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NordicSemiconductor / Android-BLE-Library

A library that makes working with Bluetooth LE on Android a pleasure. Seriously.
BSD 3-Clause "New" or "Revised" License
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Connection interval changes on its own #558

Open arthurianno opened 3 months ago

arthurianno commented 3 months ago

Hello,

I'm writing an android application, using no.nordicsemi.android:ble:2.3.1. I connect to the sensor and write 49KB data to it. Before recording, I set the desired interval (CONNECTION_PRIORITY_HIGH 11.25 - 15ms) and MTU (247). Next, I initiate the sending of files of 128, 232,240 bytes. But the problem is that after sending, GATT sets me to interval 36 and not 12ms as I need. The sensor supports from 12 to 30ms. I tried different versions of Android and the BLE version doesn't really make a difference either. If you need the code, I can show you some excerpts.

Nothing helps, maybe there are some articles or something similar.

UPD uploaded HCI log

https://dropmefiles.com/SEgPo two files

Before sending all data, I put this:

requestConnectionPriority(ConnectionPriorityRequest.CONNECTION_PRIORITY_HIGH) 
    .done(device -> Log.e("BleControlManager", "Interval request sent")) 
    .fail((device, status) -> Log.e("BleControlManager", "Failed to send Interval request: " + status)) 
    .enqueue(); 
requestMtu(247) 
    .done(device -> Log.e("BleControlManager", "MTU request sent ")) 
    .fail((device, status) -> Log.e("BleControlManager", "Failed to send MTU request: " + status)) 
    .enqueue();

Then I receive a log from Gatt:

2024-04-17 15:03:59.776 18358-18412 BluetoothGatt com.example.bluetoothcontrol D onConfigureMTU() - Device=38:3B:26:7E:76:9B mtu=247 status=0
2024-04-17 15:03:59.910 18358-18412 BluetoothGatt com.example.bluetoothcontrol D onConnectionUpdated() - Device=38:3B:26:7E:76:9B interval=12 latency=0 timeout=500 status=0

Then several packets pass through to the device, and then this happens:

2024-04-17 15:04:00.405 18358-18412 BluetoothGatt com.example.bluetoothcontrol D onConnectionUpdated() - Device=38:3B:26:7E:76:9B interval=36 latency=0 timeout=100 status=0

The log shows, that after sending the packet, the interval changes without my participation:

1704 330.000533 SamsungElect_3a:0a:01 (Galaxy A7 (2018)) JiangsuQinhe_7e:76:9b (SatelliteOnline0000) ATT 12 Sent Exchange MTU Request, Client Rx MTU: 247 
1703 329.798134 controller host HCI_EVT 7 Rcvd Command Status (LE Connection Update) 
1705 330.014861 controller host HCI_EVT 8 Rcvd Number of Completed Packets 
1706 330.059797 JiangsuQinhe_7e:76:9b (SatelliteOnline0000) SamsungElect_3a:0a:01 (Galaxy A7 (2018)) ATT 12 Rcvd Exchange MTU Response, Server Rx MTU: 255 
1707 330.060311 host controller HCI_CMD 10 Sent LE Set Data Length 
1708 330.064660 controller host HCI_EVT 9 Rcvd Command Complete (LE Set Data Length) 
1762 330.616503 controller host HCI_EVT 8 Rcvd Number of Completed Packets 
1763 330.616628 SamsungElect_3a:0a:01 (Galaxy A7 (2018)) JiangsuQinhe_7e:76:9b (SatelliteOnline0000) L2CAP 15 Sent Connection Parameter Update Response (Accepted) 
1764 330.617120 host controller HCI_CMD 18 Sent LE Connection Update 
1765 330.617907 controller host HCI_EVT 7 Rcvd Command Status (LE Connection Update) 
1766 330.630105 JiangsuQinhe_7e:76:9b (SatelliteOnline0000) SamsungElect_3a:0a:01 (Galaxy A7 (2018)) ATT 10 Rcvd Write Response, Handle: 0x0013 (Nordic UART Service: Nordic UART Rx: Client Characteristic Configuration)
philips77 commented 3 months ago

Hello,

[!Note] I fixed your post, making it more readable. Please, make sure it's readable next time.

The minimum Interval Connection supported by Android is 11.25 ms, depending on Android version. Here you can find the current values for each "priority": https://cs.android.com/android/platform/superproject/main/+/main:packages/modules/Bluetooth/android/app/res/values/config.xml;l=27;drc=3d19fbcc09b1b44928639b06cd0b88f735cd988d;bpv=1;bpt=0

However, Android requests interval 7.5 ms for service discovery, and switches back to higher one afterwards. It may also change to any value it wants without user interaction. I guess this is what you observe. Often phones reserve some percentage of radio for "companion devices", to improve user experience. Or they just want to lower battery consumption.

If you want to send large amount of data, you don't really want short connection interval. Remember, that when using Write Without Response, or Notifications, the phone may send multiple packets in a single connection interval. By using Date Length Extension (DLE), supported on Android 6+, as far as I remember, the Link Layer packets can send fill 247 bytes in a single packet, but can send multiple such packets one by one, which is faster than sending one per connection interval. So, with too short interval it may be that 2 won't fit. Depending on the length of the "unused" gap between end of the last packet and start of the new interval the upload may be faster or slower. Sometimes increasing the interval increases speed.

If you have a good BLE sniffer, like Ellisys, which can show the packets on a time graph, you may tune the connection interval so that as litle time is "wasted" as possible.

If your phone sets the interval to 30 ms, I wound't fight with it, rather would tune the MTU so that the packets fit as much as possible. Also, if your device supports even higher MTU, I recommend using value 498. With that a single GATT packet fits into 2 maximum-length Link Layer packets when using DLE.

arthurianno commented 3 months ago

Hello!

Thank you for correcting the post, I would like to clarify that at the moment the interval of 30ms has been corrected to 12 and now the HCI logs look like this, can you be more specific about what the reason could be??

First of all, I connect, set the MTU and then start working with files

39598   426639.081070   JiangsuQinhe_7e:76:9b (SatelliteOnline0008) localhost (Galaxy A7 (2018))    ATT 19  Rcvd Handle Value Notification, Handle: 0x0012 (Nordic UART Service: Nordic UART Rx)
39599   426639.081521   controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
39600   426639.088081   localhost (Galaxy A7 (2018))    JiangsuQinhe_7e:76:9b (SatelliteOnline0008) ATT 12  Sent Exchange MTU Request, Client Rx MTU: 247
39601   426639.125563   controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
39602   426639.188328   controller  host    HCI_EVT 19  Rcvd LE Meta (LE Advertising Report)
39603   426639.188790   controller  host    HCI_EVT 46  Rcvd LE Meta (LE Advertising Report)
39604   426639.215277   JiangsuQinhe_7e:76:9b (SatelliteOnline0008) localhost (Galaxy A7 (2018))    ATT 12  Rcvd Exchange MTU Response, Server Rx MTU: 252
39605   426639.215661   host    controller  HCI_CMD 10  Sent LE Set Data Length
39606   426639.216416   controller  host    HCI_EVT 9   Rcvd Command Complete (LE Set Data Length)
39607   426639.220878   localhost (Galaxy A7 (2018))    JiangsuQinhe_7e:76:9b (SatelliteOnline0008) ATT 255 Sent Write Request, Handle: 0x0010 (Nordic UART Service: Nordic UART Tx)
39608   426639.350541   controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
39609   426639.395584   JiangsuQinhe_7e:76:9b (SatelliteOnline0008) localhost (Galaxy A7 (2018))    ATT 10  Rcvd Write Response, Handle: 0x0013 (Nordic UART Service: Nordic UART Rx: Client Characteristic Configuration)
39610   426639.399510   localhost (Galaxy A7 (2018))    JiangsuQinhe_7e:76:9b (SatelliteOnline0008) ATT 255 Sent Write Request, Handle: 0x0010 (Nordic UART Service: Nordic UART Tx)
39611   426639.438742   controller  host    HCI_EVT 13  Rcvd LE Meta (LE Connection Update Complete)
39612   426639.439502   controller  host    HCI_EVT 7   Rcvd Command Status (No Operation)
39511   426636.712040   controller  host    HCI_EVT 7   Rcvd Command Status (LE Read Remote Features)
39512   426636.741018   controller  host    HCI_EVT 15  Rcvd LE Meta (LE Read Remote Features Complete)
39513   426636.741593   host    controller  HCI_CMD 6   Sent Read Remote Version Information
39514   426636.743243   controller  host    HCI_EVT 7   Rcvd Command Status (Read Remote Version Information)
39515   426636.875833   controller  host    HCI_EVT 11  Rcvd Read Remote Version Information Complete
39516   426636.881483   host    controller  HCI_CMD 18  Sent LE Connection Update
39517   426636.882437   localhost (Galaxy A7 (2018))    JiangsuQinhe_7e:76:9b (SatelliteOnline0008) ATT 16  Sent Read By Group Type Request, Primary Service, Handles: 0x0001..0xffff
39518   426636.883072   controller  host    HCI_EVT 7   Rcvd Command Status (LE Connection Update)
39519   426636.884345   controller  host    HCI_EVT 19  Rcvd LE Meta (LE Advertising Report)
39520   426636.885467   controller  host    HCI_EVT 46  Rcvd LE Meta (LE Advertising Report)
39521   426636.920974   controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
39522   426636.965860   controller  host    HCI_EVT 13  Rcvd LE Meta (LE Connection Update Complete)
39523   426637.010471   JiangsuQinhe_7e:76:9b (SatelliteOnline0008) localhost (Galaxy A7 (2018))    ATT 23  Rcvd Read By Group Type Response, Attribute List Length: 2, Generic Access, Generic Attribute

Further, during the file transfer process, the interval changes again to 12ms.

39654   426639.787868   JiangsuQinhe_7e:76:9b (SatelliteOnline0008) localhost (Galaxy A7 (2018))    ATT 19  Rcvd Handle Value Notification, Handle: 0x0012 (Nordic UART Service: Nordic UART Rx)
39655   426639.788557   controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
39656   426639.800704   JiangsuQinhe_7e:76:9b (SatelliteOnline0008) localhost (Galaxy A7 (2018))    ATT 10  Rcvd Write Response, Handle: 0x0013 (Nordic UART Service: Nordic UART Rx: Client Characteristic Configuration)
39657   426639.807843   localhost (Galaxy A7 (2018))    JiangsuQinhe_7e:76:9b (SatelliteOnline0008) ATT 255 Sent Write Request, Handle: 0x0010 (Nordic UART Service: Nordic UART Tx)
39658   426639.817814   JiangsuQinhe_7e:76:9b (SatelliteOnline0008) localhost (Galaxy A7 (2018))    ATT 19  Rcvd Handle Value Notification, Handle: 0x0012 (Nordic UART Service: Nordic UART Rx)
39659   426639.819035   controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
39660   426639.830895   JiangsuQinhe_7e:76:9b (SatelliteOnline0008) localhost (Galaxy A7 (2018))    ATT 10  Rcvd Write Response, Handle: 0x0013 (Nordic UART Service: Nordic UART Rx: Client Characteristic Configuration)
39661   426639.841405   localhost (Galaxy A7 (2018))    JiangsuQinhe_7e:76:9b (SatelliteOnline0008) ATT 255 Sent Write Request, Handle: 0x0010 (Nordic UART Service: Nordic UART Tx)
39662   426639.847761   JiangsuQinhe_7e:76:9b (SatelliteOnline0008) localhost (Galaxy A7 (2018))    ATT 19  Rcvd Handle Value Notification, Handle: 0x0012 (Nordic UART Service: Nordic UART Rx)
39663   426639.848611   controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
39664   426639.860603   JiangsuQinhe_7e:76:9b (SatelliteOnline0008) localhost (Galaxy A7 (2018))    L2CAP   21  Rcvd Connection Parameter Update Request
39665   426639.861550   localhost (Galaxy A7 (2018))    JiangsuQinhe_7e:76:9b (SatelliteOnline0008) L2CAP   15  Sent Connection Parameter Update Response (Accepted)
39666   426639.862666   host    controller  HCI_CMD 18  Sent LE Connection Update
39667   426639.864004   controller  host    HCI_EVT 7   Rcvd Command Status (LE Connection Update)
39668   426639.864655   controller  host    HCI_EVT 13  Rcvd LE Meta (LE Connection Update Complete)
39669   426639.876053   JiangsuQinhe_7e:76:9b (SatelliteOnline0008) localhost (Galaxy A7 (2018))    ATT 10  Rcvd Write Response, Handle: 0x0013 (Nordic UART Service: Nordic UART Rx: Client Characteristic Configuration)
39670   426639.876970   controller  host    HCI_EVT 8   Rcvd Number of Completed Packets

The logs show that I’m transferring files to the device and for some reason it’s set to 12ms again, although previously it was 30, but now it’s fixed. This is an excerpt of the logs, I will attach the full logs

arthurianno commented 3 months ago

btsnoop_hci.log