Hi,
I could use some help understanding and hopefully fixing a BLE Midi problem.
I have bought a new MIDI device (Roland GO:Keys). This device connects
fine via BLE, but does not send any key events. I have another keyboard
working fine via BLE. Both devices work with android.
After digging into code and specs, I think that the chain of events is:
- The MIDI Service is found
- The characteristics are parsed
- The code thinks that all characteristics in the PDU have 16bit UUIDS
(len 7), while 3 of them. are 128bit
- Thus it parses nonsense, and does not find the Midi I/O
characteristic, no data transfer possible.
src/device.c:gatt_debug() MTU exchange complete, with MTU: 96
src/device.c:gatt_debug() Primary services found: 4
src/device.c:gatt_debug() start: 0x0001, end: 0x0003, uuid:
00001800-0000-1000-8000-00805f9b34fb
src/device.c:gatt_debug() start: 0x0007, end: 0x000f, uuid:
03b80e5a-ede8-4b33-a751-6ce34ec4c700
src/device.c:gatt_debug() start: 0x0021, end: 0x0023, uuid:
00001801-0000-1000-8000-00805f9b34fb
src/device.c:gatt_debug() start: 0x0031, end: 0x0041, uuid:
0000180a-0000-1000-8000-00805f9b34fb
src/device.c:gatt_debug() Characteristics found: 19
src/device.c:gatt_debug() start: 0x0002, end: 0x0007, value: 0x0003,
props: 0x0a, uuid: 00002a00-0000-1
src/device.c:gatt_debug() start: 0x0008, end: 0x28a5, value: 0x0009,
props: 0x18, uuid: 00000318-0000-1
src/device.c:gatt_debug() start: 0x28a6, end: 0xa347, value: 0xecd8,
props: 0x5e, uuid: 00001c91-0000-1
src/device.c:gatt_debug() start: 0xa348, end: 0x000a, value: 0x5343,
props: 0xac, uuid: 00004953-0000-1
src/device.c:gatt_debug() start: 0x000b, end: 0x9d0f, value: 0x000c,
props: 0x1e, uuid: 00006bf3-0000-1
src/device.c:gatt_debug() start: 0x9d10, end: 0x6840, value: 0xa9f2,
props: 0x66, uuid: 000012a1-0000-1
...
From parsing handle 8, he parses 3 16 bit UUIDs instead of one 128bit.
wireshark has the same problem and misparses the buffer.
The buffer is the result of a
ATT_OP_READ_BY_TYPE_RESP opcode, which contains a unit length for the
whole buffer, which is correct for some, but no all characteristics in
the PDU.
Comparing the attributs from my working with my not working device, I find:
- The not working ROLAND has a total of 3 characteristics with 128bit
UUIDS for the MIDI Service, the one needed ist the second one.
- The device also contains an audio sink, which I think does not matter
Now for the things that I don't know and where I could use some help:
- Bug in the bluez stack or should I write to Roland?
- I have no idea why my other MIDI Device works, mixed 16bit and
128bit UUIDS is needed in both cases
- How can I make sure that an attribute response only contains UUIDs
of one kind? That seems to be required, since there is only one 'len'
element.
- Any tips on what needs to be changed?
Also attached is a wireshark dissection and hexdump of the "Read by Type
Response":
I have a very ugly workaround, but having spent way to much time on
debugging this, I could also invest the work for a proper patch.
Thanks,
Jo
--
Johannes Deisenhofer
Frame 1034: 20 bytes on wire (160 bits), 20 bytes captured (160 bits) on interface bluetooth-monitor, id 0
Bluetooth
Bluetooth Linux Monitor Transport
Bluetooth HCI ACL Packet
Bluetooth L2CAP Protocol
Bluetooth Attribute Protocol
Opcode: Read By Type Response (0x09)
Length: 7
Attribute Data, Handle: 0x0002, Characteristic Handle: 0x0003, UUID: Device Name
Handle: 0x0002 (Generic Access Profile: GATT Characteristic Declaration)
[Service UUID: Generic Access Profile (0x1800)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0x0a, Write, Read
Characteristic Value Handle: 0x0003 (Generic Access Profile: Device Name)
[Service UUID: Generic Access Profile (0x1800)]
[UUID: Device Name (0x2a00)]
UUID: Device Name (0x2a00)
Attribute Data, Handle: 0x0008, Characteristic Handle: 0x0009, UUID: Unknown
Handle: 0x0008 (Unknown: GATT Characteristic Declaration)
[Service UUID: 03b80e5aede84b33a7516ce34ec4c700]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0x18, Notify, Write
Characteristic Value Handle: 0x0009 (Unknown: Unknown)
[Service UUID: 03b80e5aede84b33a7516ce34ec4c700]
[UUID: Unknown (0x0318)]
UUID: Unknown (0x0318)
Attribute Data, Handle: 0x28a6, Characteristic Handle: 0xecd8, UUID: Unknown
Handle: 0x28a6 (Device Information: Model Number String: GATT Characteristic Declaration)
[Service UUID: Device Information (0x180a)]
[Characteristic UUID: Model Number String (0x2a24)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0x5e, Authenticated Signed Writes, Notify, Write, Write without Response, Read
Characteristic Value Handle: 0xecd8 (Device Information: Unknown)
[Service UUID: Device Information (0x180a)]
[UUID: Unknown (0x1c91)]
UUID: Unknown (0x1c91)
Attribute Data, Handle: 0xa348, Characteristic Handle: 0x5343, UUID: Unknown
Handle: 0xa348 (Device Information: Unknown: GATT Characteristic Declaration)
[Service UUID: Device Information (0x180a)]
[Characteristic UUID: Unknown (0x4953)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0xac, Extended Properties, Indicate, Write, Write without Response
Characteristic Value Handle: 0x5343 (Device Information: Unknown)
[Service UUID: Device Information (0x180a)]
[UUID: Unknown (0x4953)]
UUID: Unknown (0x4953)
Attribute Data, Handle: 0x000b, Characteristic Handle: 0x000c, UUID: Unknown
Handle: 0x000b (Unknown: Unknown: GATT Characteristic Declaration)
[Service UUID: 03b80e5aede84b33a7516ce34ec4c700]
[Characteristic UUID: Unknown (0x0318)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0x1e, Notify, Write, Write without Response, Read
Characteristic Value Handle: 0x000c (Unknown: Unknown)
[Service UUID: 03b80e5aede84b33a7516ce34ec4c700]
[UUID: Unknown (0x6bf3)]
UUID: Unknown (0x6bf3)
Attribute Data, Handle: 0x9d10, Characteristic Handle: 0xa9f2, UUID: Unknown
Handle: 0x9d10 (Device Information: Unknown: GATT Characteristic Declaration)
[Service UUID: Device Information (0x180a)]
[Characteristic UUID: Unknown (0x4953)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0x66, Authenticated Signed Writes, Indicate, Write without Response, Read
Characteristic Value Handle: 0xa9f2 (Device Information: Unknown)
[Service UUID: Device Information (0x180a)]
[UUID: Unknown (0x12a1)]
UUID: Unknown (0x12a1)
Attribute Data, Handle: 0x6841, Characteristic Handle: 0xe5db, UUID: Unknown
Handle: 0x6841 (Device Information: Unknown: GATT Characteristic Declaration)
[Service UUID: Device Information (0x180a)]
[Characteristic UUID: Unknown (0x4953)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0x38, Indicate, Notify, Write
Characteristic Value Handle: 0xe5db (Device Information: Unknown)
[Service UUID: Device Information (0x180a)]
[UUID: Unknown (0x7772)]
UUID: Unknown (0x7772)
Attribute Data, Handle: 0x000e, Characteristic Handle: 0x000f, UUID: Unknown
Handle: 0x000e (Unknown: Unknown: GATT Characteristic Declaration)
[Service UUID: 03b80e5aede84b33a7516ce34ec4c700]
[Characteristic UUID: Unknown (0x6bf3)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0x08, Write
Characteristic Value Handle: 0x000f (Unknown: Unknown)
[Service UUID: 03b80e5aede84b33a7516ce34ec4c700]
[UUID: Unknown (0x9bb3)]
UUID: Unknown (0x9bb3)
Attribute Data, Handle: 0x3472, Characteristic Handle: 0xd4ec, UUID: Unknown
Handle: 0x3472 (Device Information: Model Number String: GATT Characteristic Declaration)
[Service UUID: Device Information (0x180a)]
[Characteristic UUID: Model Number String (0x2a24)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0xbe, Extended Properties, Indicate, Notify, Write, Write without Response, Read
Characteristic Value Handle: 0xd4ec (Device Information: Unknown)
[Service UUID: Device Information (0x180a)]
[UUID: Unknown (0xf4a8)]
UUID: Unknown (0xf4a8)
Attribute Data, Handle: 0x4143, Characteristic Handle: 0x5343, UUID: Unknown
Handle: 0x4143 (Device Information: Model Number String: GATT Characteristic Declaration)
[Service UUID: Device Information (0x180a)]
[Characteristic UUID: Model Number String (0x2a24)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0x88, Extended Properties, Write
Characteristic Value Handle: 0x5343 (Device Information: Unknown)
[Service UUID: Device Information (0x180a)]
[UUID: Unknown (0x4953)]
UUID: Unknown (0x4953)
Attribute Data, Handle: 0x0022, Characteristic Handle: 0x0023, UUID: Service Changed
Handle: 0x0022 (Generic Attribute Profile: GATT Characteristic Declaration)
[Service UUID: Generic Attribute Profile (0x1801)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0x26, Indicate, Write without Response, Read
Characteristic Value Handle: 0x0023 (Generic Attribute Profile: Service Changed)
[Service UUID: Generic Attribute Profile (0x1801)]
[UUID: Service Changed (0x2a05)]
UUID: Service Changed (0x2a05)
Attribute Data, Handle: 0x0032, Characteristic Handle: 0x0033, UUID: Manufacturer Name String
Handle: 0x0032 (Device Information: GATT Characteristic Declaration)
[Service UUID: Device Information (0x180a)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0x02, Read
Characteristic Value Handle: 0x0033 (Device Information: Manufacturer Name String)
[Service UUID: Device Information (0x180a)]
[UUID: Manufacturer Name String (0x2a29)]
UUID: Manufacturer Name String (0x2a29)
Attribute Data, Handle: 0x0034, Characteristic Handle: 0x0035, UUID: Model Number String
Handle: 0x0034 (Device Information: Manufacturer Name String: GATT Characteristic Declaration)
[Service UUID: Device Information (0x180a)]
[Characteristic UUID: Manufacturer Name String (0x2a29)]
[UUID: GATT Characteristic Declaration (0x2803)]
Characteristic Properties: 0x02, Read
Characteristic Value Handle: 0x0035 (Device Information: Model Number String)
[Service UUID: Device Information (0x180a)]
[UUID: Model Number String (0x2a24)]
UUID: Model Number String (0x2a24)
[UUID: GATT Characteristic Declaration (0x2803)]
[Request in Frame: 1028]
0000 5d 00 04 00 09 07 02 00 0a 03 00 00 2a 08 00 18 ]...........*...
0010 09 00 18 03 a6 28 5e d8 ec 91 1c 48 a3 ac 43 53 .....(^....H..CS
0020 53 49 0b 00 1e 0c 00 f3 6b 10 9d 66 f2 a9 a1 12 SI......k..f....
0030 41 68 38 db e5 72 77 0e 00 08 0f 00 b3 9b 72 34 Ah8..rw.......r4
0040 be ec d4 a8 f4 43 41 88 43 53 53 49 22 00 26 23 .....CA.CSSI".&#
0050 00 05 2a 32 00 02 33 00 29 2a 34 00 02 35 00 24 ..*2..3.)*4..5.$
0060 2a *
