11 Replies Latest reply on Dec 11, 2018 7:01 AM by Leonid Kaleda

Android can't reliably connect to Zebra via BLE when BT classic is enabled

Michael Heins Aug 3, 2018 8:06 AM

We have an iOS app that we are re-doing for Android. We typically connect with ZD4xx family printers via wifi, BLE or BT classic, depending on customer requirements. Typically all 3 of those interfaces are active. On iOS we are able to reliably discover and connect to the printers via BLE, but on Android, the connect attempt usually fails. If we disable the BT classic interface on the printer, the BLE connections usually succeed (but that is not a viable solution for us). The behavior is the same with different Android platforms and Android OS versions that we have tried.

Our speculation is that the reason may be that the printer is advertising the BLE and BT classic with the same MAC address on both interfaces, and that this confuses the Android Bluetooth stack. We speculate that if BLE and BT classic were advertising with different MAC addresses, the problem would go away.

Our questions are: Has anyone else has observed this problem? Has anyone found a solution? Is there any way to programmatically set a different MAC address for the two Bluetooth interfaces?

Thank you.

Michael Heins

Re: Android can't reliably connect to Zebra via BLE when BT classic is enabled

Steven Si Aug 3, 2018 11:02 AM (in response to Michael Heins)

Hi Michael,

Do you have a test app to share that we can reproduce this problem? We would like to see if this happens during the discovery or happens after connected.
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- Re: Android can't reliably connect to Zebra via BLE when BT classic is enabled
  
  Michael Heins Aug 6, 2018 8:13 AM (in response to Steven Si)
  
  Our Android guy used an Android app called "nRF Connect" to test it independently of our BLE app code.
  
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  - Re: Android can't reliably connect to Zebra via BLE when BT classic is enabled
    
    Steven Si Aug 6, 2018 2:06 PM (in response to Michael Heins)
    
    ...but on Android, the connect attempt usually fails. ...
    What specific device and Android version do you use when you observed this problem? I've tried nRF Connect on Zebra TC56 and was able to connect to the ZD410 over BLE straight away.
    
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    - Re: Android can't reliably connect to Zebra via BLE when BT classic is enabled
      
      Adam Burnett Aug 6, 2018 2:38 PM (in response to Steven Si)
      
      Hi Steven,
      
      I'm the Android guy referred to previously. I have tested this on the following platforms:
      Kindle Fire 7 (Android 5.1.1).
      Google Pixel XL (Android 8.1).
      Lenovo TB-X103F (Android 6.0).
      
      I initially discovered this when placing our Zebra ZD410 into "Smart Only" mode in the connection parameters and turning off the WiFi. The Zebra Printer Setup app (Android) fails to discover or connect when the connection is forced over BLE (i.e. smart mode).
      
      On a separate note, from nRF Connect I can connect to a printer on all of the platforms listed above fairly regularly when I put the printer into "Smart Only" mode. It seems the problem occurs when both BLE and Classic are enabled for a printer.
      
      Thanks for your help Steven,
      Adam Burnett
      
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Re: Android can't reliably connect to Zebra via BLE when BT classic is enabled

Leonid Kaleda Nov 28, 2018 11:12 PM (in response to Michael Heins)
I am experiencing the same problem with ZQ520. I have tested it across multiple Android devices and if the printer is put into "Low Energy Only" mode all of them are able to connect without any problems. Interestingly, one of my devices (Galaxy S7) is able to connect to the printer in "Classic & Low Energy" mode. According to the system logs the problem is not that Android is not able to open GATT connection to the printer but that BLE service discovery procedure never finishes or returns GATT error 129. Unfortunately "Classic & Low Energy" is a default mode and we have to ask all users of our app to configure their printers before first use. Here is the list of devices I tried:

Nexus 5X (8.1.0)
Samsung Galaxy J1 (4.4)
Samsung Galaxy J3 (5.1.1)
Samsung Galaxy S7 (6.0)
Samsung Galaxy Tab S3 (7.0)
Xiaomi Redmi 4 (6.0.1)

My printer's serial number is XXRBJ182902108. Is there any information I could provide you to troubleshoot the issue?
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- Re: Android can't reliably connect to Zebra via BLE when BT classic is enabled
  
  Steven Si Nov 29, 2018 6:58 AM (in response to Leonid Kaleda)
  
  Hi Leonid,
  
  Are you experiencing this problem with your own app or with Zebra Setup Utilities app for Android? If it's your app, would you share the app or the trimmed-down version of your app, so that we can reproduce the problem?
  
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  - Re: Android can't reliably connect to Zebra via BLE when BT classic is enabled
    
    Leonid Kaleda Dec 2, 2018 10:57 PM (in response to Steven Si)
    
    Hi Steven,
    From what I can gather Zebra Setup Utility app for Android uses classic bluetooth to connect to the printer. If I disable classic bluetooth using Zebra Setup Utility app for Desktop mobile version is not able to connect to the printer. Moreover, you do not need to use my app to reproduce the issue, even BLE Scanner app BLE Scanner - Apps on Google Play , which is pretty popular bluetooth app for Android, fails to discover services when the printer is in "Classic & Low Energy" mode. Interestingly, but we did not have the problem until we had iOS version of our app connected to the printer. It might be some implicit bonding issue but I have already tried to reset all possible communication settings using Zebra Setup Utility for Desktop.
    
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    - Re: Android can't reliably connect to Zebra via BLE when BT classic is enabled
      
      Robin West Dec 3, 2018 12:52 PM (in response to Leonid Kaleda)
      
      Hi Leonid,
      Have you updated your firmware on the printer? This was issue was corrected a year or two ago in the printer firmware. Printers | Support & Downloads | Zebra
      
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      - Re: Android can't reliably connect to Zebra via BLE when BT classic is enabled
        
        Leonid Kaleda Dec 11, 2018 6:56 AM (in response to Robin West)
        
        Sorry for the delay. I have updated my firmware. Now it is V76.20.15Z, but problem persists.
        
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    - Re: Android can't reliably connect to Zebra via BLE when BT classic is enabled
      
      Steven Si Dec 4, 2018 2:45 PM (in response to Leonid Kaleda)
      
      From what I can gather Zebra Setup Utility app for Android uses classic bluetooth to connect to the printer.
      Just want to clarify that the above statement is not accurate. The Zebra Printer Setup Utilities work with both Bluetooth Classic and Low Energy on the printers. When both Classic and LE are enabled on the printer, the Setup Utilities will use Classic to connect to the printer. When only LE is enabled on the printer, the Setup Utilities will use LE to connect to the printer. We can differentiate whether the Setup Utilities uses Classic or LE by looking at the Bluetooth icon on each entry in the list of discovered printers. If the Bluetooth icon has a "4.0" next to it, this means that the Setup Utilities is using LE to connect to the printer. If there is no "4.0" next to the Bluetooth icon, it means the Setup Utilities uses Classic to connect to the printer.
      
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      - Re: Android can't reliably connect to Zebra via BLE when BT classic is enabled
        
        Leonid Kaleda Dec 11, 2018 7:01 AM (in response to Steven Si)
        
        Sorry for the delay. Thank you for the explanation. If I put my printer into "Low Energy Only" mode Zebra Printer Setup Utility - Apps on Google Play fails to connect to the printer. "Classic & Low Energy" and "Classic Only" modes work just fine.
        
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