disconnecting while operations are in progress never gives BLE_GAP_EVT_DISCONNECTED event

[Paul Bradford]

2020-01-24-092119EST-ProductStoppedGettingEventsFromNordicDK.txtImprivataTestNordicEventsNotReceived.zipCalls_to_pc_ble_driver.cpp0285.2020-02-24-TestProgramUploadedToNordicSupport.zipFeb25TestProgramUploadedToNordicSupport.zipImprivata_bgTestApp.zipbgSDKTestAppMay4.zip2020-05-05-035347-NordicDK_USB840M_200505_ClockInternal_2in1.hex.txt.txtbgSDKTestAppMay6.zipI’m developing an application based on pc-ble-driver to talk to an nRF52840-based dongle (from Fanstel).

I’m having trouble disconnecting cleanly when a connection has operations in progress.  For example, I call ‘sd_ble_gattc_write’, which returns NRF_SUCCESS, but I don’t receive event BLE_GATTC_EVT_WRITE_RSP (after waiting 60 seconds), so I decide to disconnect. When this happens, sd_ble_gap_disconnect returns NRF_SUCCESS, but I do not receive BLE_GAP_EVT_DISCONNECTED even after waiting 30 seconds. The connection supervision timeout is 4 seconds.  What could cause the disconnect to not generate any BLE_GAP_EVT_DISCONNECTED event?

What I’m trying to accomplish here: if a connection is not responsive, I want to end that connection, without disturbing other connections I have open.

Thanks,

Paul Bradford

[Paul Bradford]

I have created a test program that reproduces this problem: failure to receive events after a write or read request.  I have posted test program ImprivataTestNordicEventsNotReceived.zip and the main source file NordicTest-pc-ble-driver.cpp.   My intention is that you use the test program binaries, as described in the README.txt n the zip file. I included the source just so you can see what I'm doing, but I didn't include all headers to make it buildable.

[Jørgen Holmefjord]

Thanks for providing the example and detailed instructions. I have managed to run the test, and I have observed a few errors:

2020-02-05 17:18:11.814: sd_ble_gattc_read failed during characteristic_metadata_discovery_start error 0x0008 NRF_ERROR_INVALID_STATE, conn_handle = 0
2020-02-05 17:20:07.410: current GATTC read/write timed out
2020-02-05 17:20:07.410: sd_ble_gattc_read to keep connection alive got BLE_GATTC_EVT_TIMEOUT (which is allowable), so we must disconnect
2020-02-05 17:20:07.439: ERROR: sd_ble_gap_disconnect failed handle 0 error 0x3002 BLE_ERROR_INVALID_CONN_HANDLE
2020-02-05 17:20:43.446: current GATTC read/write timed out
2020-02-05 17:20:43.446: sd_ble_gattc_read to keep connection alive got BLE_GATTC_EVT_TIMEOUT (which is allowable), so we must disconnect
2020-02-05 17:20:43.507: ERROR: sd_ble_gap_disconnect failed handle 0 error 0x3002 BLE_ERROR_INVALID_CONN_HANDLE
2020-02-05 17:22:03.067: current GATTC read/write timed out
2020-02-05 17:22:03.067: sd_ble_gattc_write for characteristic notification got BLE_GATTC_EVT_TIMEOUT (which is allowable), so we must disconnect
2020-02-05 17:22:06.154: sd_ble_gattc_read failed during characteristic_metadata_discovery_start error 0x0008 NRF_ERROR_INVALID_STATE, conn_handle = 0
2020-02-05 17:22:39.167: current GATTC read/write timed out
2020-02-05 17:22:39.167: sd_ble_gattc_read to keep connection alive got BLE_GATTC_EVT_TIMEOUT (which is allowable), so we must disconnect
2020-02-05 17:22:39.254: ERROR: sd_ble_gap_disconnect failed handle 0 error 0x3002 BLE_ERROR_INVALID_CONN_HANDLE

I'm not sure if any of these are related to the issues you are seeing? How long does it normally take before the issue occurs with a single connection?

[Jørgen Holmefjord]

You can read about the SoftDevice Handler library in the SDK documentation. This is used by most examples in the SDK, to handle the interaction with the softdevice.

I have involved our SDK team, and they are currently investigating this issue. I will get back to you as soon as I receive more feedback from them.

[Jørgen Holmefjord]

Our developers are having some problems with reproducing this on their side. This is a bit strange since I'm able to reproduce within a few minutes every time I run the test with my test-phone. I will be working with them further on Monday to assure they have all the details on how the issue can be reproduced. Have a nice weekend!

[Jørgen Holmefjord]

The developer has managed to reproduce the issue, but have not found any root cause of the issue yet. I will be out of the office for the rest of the week, but my colleague will follow up on this thread if there are any updates.

[Paul Bradford]

Update on the two problems in this case:

1. I’ve found the cause of the error “never got BLE_GAP_EVT_CONNECTED or BLE_GAP_EVT_TIMEOUT(BLE_GAP_TIMEOUT_SRC_CONN)”.   ble_gap_scan_params_t.timeout  in the call to sd_ble_gap_connect was set to zero, meaning never timeout.   When setting this to a non-zero value, I do get BLE_GAP_EVT_TIMEOUT(BLE_GAP_TIMEOUT_SRC_CONN).   I had just used the same ble_gap_scan_params_t values from passive scanning, where I really did not want to timeout.
2. I have not seen the GATTC_READ or GATTC_WRITE problem in my test program in 13 days (Feb 27). However, I am seeing it in my product, so I need to investigate the differences between the two.  When I started this support case GATTC_READ was waiting only for event BLE_GATTC_EVT_READ_RSP and GATTC_WRITE was waiting only for event BLE_GATTC_EVT_WRITE_RSP/BLE_GATTC_EVT_WRITE_CMD_TX_COMPLETE. Since then I’ve added checks for events BLE_GAP_EVT_DISCONNECTED and BLE_GATTC_EVT_TIMEOUT.  These changes seemed to almost entirely eliminate this problem from the test program. I have two unexplained facts: a) after making those changes, I did see this problem once, on Feb. 27, with the test program;  b) the logging from debug firmware (attachment 2020-01-24-092119EST-ProductStoppedGettingEventsFromNordicDK.txt) that shows a call to SD_BLE_GATTC_READ with no response event afterwards (BLE_GATTC_EVT_READ_RSP   or BLE_GATTC_EVT_TIMEOUT or BLE_GAP_EVT_DISCONNECTED).  

 

Until I can reproduce this second problem again in a test program, I don’t expect that Nordic can investigate further.   

[Jørgen Holmefjord]

Thanks for the update! Let me know if you are able to reproduce the second issue again and what we need to do to reproduce/investigate it.

[Paul Bradford]

My product intermittently fails to receive an event after a GATTC read/write, but so far my test program does not fail. I'm making the test program incorporate more of the product code, while still being a self-contained test. Still working on it.