We have an NRF52 set up as Central, connecting to a peripheral (not our own) that's sending notifications with Data>20 bytes
I'm trying to differentiate between it sending two seperate sets of bytes 20 then 10, or a single set of 30 bytes, as an example.
I was hoping to use params.offset, but this is only available for writes and reads, not for receiving notifications. (from a quick look through devzone, it does appear to be available when sending a notification as a peripheral though?).
Before digging further into this only to possibly find out that the peripheral is not even sending an offset, I sniffed the communication, as attached.
The interesting difference I see is the "More Data" bit in the Data header
Data Header: 0x1b16
.... ..10 = LLID: Start of an L2CAP message or a complete L2CAP message with no fragmentation (0x2)
.... .1.. = Next Expected Sequence Number: 1
.... 0... = Sequence Number: 0 [OK]
...1 .... = More Data: True
000. .... = RFU: 0
vs
Data Header: 0x110a
.... ..10 = LLID: Start of an L2CAP message or a complete L2CAP message with no fragmentation (0x2)
.... .0.. = Next Expected Sequence Number: 0
.... 1... = Sequence Number: 1 [OK]
...0 .... = More Data: False
000. .... = RFU: 0
how can I access that info (or any derivation of that info), so that if there is more to come, I buffer the first notification, and wait for the rest of the data in the next notification before further processing it?
p_ble_evt->evt.gattc_evt.params.hvx only contains data, handle, len and type - none of which reflects the More Data info.
Thanks already!
No. Time Source PHY Protocol Length Delta time (µs end to start) SN NESN More Data Event counter Info
363 12.471 Slave_0x1376ef35 LE 1M ATT 27 151 0 1 True 151 Rcvd Handle Value Notification, Handle: 0x0017 (Unknown: Unknown)
Frame 363: 53 bytes on wire (424 bits), 53 bytes captured (424 bits) on interface 0
Nordic BLE Sniffer
Bluetooth Low Energy Link Layer
Access Address: 0x1376ef35
[Master Address: XX:XX:XX:XX:XX:XX (XX:XX:XX:XX:XX:XX)]
[Slave Address: XX:XX:XX:XX:XX:XX (XX:XX:XX:XX:XX:XX)]
Data Header: 0x1b16
.... ..10 = LLID: Start of an L2CAP message or a complete L2CAP message with no fragmentation (0x2)
.... .1.. = Next Expected Sequence Number: 1
.... 0... = Sequence Number: 0 [OK]
...1 .... = More Data: True
000. .... = RFU: 0
Length: 27
[L2CAP Index: 33]
CRC: 0x1606b1
Bluetooth L2CAP Protocol
Length: 23
CID: Attribute Protocol (0x0004)
Bluetooth Attribute Protocol
Opcode: Handle Value Notification (0x1b)
0... .... = Authentication Signature: False
.0.. .... = Command: False
..01 1011 = Method: Handle Value Notification (0x1b)
Handle: 0x0017 (Unknown)
[UUID: 720330f41db74fd7ae5a87e5bd942880]
Value: 3132333435363738393031323334353637383930
No. Time Source PHY Protocol Length Delta time (µs end to start) SN NESN More Data Event counter Info
365 12.473 Slave_0x1376ef35 LE 1M ATT 17 151 1 0 False 151 Rcvd Handle Value Notification, Handle: 0x0017 (Unknown: Unknown)
Frame 365: 43 bytes on wire (344 bits), 43 bytes captured (344 bits) on interface 0
Nordic BLE Sniffer
Bluetooth Low Energy Link Layer
Access Address: 0x1376ef35
[Master Address: XX:XX:XX:XX:XX:XX (XX:XX:XX:XX:XX:XX)]
[Slave Address: XX:XX:XX:XX:XX:XX (XX:XX:XX:XX:XX:XX)]
Data Header: 0x110a
.... ..10 = LLID: Start of an L2CAP message or a complete L2CAP message with no fragmentation (0x2)
.... .0.. = Next Expected Sequence Number: 0
.... 1... = Sequence Number: 1 [OK]
...0 .... = More Data: False
000. .... = RFU: 0
Length: 17
[L2CAP Index: 34]
CRC: 0x627f49
Bluetooth L2CAP Protocol
Length: 13
CID: Attribute Protocol (0x0004)
Bluetooth Attribute Protocol
Opcode: Handle Value Notification (0x1b)
0... .... = Authentication Signature: False
.0.. .... = Command: False
..01 1011 = Method: Handle Value Notification (0x1b)
Handle: 0x0017 (Unknown)
[UUID: 720330f41db74fd7ae5a87e5bd942880]
Value: 3132333435363738390d
[EDIT:] I know I could wait for the 0x0d at the end if I'm expecting that, but that's not guaranteed to be sent, so I can't rely on it.
