered to state that the given request cannot be performed for an unknown reason.
3.4.2 MTU Exchange
3.4.2.1 Exchange MTU Request
The Exchange MTU Request is used by the client to inform the server of the client’s maximum receive MTU size and request the server to respond with its maximum receive MTU size.
The Client Rx MTU shall be greater than or equal to the default ATT_MTU.
This request shall only be sent once during a connection by the client. The Cli-ent Rx MTU parameter shall be set to the maximum size of the attribute proto-col PDU that the client can receive.
Unlikely Error 0x0E The attribute request that was requested has encountered an error that was unlikely, and therefore could not be completed as requested.
Insufficient Encryption 0x0F The attribute requires encryption before it can be read or written.
Unsupported Group Type 0x10 The attribute type is not a supported grouping attribute as defined by a higher layer specification.
Insufficient Resources 0x11 Insufficient Resources to complete the request
Reserved 0x012 – 0x7F Reserved for future use.
Application Error 0x80 – 0xFF Application error code defined by a higher layer specification.
Parameter Size (octets) Description
Attribute Opcode 1 0x02 = Exchange MTU Request
Client Rx MTU 2 Client receive MTU size
Table 3.4: Format of Exchange MTU Request
Name Error Code Description
Table 3.3: Error Codes
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• Small
• Low cost (£8)
• Low power (CR2032)
• Complete integrated package (radio, antenna, microcontroller, flash, GPIO, UART, I2C, PWM, ADC)
• Easy, simple, quick to get started
• BGScript
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Bluegiga BLE113
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• Don’t need much circuitry around the package
• Power supply
• Any sensors/IO
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Bluegiga BLE113
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Profile Toolkit
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BGScript
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• Custom GATT service
• Provides pedal state change notifications
• Also supports HID for keyboard / mouse commands
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New AirTurn
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• Scans for / connects to devices
• UI provided
• Sends out notifications on pedal events
• Works in background
• Different AirTurns connected to different Apps
• Simple to implement
• No Hacks!!
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New framework
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• Growing number of freelance projects
• Get in touch
• @nrbrook
• Speak to me!
• Please give feedback! http://goo.gl/HgSrgu
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LE + mobile projects