hcitool scan times
Hi,
I want to monitor what BT devices come into range of mt BT stick for automation. For this I'm currently just using 'hcitool scan' in a loop. Sometimes the scan is pretty quick, 2-3 seconds, but most of the time the scan takes about 13 seconds, which is too long for my purposes. Can I influence these scan times somehow, possibly even with a setting on the palm/phone itself? Why do the scan times vary so much?
Thanks,
Emiliano
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hello emiliano
read the bluetooth specification.
you've to allow remote devices ~10.5 seconds to answer... so 13 seconds makes sense...
that it is so fast from time to time is, because a cached result is returned. look at the source of hcitool for more information...
regards
Marco
Quoted 14 lines · Emiliano Heyns
Hi,
I want to monitor what BT devices come into range of mt BT stick for automation. For this I'm currently just using 'hcitool scan' in a loop. Sometimes the scan is pretty quick, 2-3 seconds, but most of the time the scan takes about 13 seconds, which is too long for my purposes. Can I influence these scan times somehow, possibly even with a setting on the palm/phone itself? Why do the scan times vary so much?
Thanks,
Emiliano
Quoted 11 lines
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Quoted 7 lines · Marco Trudel
hello emiliano
read the bluetooth specification.
you've to allow remote devices ~10.5 seconds to answer... so 13 seconds makes sense...
that it is so fast from time to time is, because a cached result is returned. look at the source of hcitool for more information...
OK, thanks. This could actually work to my benefit if I disable the hcitool cache -- the device could take the time the user takes from walking into range to being at the device for detecting, if you walk out of range before that you were only passing the device. Good. Now I only have to look at average office walking speeds to see how great I want this radius to be :)
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Quoted 11 lines · Emiliano Heyns
Quoted 7 lines · Marco Trudel
hello emiliano
read the bluetooth specification.
you've to allow remote devices ~10.5 seconds to answer... so 13 seconds makes sense...
that it is so fast from time to time is, because a cached result is returned. look at the source of hcitool for more information...
Quoted 2 lines
OK, thanks. This could actually work to my benefit if I disable the hcitool cache --
you're welcome...
Quoted 2 lines
the device could take the time the user takes from walking into range to being at the device for detecting,
I don't know what you mean with this...
Quoted 4 lines
if you walk
out of range before that you were only passing the device. Good. Now I only have to look at average office walking speeds to see how great I want this radius to be :)
I don't understand that as well, but it sounds very interesting. Can you explain what you're doing? Just curious...
by the way: do you know that a device does not have to answer to an inquiry? if a device is busy or just decides to not answer to an inquiry, that's ok (defined in bluetooth specification, my experience showed this as well)...
regards
Marco
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Quoted 10 lines · Marco Trudel
Quoted 2 lines
OK, thanks. This could actually work to my benefit if I disable the hcitool cache --
you're welcome...
Quoted 2 lines
the device could take the time the user takes from walking into range to being at the device for detecting,
I don't know what you mean with this...
Quoted 7 lines
Quoted 4 lines
if you walk
out of range before that you were only passing the device. Good. Now I only have to look at average office walking speeds to see how great I want this radius to be :)I don't understand that as well, but it sounds very interesting. Can you explain what you're doing? Just curious...
We have a kiosk where you have to select your name from a list before you can do anything useful. You pick your name from a scrollist. What I want to try is to install a bluetooth adapter on the device, allow people to register their BT toys (phone, palm, whatever), and have the device scan for BT devices in the vicinity. If it recognizes a registered device, it could pre-select your name from the list, for convenience.
If BT scan was super-fast, anyone standing at the device would be bothered by anyone else passing by with a BT gadget active. With a 13 sec discovery time, and given the right range, passers-by would be out of range before actually being picked up. And if the range is just wide enough, the scan would start at the edge of that range, and would finish some seconds after you're standing at the device. It'd take some tweaking, but since people usually slow their pace before stopping, it could work.
Quoted 4 lines
by the way: do you know that a device does not have to answer to an inquiry? if a device is busy or just decides to not answer to an inquiry, that's ok (defined in bluetooth specification, my experience showed this as well)...
If we'll be using this (it's just a friday afternoon experiment at this point) it's just an add-on for convenience. There will actually only be a minority of our users that will be carrying active BT gadgets.
Emiliano
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Marcel Holtmann
maintainerHi Emiliano,
Quoted 7 lines
I want to monitor what BT devices come into range of mt BT stick for automation. For this I'm currently just using 'hcitool scan' in a loop. Sometimes the scan is pretty quick, 2-3 seconds, but most of the time the scan takes about 13 seconds, which is too long for my purposes. Can I influence these scan times somehow, possibly even with a setting on the palm/phone itself? Why do the scan times vary so much?
look at the periodic inquiry stuff of the HCI.
Regards
Marcel
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