Attachments (2) Download All
Nordic Case Info
  • Case ID: 302421
Options

LE Audio timeout behaviour (0x08) interfacing with third party devices.

kieran.cheung

Hi, I'm currently developing a device that acts as an LE Audio client. Everything works as expected when interfacing with an LE Audio server counterpart on a 5340 Audio DK, also using the Zephyr BLE Audio API.

However I recently attempted to interface my client with a third party pair of LE Audio headphones, specifically the Earfun Air Pro 3s, and upon enabling the streams (bt_audio_stream_enable) the device receives no response callback and supposedly hits the supervisory timeout (disconnect reason 0x08.) At first I suspected this may be an issue with the headphones, and I haven't ruled out this possibility.

But then I decided to test the nrF5340 audio application (unmodified) with the Android LE Audio framework in the developer settings, which seems to work decently well with the Earfun Air Pro 3s. I found that the 5340 headset application was successfully receiving and playing back the stream for 4s, but then receives a timeout event and immediately stops playing. 

There's a chance these are unrelated issues but seeing as they both involve supervision timeouts, there's the possibility something is not being handled correctly on the 5340? Can something about the LE Audio framework cause it to stop sending packets to the peer device? Has the audio application been tested with any third party devices?

I have tried changing the clock source with:

CONFIG_CLOCK_CONTROL_NRF_K32SRC_SYNTH=y
As I heard this has been related to other timeout issues, but that doesn't seem to be the cause here as it has no effect.

Log from headset:

HL [00:01:04.268,341] <inf> cis_headset: Connected: 0C:C4:13:2F:AD:44 (public)
HL [00:01:09.610,137] <inf> ble_audio_services: Volume = 10, mute state = 0
HL [00:08:10.497,955] <dbg> bt_audio_stream: bt_audio_stream_attach: conn 0x20002db8 stream 0x2000a728 ep 0x2000ba34 codec 0x2000ba44
HL [00:08:10.587,951] <dbg> bt_audio_stream: bt_audio_stream_iso_listen: stream 0x2000a728 conn 0x20002db8
HL [00:08:10.683,288] <wrn> audio_datapath: I2S RX continuing stream
HL [00:08:10.691,284] <wrn> audio_datapath: I2S RX overrun. Single msg
HL [00:08:10.704,315] <inf> audio_datapath: Drft comp state: INIT
HL [00:08:11.243,072] <dbg> bt_audio_stream: bt_audio_stream_iso_accept: acl 0x20002db8
HL [00:08:11.243,072] <dbg> bt_audio_stream: bt_audio_stream_iso_accept: iso_chan 0x2000bb20
HL [00:08:11.440,124] <inf> audio_datapath: Drft comp state: CALIB
HL [00:08:11.441,101] <wrn> audio_datapath: Data received, total underruns: 755
HL [00:08:11.492,218] <wrn> audio_datapath: Data received, total underruns: 756
HL [00:08:11.540,344] <inf> audio_datapath: Drft comp state: OFFSET
HL [00:08:12.021,820] <inf> audio_datapath: Drft comp state: LOCKED
HL [00:08:12.029,510] <inf> audio_datapath: Pres comp state: MEAS
HL [00:08:12.139,495] <inf> audio_datapath: Pres comp state: WAIT
HL [00:08:12.239,501] <inf> audio_datapath: Pres comp state: INIT
HL [00:08:12.249,511] <inf> audio_datapath: Pres comp state: MEAS
HL [00:08:12.359,497] <inf> audio_datapath: Pres comp state: LOCKED
HL [00:08:16.800,872] <inf> cis_headset: Stream stopped
HL [00:08:16.800,903] <dbg> bt_audio_stream: bt_audio_stream_iso_listen: stream 0x2000a728 conn 0x20002db8
HL [00:08:16.801,727] <inf> cis_headset: Disconnected: 0C:C4:13:2F:AD:44 (public) (reason 0x08)
HL [00:08:16.802,673] <inf> cis_headset: Direct advertising to 0C:C4:13:2F:AD:44 (public) started

Parents
  • 0

    Update: Think upgrading the version of the network controller binary has resolved this issue for the demo application. Will see if it resolves timeout in my original use-case. 

  • 0 in reply to kieran.cheung

    Unfortunately upgrading to the most recent version of the SDK has not resolved the timeout when the 5340 is acting as a gateway/client.

    I have tested the Audio Application on versions 2.2.99-dev3 and 2.2.0 and in both instances a timeout occurs when calling bt_audio_stream_enable() while connected to the Earfun headphones. I have no way of knowing whether this is an issue on the headphones or on the client, however the headphones are able to work with Android on the Google Pixel 7.

    The fact that there was also a (now fixed) timeout related issue in the CIS headset mode in a previous version makes me suspect there may be some issue in the gateway mode within the current version? Has the gateway mode been tested with any third party server devices?

    I made only minor adjustments to attempt to use the application with the headphones, setting presentation delay to 25000 instead of 10000 as the headphones require this, and changing the scanning process to look for the name of the headphones. Plus some logs to show when things are happening.

    Here is the log:

    (bt_audio_stream_enable is called just after QOS is set.)

    GW [00:00:00.259,490] <inf> fw_info: ------- DEBUG BUILD -------
    GW [00:00:00.259,490] <inf> fw_info: Compiled for GATEWAY device
    GW [00:00:00.270,111] <inf> board_version: Compatible board/HW version found: 1.0.0
    GW [00:00:02.305,999] <wrn> bt_hci_core: Controller to host flow control not supported
    GW [00:00:02.309,143] <inf> bt_hci_core: No ID address. App must call settings_load()
    GW [00:00:02.309,204] <inf> ble: MAC: 00:00:00:00:00:00 (public)
    GW [00:00:02.309,783] <inf> ble: Controller version: 3310
    GW [00:00:02.403,839] <inf> cis_gateway: Scanning successfully started
    GW [00:00:07.595,367] <inf> cis_gateway: Found Whitelisted Advertiser
    GW [00:00:07.680,114] <inf> cis_gateway: Connected: 70:5A:6F:60:62:71 (public)
    GW [00:00:11.072,418] <inf> cis_gateway: Scanning successfully started
    GW [00:00:11.851,776] <wrn> bt_unicast_client: No space left to parse ASE
    GW [00:00:12.752,319] <inf> cis_gateway: Stream configured 0x2000b5ac
    GW [00:00:12.752,349] <inf> cis_gateway: LEFT sink stream connected
    GW [00:00:12.812,164] <inf> cis_gateway: QOS Set for stream 0x2000b5ac
    GW [00:00:16.834,625] <inf> cis_gateway: Disconnected: 70:5A:6F:60:62:71 (public) (reason 0x08)

  • 0 in reply to kieran.cheung

    Hello, I received feedback from one in the gruop working with audio, adding it here:

    1. The user tests our headset with Pixel 7 and found the Pixel 7 disconnected after stream start couple seconds later.

    This is a known issue, probably because the Pixel 7 sends a connection parameter request for using 40ms ACL interval, which audio controller is not happy and out of response. From my side I can see that Pixel will try to reconnect the headset again in the latest AOSP Android, and then stream can recover, since Pixel will try to use different connection parameters.

    There might be a quick workaround is that we add connection parameter request callback, return false if interval_min/max is 0x40. But this is something we will check with the audio controller developers.

    It seems during the handshaking, headset will expose the minimal/maximum presentation delay, Pixel chooses the minimal one, but it cannot handle it properly, so glitch happens. We have a PR in the later for telling the Phone uses a higher number.

    2. For the case when nRF5340 gateway connects with Earfun, I would assume Earfun refuse the QoS setting from our gateway. I will check if we can low down the log level to see more details. It is hard to figure out where is the issue (central or peripheral). A sniffer log from Ellisys would provide great help.

    Kenneth

  • 0 in reply to Kenneth

    One question that may help the developers with the debugging: Can you connect to the earbuds with the nRFConnect phone app and see whether there are any LE Audio services there?

    Thanks,
    Kenneth

  • 0 in reply to Kenneth

    Hi Kenneth, 

    Thanks for your response,

    I have noticed the connection interval seems very critical to LE Audio connections with the 5340, but I haven't found any documentation on what exactly is the appropriate value based on the parameters involved. Why does the audio controller not like 40ms for example? 

    I have connected to the headphones via the nRF Connect app and they have Published Audio Capability Service (PACS,) Audio Stream Control Service (ASCS,) Volume Control Service (VCS). I had decoded the PACs on the device (see attached) to check that the parameters I was configuring the stream with were valid.

    Fullscreen Earfun PACs.txt Download

    For QoS the only change I made was to increase the presentation delay to 30000us as the headphones were giving response notifications via the LE Audio service when providing the lower default values. With these changes the configure QoS command appears to give a successful completion callback with no warnings.

    I will look into getting a sniffer log. The way the headphones are behaving during the error looks like it's the headphone that is asserting. It clearly seems to hard-reset before the 5340 detects a timeout. It's just unusual because they work with Android so there must be something different about the connection with the 5340 that it doesn't like.

  • 0 in reply to kieran.cheung

    We are looking into this, can you add the following config in the gateway for getting more information?

    CONFIG_BT_AUDIO_DEBUG_UNICAST_CLIENT=y
    CONFIG_BT_AUDIO_STREAM_LOG_LEVEL_DBG=y
    CONFIG_LOG_BUFFER_SIZE=8192

    Kenneth

  • 0 in reply to Kenneth

    Hi Kenneth,

    Here is the log I get when trying to connect using a build of the 5340 application from version 2.2.99-dev3 with only the following changes in addition to the log flags you mentioned.

    • CONFIG_BT_AUDIO_PRESENTATION_DELAY_US=25000
    • CONFIG_BT_AUDIO_MAX_TRANSPORT_LATENCY_MS=30
    • Connecting to headphones based on their name.

    Fullscreen Connection Attempt Log.txt Download

    After the timeout, at ~15.9s the device then continuously finds and fails to pair to the headphones until I cycle both. I believe this is because the initial headphone that the gateway tries to enable the stream to asserts (it visibly seems to blink red and turn off while the other continues blinking for advertising) and the other one keeps advertising, but security fails because of (I'm guessing) some spec behaviour around pairing to the same address.

    I have also reported this to the headphone manufacturer, but as I noted they work with Android which makes it harder to dismiss the problem as only relevant to the headphone and not the 5340.

    Thanks

Reply
  • 0 in reply to Kenneth

    Hi Kenneth,

    Here is the log I get when trying to connect using a build of the 5340 application from version 2.2.99-dev3 with only the following changes in addition to the log flags you mentioned.

    • CONFIG_BT_AUDIO_PRESENTATION_DELAY_US=25000
    • CONFIG_BT_AUDIO_MAX_TRANSPORT_LATENCY_MS=30
    • Connecting to headphones based on their name.

    Fullscreen Connection Attempt Log.txt Download

    After the timeout, at ~15.9s the device then continuously finds and fails to pair to the headphones until I cycle both. I believe this is because the initial headphone that the gateway tries to enable the stream to asserts (it visibly seems to blink red and turn off while the other continues blinking for advertising) and the other one keeps advertising, but security fails because of (I'm guessing) some spec behaviour around pairing to the same address.

    I have also reported this to the headphone manufacturer, but as I noted they work with Android which makes it harder to dismiss the problem as only relevant to the headphone and not the 5340.

    Thanks

Children
  • 0 in reply to kieran.cheung

    They are discussing this internally, but from the log it seems the headset is OK with the QoS setting, but suddenly headset disconnected. The reason is 0x08, which means headset stop sending any packets. Probably the issue is from headset side. Will let you know if I receive more feedback internally.

    Kenneth

  • +1 in reply to Kenneth

    Hi Kenneth,

    I've just been informed by the headphone manufacturer that their technical team has also encountered this problem when interfacing with certain devices and will be submitting a case with Qualcomm who must be supplying the LE Audio firmware component for the headphones.

    Once I receive an update on this issue I will try again, but for now I'm assuming this bug is completely due to the headphone side.

    Thanks for your help!

Terms of service