Why don't I get a BLE_GATTS_EVT_SYS_ATTR_MISSING event?

[brianreinhold]

This discussion got mixed up with a discussion about what Nordic means by a 'system attribute' (which is still not clear). In any case, in that discussion I was trying to save pairing/bonding information so I could restore it on a reconnect. The pairing keys worked. I grabbed the keys on the pairing complete event, saved them to a file, read them from that file, and gave them to the peer when asked on a reconnect in the BLE_GAP_EVT_SEC_INFO_REQUEST event.

But the CCCD information doesn't work that way. I can't restore the CCCD state using the same approach, because I cannot initialize the CCCD myself from the application (even prior to a connection). Instead I was told I need to get the 'system attributes' by calling this method sd_ble_gatts_sys_attr_get(), save them to a file, and restore them by calling this method sd_ble_gatts_sys_attr_set() when I get a BLE_GATTS_EVT_SYS_ATTR_MISSING event.

Fantastic! Sounds easy enough. However, I never get a BLE_GATTS_EVT_SYS_ATTR_MISSING event. I get this event BLE_GAP_EVT_SEC_INFO_REQUEST to restore the keys, so that works. What is missing?

[tesc]

Hi,

Sorry for the delay, I thought you were going to provide the project, but now I realize you asked how to do so.

If you do not want to attach it here in this public thread, you can create a private ticket, attach it there, and refer to this thread from the private ticket.

Regards,
Terje

[brianreinhold]

I do not SEE a way to attach the project or anything else.

[tesc]

Hi,

You can attach files to a reply here in this thread. From the "Insert" menu you can "Insert image/video/file", which lets you attach any type of file.

You can also attach files to the opening post of a new thread, both for public and private threads.

Regards,
Terje

[brianreinhold]

I was in Amsterdam last week at an HL7 FHIR Dev Days meeting and did not have access to this project. Sorry about the delay.

I will try to attach the project.

I have set up the code to do the following in 3 stages

Stage 1:

Starts advertising as a heart rate monitor; supports a DIS, and requires pairing before one can enable notifications on the measurement characteristic.

Once connected, the usual spin-up. Pairing will happen when the client tries to enable notifications

It sends a few measurements then disconnects

Stage 2:

Re-run the same setup.

Start advertising again. 

Once connected It sends the measurements (the client re-enables notifications but that is so because there are too many devices in the field which do not support bonding correctly).

Disconnects.

Stage 3

Reconfigures the device to have no DIS and changes some of the fields in the HR characteristic

Configures the device to invoke service changed on connection event.

start advertising

once connected, service changed  fails.

HERE IS THE LOG of that sequence:

Serial port used: COM5
Baud rate used: 1000000
Info: Successfully opened COM5. Baud rate: 1000000. Flow control: none. Parity: none.
Status: 6, message: Target Reset performed
Status: 7, message: Connection active
Advertising data set
Service initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Service initiated
Characteristic initiated
Characteristic initiated
Started advertising at time 0
Connected at time 641, connection handle 0x0001
Result of sending encryption params 0
Security settings reported at time 1282:
security level: 2
security mode: 1
key length: 16
Read write authorized request signaled
Read authorized request at time 1422 for characteristic 2A23
Read update reply response 0
Read write authorized request signaled
Read authorized request at time 1625 for characteristic 2A26
Read update reply response 0
Read write authorized request signaled
Read authorized request at time 1813 for characteristic 2A28
Read update reply response 0
Read write authorized request signaled
Read authorized request at time 2016 for characteristic 2A27
Read update reply response 0
Read write authorized request signaled
Read authorized request at time 2203 for characteristic 2A29
Read update reply response 0
Read write authorized request signaled
Read authorized request at time 2407 for characteristic 2A25
Read update reply response 0
Client Enabling CCCD of characeteristic handle 13 with value 2 at time 2500
Read write authorized request signaled
Read authorized request at time 2594 for characteristic 2A24
Read update reply response 0
Read write authorized request signaled
Read authorized request at time 2688 for characteristic 2A2A
Read update reply response 0
Read write authorized request signaled
Read authorized request at time 2797 for characteristic 2A2A
Read update reply response 0
Enabling CCCD with 1 at time 2891
Send mesurement 40
Successfully transmitted a heart rate reading.
Send mesurement 43
Successfully transmitted a heart rate reading.
Send mesurement 46
Successfully transmitted a heart rate reading.
Send mesurement 49
Successfully transmitted a heart rate reading.
Disconnected at time 6985
Info: serial port COM5 closed.
Saving data to file at time 7922
Closed at time 7938

Serial port used: COM5
Baud rate used: 1000000
Info: Successfully opened COM5. Baud rate: 1000000. Flow control: none. Parity: none.
Status: 6, message: Target Reset performed
Status: 7, message: Connection active
Advertising data set
Service initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Characteristic initiated
Service initiated
Characteristic initiated
Characteristic initiated
Started advertising at time 0
Connected at time 563, connection handle 0x0001
Result of sending encryption params 0
Security settings reported at time 1094:
security level: 2
security mode: 1
key length: 16
Enabling CCCD with 1 at time 1235
Send mesurement 40
Successfully transmitted a heart rate reading.
Client Enabling CCCD of characeteristic handle 13 with value 2 at time 1875
Send mesurement 43
Successfully transmitted a heart rate reading.
Send mesurement 46
Successfully transmitted a heart rate reading.
Send mesurement 49
Successfully transmitted a heart rate reading.
Disconnected at time 5328
Info: serial port COM5 closed.
Saving data to file at time 6282
Closed at time 6282

Serial port used: COM5
Baud rate used: 1000000
Info: Successfully opened COM5. Baud rate: 1000000. Flow control: none. Parity: none.
Status: 6, message: Target Reset performed
Status: 7, message: Connection active
Advertising data set
Service initiated
Characteristic initiated
Characteristic initiated
Started advertising at time 0
Connected at time 281, connection handle 0x0001
Failed invoking service changed indication. Invalid handle 0
Failed invoking service changed indication. Invalid handle 1
Failed invoking service changed indication. Invalid handle 2
Failed invoking service changed indication. Invalid handle 3
Failed invoking service changed indication. Invalid handle 4
Failed invoking service changed indication. Invalid handle 5
Failed invoking service changed indication. Invalid handle 6
Failed invoking service changed indication. Invalid handle 7
Failed invoking service changed indication. Invalid handle 8
Failed invoking service changed indication. Invalid handle 9
Failed invoking service changed indication. Invalid handle 10
Failed invoking service changed indication. Invalid handle 11
Failed invoking service changed indication. Invalid handle 12
Failed invoking service changed indication. Invalid handle 13
Failed invoking service changed indication. Service attributes missing
Result of sending encryption params 0
Security settings reported at time 984:
security level: 2
security mode: 1
key length: 16
Disconnected at time 1281
Info: serial port COM5 closed.
Saving data to file at time 1297
Closed at time 1297

Attached is the Visual Studio 2019 community edition project.

Using nRF52840 dongle

The client application is a production Android Personal Health Gateway used in the field for health devices (HDP, SPP, and BTLE)in remote patient monitoring scenarios (Health@Home PHG on Android Playstore - free). I may need to give you an APK that is preconfigured with a fake patient.. That is needed to run the application. You can configure it yourself but that can be confusing.

If you have a client app that supports the above that should work as well. Looks like the attachment worked!

BleHeartRateMonitor.zip

[brianreinhold]

I need to add that this web site implementation has serious issues. I just posted something and I cannot edit it because the buttons at the bottom do not show up. This happens frequently. Sometimes a page refresh works or clicking on a reply button to another message where the buttons ARE visible, or existing and resigning in.

Adding this extra reply made the buttons at the bottom of the 'real' message re-appear.