Different respones to BLE scan from a Peripheral device?

Different respones to BLE scan from a Peripheral device?

[John Whitmore]

Hello all,

I'm running on two identical embedded Linux Gateway devices, both on
Ubuntu 16.04 and Bluez 5.37. That's certainly an older version, but
it's part and parcel of that version of Ubuntu. I'm having an issue
where the two identical gateway devices are getting different
responses from a BLE scan, and can't figure out what would be the
cause. In both cases it's the same peripheral device, a TI CC2650
device. On one gateway I get a truncated response with just the MAC
address and in the other I get the MAC address plus the description
string "CC2650.."

[bluepy.btle:37] Got: 'rsp=$scan\x1eaddr=b546C0E530068\x1etype=h1\x1erssi=h43\x1eflag=h0\x1ed=b020105030280AA06FF0D0003000011094343323635302053656E736F72546167051208002003020A00\n'

[bluepy.btle:37] Got: 'rsp=$scan\x1eaddr=b546C0E530068\x1etype=h1\x1erssi=h28\x1eflag=h0\x1ed=b020105030280AA06FF0D00030000\n'

I'm probably going to have to get a Bluetooth sniffer device to trace
this issue, but if anybody had any idea what this would be the case,
I'd love to hear.

Perhaps even though the Gateways are running the same Hardware and
Software there might be a Hardware difference in the chipset used or
something. It's all I can think of. Hopefully get something to help
diagnose this issue.

In those two messages there is a difference in RSS, is that signal
strength and could that be the issue? Have to open things up.

Thanks in advance for any help, and apologies I'm at the wrong end of
a learning curve.

John

Re: Different respones to BLE scan from a Peripheral device?

[Emil Lenngren]

Hi John,

Den fre 31 maj 2019 kl 14:27 skrev John Whitmore <arigead@gmail.com>:
>
> Hello all,
>
> I'm running on two identical embedded Linux Gateway devices, both on
> Ubuntu 16.04 and Bluez 5.37. That's certainly an older version, but
> it's part and parcel of that version of Ubuntu. I'm having an issue
> where the two identical gateway devices are getting different
> responses from a BLE scan, and can't figure out what would be the
> cause. In both cases it's the same peripheral device, a TI CC2650
> device. On one gateway I get a truncated response with just the MAC
> address and in the other I get the MAC address plus the description
> string "CC2650.."
>
> [bluepy.btle:37] Got: 'rsp=$scan\x1eaddr=b546C0E530068\x1etype=h1\x1erssi=h43\x1eflag=h0\x1ed=b020105030280AA06FF0D0003000011094343323635302053656E736F72546167051208002003020A00\n'
>
> [bluepy.btle:37] Got: 'rsp=$scan\x1eaddr=b546C0E530068\x1etype=h1\x1erssi=h28\x1eflag=h0\x1ed=b020105030280AA06FF0D00030000\n'
>
> I'm probably going to have to get a Bluetooth sniffer device to trace
> this issue, but if anybody had any idea what this would be the case,
> I'd love to hear.
>
> Perhaps even though the Gateways are running the same Hardware and
> Software there might be a Hardware difference in the chipset used or
> something. It's all I can think of. Hopefully get something to help
> diagnose this issue.
>
> In those two messages there is a difference in RSS, is that signal
> strength and could that be the issue? Have to open things up.
>
> Thanks in advance for any help, and apologies I'm at the wrong end of
> a learning curve.
>
> John

You could try running btmon in a terminal to show the HCI traffic.
There you should see the raw advertising packets in form of LE
Advertising Report packets. You should see both ADV_IND packets as
well as SCAN_RSP packets. Maybe the software doesn't always combine
them and that's why you get different results. And yes RSSI is signal
strength.

/Emi

Re: Different respones to BLE scan from a Peripheral device?

[John Whitmore]

On Fri, May 31, 2019 at 04:30:38PM +0200, Emil Lenngren wrote:
> Hi John,
> 
> Den fre 31 maj 2019 kl 14:27 skrev John Whitmore <arigead@gmail.com>:
> >
> > Hello all,
> >
> > I'm running on two identical embedded Linux Gateway devices, both on
> > Ubuntu 16.04 and Bluez 5.37. That's certainly an older version, but
> > it's part and parcel of that version of Ubuntu. I'm having an issue
> > where the two identical gateway devices are getting different
> > responses from a BLE scan, and can't figure out what would be the
> > cause. In both cases it's the same peripheral device, a TI CC2650
> > device. On one gateway I get a truncated response with just the MAC
> > address and in the other I get the MAC address plus the description
> > string "CC2650.."
> >
> > [bluepy.btle:37] Got: 'rsp=$scan\x1eaddr=b546C0E530068\x1etype=h1\x1erssi=h43\x1eflag=h0\x1ed=b020105030280AA06FF0D0003000011094343323635302053656E736F72546167051208002003020A00\n'
> >
> > [bluepy.btle:37] Got: 'rsp=$scan\x1eaddr=b546C0E530068\x1etype=h1\x1erssi=h28\x1eflag=h0\x1ed=b020105030280AA06FF0D00030000\n'
> >
> > I'm probably going to have to get a Bluetooth sniffer device to trace
> > this issue, but if anybody had any idea what this would be the case,
> > I'd love to hear.
> >
> > Perhaps even though the Gateways are running the same Hardware and
> > Software there might be a Hardware difference in the chipset used or
> > something. It's all I can think of. Hopefully get something to help
> > diagnose this issue.
> >
> > In those two messages there is a difference in RSS, is that signal
> > strength and could that be the issue? Have to open things up.
> >
> > Thanks in advance for any help, and apologies I'm at the wrong end of
> > a learning curve.
> >
> > John
> 
> You could try running btmon in a terminal to show the HCI traffic.
> There you should see the raw advertising packets in form of LE
> Advertising Report packets. You should see both ADV_IND packets as
> well as SCAN_RSP packets. Maybe the software doesn't always combine
> them and that's why you get different results. And yes RSSI is signal
> strength.
> 
> /Emi

Thank you for that. I'll have a look into that and see if I can't get to the
bottom of this issue.