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" <david@xxxxxxx>
Sent: Mon, Nov 19, 2018 at 9:12 pm
To: "Dave Taht" <dave.taht@xxxxxxxxx>
Cc: "Dave Taht" <dave.taht@xxxxxxxxx>, "Rajkumar Manoharan" <rmanohar@xxxxxxxxxxxxxx>, "Make-Wifi-fast" <make-wifi-fast@xxxxxxxxxxxxxxxxxxxxx>, "linux-wireless" <linux-wireless@xxxxxxxxxxxxxxx>, "ath10k" <ath10k@xxxxxxxxxxxxxxxxxxx>, "Ben Greear" <greearb@xxxxxxxxxxxxxxx>, "Felix Fietkau" <nbd@xxxxxxxx>
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
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