Chrome Version       : 67.0.3396.87 (Official Build) (32-bit)
URLs (if applicable) : https://webbluetoothcg.github.io/demos/bluetooth-printer/
Other browsers tested:
  Add OK or FAIL, along with the version, after other browsers where you
have tested this issue:
     Safari: n/a
    Firefox: n/a (web-bluetooth not supported on firefox for android)
       Edge: n/a

What steps will reproduce the problem?
(1) Purchase Lenovo Tab4 10 tablet model TB-X304F, Android 7.1.1 and ZKC5805 bluetooth printer.
(2) Go to URL above for bluetooth printer demo.
(3) Enter in some text and tap 'PRINT'.

What is the expected result?
After selecting the printer in the pairing dialog box, some output should be printed on the printer.

What happens instead?
The page allows me to select the printer from the pairing dialog box. The printer appears as ZKCBTMV1, but no printout occurs, just this Error: Could not connect to bluetooth device!

Please provide any additional information below. Attach a screenshot if
possible.

The printer is a ZKC 5805 that supports bluetooth 4.  I can print from chrome from my Samsung S8 Phone, but the tablet doesn't connect.

I have attached output from adb logcat for the tablet, filtered with:

adb logcat -d -v time | grep -E "[Bb]luetooth|cr.Bluetooth|BtGatt|BluetoothGatt|bt_bt"

I have also attached logcat output from our web application, which also works ok with the phone.

My app uses the same service and characteristic as the bluetooth demo and works ok with the phone, but not with the Tablet.  The ZKC printer only seems to support sending up to 20 bytes of data at a time, whereas the demo sends 512 bytes, but the problem seems to be connecting from the tablet, not the data transmission.

In the nRF android app, the printer bonds ok, but doesn't connect either, please see screenshot.  nRF connects ok from the Samsung phone however. So this may be a lenovo, android or printer problem.
 

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tablet-logs.zip 2.8 KB Download

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	Screenshot_2018-07-30-18-17-15-447.jpeg 221 KB View Download