nRF52840 with SDK 15.2 running with BLE and Data Length Extension

[SebastianGutzwiller]

Hi all,

I observe a connection supervision timeout (HMI error code 0x08) in my Nordic firmware with certain Android smartphones (controller).

Additional info regarding GATT events: After the last connection parameter update and some GATT events the softdevice stops reporting BLE_GATTS_EVT_HVN_TX_COMPLETE and BLE_GATTS_EVT_WRITE.

After exchanging the MTU request in GATT the controller sends data length update requests over GAP with

• Max number of payload octets to receive of  251 bytes
• Max reception time of 2120 us
• Max number of payload octets to transmit of  135 bytes
• Max transmission time of 1192 us (BAD CASE) and 2120 us (GOOD CASE)

Any ideas?

[SebastianGutzwiller]

/cfs-file/__key/communityserver-discussions-components-files/4/ndk_5F00_s7_5F00_disc_5F00_dur_5F00_login2_5F00_filt.pcapng

Here is a Wireshark trace first of a good case & a bad case.

HTH Sebastian

[SebastianGutzwiller]

1) Open point: We need to check what Bluetooth event can be traced on those Android smartphones.

2) The trace was recorded with a firmware containing S140 v.6.1.1.

[SebastianGutzwiller]

Can I connect to it with a Smartphone app to see if that connection supervision timeout is happening?

[SebastianGutzwiller]

Obviously no.

[Amanda Hsieh]

Hi, 

Sorry for the mistake. I forgot you want to test with the mobile phone.

You could try the Heart Rate Application example.

-Amanda H.

[SebastianGutzwiller]

As my employer is getting impatient I wanted to ask how big are the chances that the error is happening on the Nordic board?

[Amanda Hsieh]

Hi, 

SebastianGutzwiller said:

The reason for disconnect on nRF side has been integrated long time ago, see initial description.

From your nrf-Connect-Log-1.txt, we saw the disconnection reason is Connection terminated by peer (status 19). If you send disconnect request from your peripheral, you get onConnectionStateChanged with status = 19 (0x13 = GATT CONN TERMINATE PEER USER). That is why we want you to print the disconnect reason in the code. However, you indicated the disconnect reason is HMI error code 0x08 and you also said: 

SebastianGutzwiller said:

After several tries with 'nRF Connect' no supervision timeout happened, see one example with BLE_HCI_LOCAL_HOST_TERMINATED_CONNECTION in ndk_s7_nrf_connect.pcapng

You have to identify what is the disconnection reason.  

For BLE_HCI_LOCAL_HOST_TERMINATED_CONNECTION, you have to check if you are calling sd_ble_gap_disconnect(). For BLE_HCI_CONNECTION_TIMEOUT, you will get status = 8 (0x08 = GATT CONN TIMEOUT) on RF connect side if you just restart your device, or you go out of range, or other reason of loss of comms. 

What is the Android OS on your phone? Not sure this post can help or not. 

If you are debugging this with SES, you might find this video useful.

-Amanda H.

[SebastianGutzwiller]

I can guarantee that the nRF52840 does not get a reset nor call sd_ble_gap_disconnect() nor that the smartphone goes out of range.

If you look at 'ndk_s7_disc_dur_login2_filt.pcap' how big are the chances that the error is happening on the Nordic board?

[Amanda Hsieh]

Hi, 

In the ndk_s7_disc_dur_login2_filt.pcap, I see one of the disconnection is terminated by the phone.  Another one, I don't have enough information to know which side caused the disconnection. 

You can compile with the debug mode to print out full the info to debug. 

-Amanda H.

[SebastianGutzwiller]

I updated the SoftDevice to version 7.0.1 and still have the connection supervision timeouts in about 1 of 7 connections with some smartphones.

In those cases I can confirm that the SoftDevice called with sd_ble_gatts_hvx() is always returning NRF_SUCCESS and the SoftDevice stops sending BLE_GATTS_EVT_HVN_TX_COMPLETE filling up the transmit queue on the application side (variant #2 of https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.s140.api.v7.0.1%2Findex.html).

Can the transmission of the Handle Value Notification be prevented by events outside of the SoftDevice? Can one monitor that HVN transmission in more details?

[Amanda Hsieh]

Hi, 

SebastianGutzwiller said:

SoftDevice stops sending BLE_GATTS_EVT_HVN_TX_COMPLETE filling up the transmit queue on the application side

How many NRF_SUCCESS is returned by the sd_ble_gatts_hvx before the softdevice stops sending BLE_GATTS_EVT_HVN_TX_COMPLETE?

How do you know the softdevice stops sending  BLE_GATTS_EVT_HVN_TX_COMPLETE? Could you provide the debug log?

How big is your hvn_tx_queue_size ?

SebastianGutzwiller said:

variant #2 of https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.s140.api.v7.0.1%2Findex.html

I think you mean this GATTS Handle Value Notification. 

SebastianGutzwiller said:

Can one monitor that HVN transmission in more details?

The sd_ble_gatts_hvx can keep track of the available queue element count for notifications by following the procedure below:

• Store initial queue element count in a variable.
• Decrement the variable, which stores the currently available queue element count, by one when a call to this function returns NRF_SUCCESS.
• Increment the variable, which stores the current available queue element count, by the count variable in BLE_GATTS_EVT_HVN_TX_COMPLETE event.

 -Amanda H.

[SebastianGutzwiller]

/cfs-file/__key/communityserver-discussions-components-files/4/nordicapp_5F00_sdk16_5F00_dle_5F00_s7_5F00_connect_5F00_wal_5F00_4.log

That's the trace file logged with one good connection & one failed at the end.