Scan with transport=auto delivers unreliable scan results.

[dezi]

Hi,

i had trouble connecting a ble thermometer to my app under ubuntu/linux.

The device did not reliable show up in the discovery.

Changing the scan parameters from transport=auto to transport=le fixed the problem.

Problem now: I also have to discover br/edr devices at the same time.

Workaround solution:

Switching the DiscoveryFilter-Set from transport=le to transport=bredr
every 250 ms while the discovery is still active.

Interestingly, this workaround also fixes my problem from issue

#572

Regards, dezi

Excerpt from btmon log:

@ MGMT Command: Start Service Di.. (0x003a) plen 4 {0x0001} [hci0] 2463.114751
Address type: 0x06
LE Public
LE Random
RSSI: invalid (0x7f)

@ MGMT Command: Stop Discovery (0x0024) plen 1 {0x0001} [hci0] 2463.511880
Address type: 0x06
LE Public
LE Random
< HCI Command: LE Set Extend.. (0x08|0x0042) plen 6 #134809 [hci0] 2463.511920

@ MGMT Command: Start Service Di.. (0x003a) plen 4 {0x0001} [hci0] 2463.516787
Address type: 0x01
BR/EDR
RSSI: invalid (0x7f)
UUIDs: 0

@ MGMT Command: Stop Discovery (0x0024) plen 1 {0x0001} [hci0] 2463.613490
Address type: 0x01
BR/EDR
< HCI Command: Inquiry Cancel (0x01|0x0002) plen 0 #134813 [hci0] 2463.613537

HCI Event: Command Complete (0x0e) plen 4 #134814 [hci0] 2463.618589

[jsmif]

@dezi how specifically did you do this workaround?

Workaround solution:

Switching the DiscoveryFilter-Set from transport=le to transport=bredr
every 250 ms while the discovery is still active.

Based on my observations which I posted in #572 I suspect the workaround is working because although bluetoothctl dies, you're effectively restarting it every 250ms. So I am interested in using that workaround for now too until #572 is fixed, if it's something easily scriptable from the CLI.

[dezi]

@jsmif

I have a self developed long term go process running, which uses the go-package github.com/muka/go-bluetooth.

The package is based on the bluez dBus interfaces and has api methods to start/stop scanning.

[Vudentz]

Looks like a duplicated of #510, try with the following change: bluez/bluetooth-next@52bf4fd