Really? Tires are Bluetooth? I don't think mine are, but now I want to figure out how that works. 1600Chips/sec is 600 microseconds per chip. They spin at up to, say, radial rates that are a 100 revs/sec and thus take maybe 10 msec. to travel 30 cm. How much warble in a chip frequency is there?
Ok, maybe they only need to work when the car is stopped.
I would design a tire pressure system that sends, maybe, 10 bits per second, at most. Or calibrate the sensor to produce 1 bit, and use the car metal frame to carry the signal to the computer as a single bit. A very slowly varying sensor can be sensed without needing a battery, by using some passive, tuned circuit.
Bluetooth is way overkill, but cheap. I doubt it works well in the application, though.
-----Original
From: "David Lang" <[email protected]>
Sent: Mon, Nov 19, 2018 at 9:12 pm
To: "Dave Taht" <[email protected]>
Cc: "Dave Taht" <[email protected]>, "Rajkumar Manoharan" <[email protected]>, "Make-Wifi-fast" <[email protected]>, "linux-wireless" <[email protected]>, "ath10k" <[email protected]>, "Ben Greear" <[email protected]>, "Felix Fietkau" <[email protected]>
Subject: Re: [Make-wifi-fast] [PATCH v3 3/6] mac80211: Add airtimeaccounting and scheduling to TXQs
On Mon, 19 Nov 2018, Dave Taht wrote:
>> I'm not sure if this was a fluke or not, but at Starbucks recently I sat outside,
>> right next to their window, and could not scan their AP at all. Previously, I sat
>> inside, 3 feet away through the glass, and got great signal. I wonder what that was
>> all about! Maybe special tinting that blocks RF? Or just dumb luck of some sort.
>
> Ya know, I could definitely see a market for a material like that! I'd
> like it for my car, so bluetooth wouldn't escape.
That would break your tire pressure sensors (each car is rolling around
broadcasting 4 unique bluetooth IDs, not hard to track)
David Lang
_______________________________________________
Make-wifi-fast mailing list
[email protected]
https://lists.bufferbloat.net/listinfo/make-wifi-fast
This is getting seriously offtrack for such a wide set of mailing
lists. Tis OK were it just make-wifi-fast, and
I'd encourage limiting the distribution in the future to just that.
that said, I'm tired of looking at patches this week, and this song's
going through my head. so... join in, and...
https://www.youtube.com/watch?v=W5_8U4j51lI
On Wed, Nov 21, 2018 at 7:28 AM David P. Reed <[email protected]> wrote:
>
> Really? Tires are Bluetooth? I don't think mine are, but now I want to figure out how that works. 1600Chips/sec is 600 microseconds per chip. They spin at up to, say, radial rates that are a 100 revs/sec and thus take maybe 10 msec. to travel 30 cm. How much warble in a chip frequency is there?
>
> Ok, maybe they only need to work when the car is stopped.
>
> I would design a tire pressure system that sends, maybe, 10 bits per second, at most. Or calibrate the sensor to produce 1 bit, and use the car metal frame to carry the signal to the computer as a single bit. A very slowly varying sensor can be sensed without needing a battery, by using some passive, tuned circuit.
Well, please poke into it and get back to us. :)
> Bluetooth is way overkill, but cheap. I doubt it works well in the application, though.
I honestly don't know a lot about how it works, I do know that many
tire systems DO use some form of radio, and it's a well described vuln
in several SF novels, in being able to track cars everywhere. It would
be good to *know* how bad the tire sensor problem actually was....
My specific desire to block bluetooth from outside of the car was that
I am perpetually seeing new devices to pair with, that I prefer my
conversation, no matter how theoretically secure it was to not escape,
and that there are all sorts of bluetoothy controls now that someone
could try to take over, and radio interference is a PITA. And my phone
perpetually tries to associate with things I'd rather it not associate
with.
So I could certainly see a cheap coating making the cockpit more
tempest rated being a win. "Available in 2020 from a Tesla dealer near
you!"
My car was built in 2003 and doesn't have any of this newfangled stuff.
> -----Original
> From: "David Lang" <[email protected]>
> Sent: Mon, Nov 19, 2018 at 9:12 pm
> To: "Dave Taht" <[email protected]>
> Cc: "Dave Taht" <[email protected]>, "Rajkumar Manoharan" <[email protected]>, "Make-Wifi-fast" <[email protected]>, "linux-wireless" <[email protected]>, "ath10k" <[email protected]>, "Ben Greear" <[email protected]>, "Felix Fietkau" <[email protected]>
> Subject: Re: [Make-wifi-fast] [PATCH v3 3/6] mac80211: Add airtimeaccounting and scheduling to TXQs
>
> On Mon, 19 Nov 2018, Dave Taht wrote:
>
> >> I'm not sure if this was a fluke or not, but at Starbucks recently I sat outside,
> >> right next to their window, and could not scan their AP at all. Previously, I sat
> >> inside, 3 feet away through the glass, and got great signal. I wonder what that was
> >> all about! Maybe special tinting that blocks RF? Or just dumb luck of some sort.
> >
> > Ya know, I could definitely see a market for a material like that! I'd
> > like it for my car, so bluetooth wouldn't escape.
>
> That would break your tire pressure sensors (each car is rolling around
> broadcasting 4 unique bluetooth IDs, not hard to track)
>
> David Lang
> _______________________________________________
> Make-wifi-fast mailing list
> [email protected]
> https://lists.bufferbloat.net/listinfo/make-wifi-fast
>
--
Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740
its not bluetooth. active tire pressure control systems are based on 433
mhz in most countries. in the usa its 315 mhz
Sebastian
Am 21.11.2018 um 16:28 schrieb David P. Reed:
> Really? Tires are Bluetooth? I don't think mine are, but now I want to figure out how that works. 1600Chips/sec is 600 microseconds per chip. They spin at up to, say, radial rates that are a 100 revs/sec and thus take maybe 10 msec. to travel 30 cm. How much warble in a chip frequency is there?
>
> Ok, maybe they only need to work when the car is stopped.
>
> I would design a tire pressure system that sends, maybe, 10 bits per second, at most. Or calibrate the sensor to produce 1 bit, and use the car metal frame to carry the signal to the computer as a single bit. A very slowly varying sensor can be sensed without needing a battery, by using some passive, tuned circuit.
>
> Bluetooth is way overkill, but cheap. I doubt it works well in the application, though.
>
> -----Original
> From: "David Lang" <[email protected]>
> Sent: Mon, Nov 19, 2018 at 9:12 pm
> To: "Dave Taht" <[email protected]>
> Cc: "Dave Taht" <[email protected]>, "Rajkumar Manoharan" <[email protected]>, "Make-Wifi-fast" <[email protected]>, "linux-wireless" <[email protected]>, "ath10k" <[email protected]>, "Ben Greear" <[email protected]>, "Felix Fietkau" <[email protected]>
> Subject: Re: [Make-wifi-fast] [PATCH v3 3/6] mac80211: Add airtimeaccounting and scheduling to TXQs
>
> On Mon, 19 Nov 2018, Dave Taht wrote:
>
>>> I'm not sure if this was a fluke or not, but at Starbucks recently I sat outside,
>>> right next to their window, and could not scan their AP at all. Previously, I sat
>>> inside, 3 feet away through the glass, and got great signal. I wonder what that was
>>> all about! Maybe special tinting that blocks RF? Or just dumb luck of some sort.
>> Ya know, I could definitely see a market for a material like that! I'd
>> like it for my car, so bluetooth wouldn't escape.
> That would break your tire pressure sensors (each car is rolling around
> broadcasting 4 unique bluetooth IDs, not hard to track)
>
> David Lang
> _______________________________________________
> Make-wifi-fast mailing list
> [email protected]
> https://lists.bufferbloat.net/listinfo/make-wifi-fast
>
>
On Wed, 21 Nov 2018, Sebastian Gottschall wrote:
> its not bluetooth. active tire pressure control systems are based on 433 mhz
> in most countries. in the usa its 315 mhz
Thanks for the correction. My off-hand comment has sure spurred an intersting
side-thread.
David Lang