[Arm-netbook] capacitive touchpanels

[Hans-Christian Jehg]

This is truely interesting project :-D

Can't wait to read the next edition.

HC

On Nov 24, 2012, at 20:00, arm-netbook-request at lists.phcomp.co.uk wrote:

> Message: 2
> Date: Sat, 24 Nov 2012 15:18:43 +0000
> From: "luke.leighton" <luke.leighton at gmail.com>
> Subject: [Arm-netbook] capacitive touchpanels
> To: Linux on small ARM machines <arm-netbook at lists.phcomp.co.uk>
> Message-ID:
>    <CAPweEDxmiGzVnacmFP4d7tROg+iswj33a8aqL1ggyii011M-rQ at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
> 
> http://electronics.howstuffworks.com/iphone2.htm
> 
> this is fascinating.  and... well... kinda necesary to investigate.  i
> found out that a decent 7in tablet capacitive panel (5T) is around $22
> to $24.  this is mad prices.  one that has a lot less sensor lines can
> be had *WITHOUT* an on-board controller IC can be had for around $11.
> 
> *but* - the problem with doing that according to wikipedia is stray
> capacitance: http://en.wikipedia.org/wiki/Capacitive_sensing#Circuit_design
> 
> however, given that the price of the controller ICs is absolutely mad
> - i'm seeing prices of $4 (!!) - it's just... i can't bring myself to
> justify it sooooo, the idea is to use a 100-pin STM32F.  15 "scan"
> lines (across the horizontal), and 10 "sensor" lines (going down), i
> feel reasonably confident that this is doable, although, obviously,
> i'm going to have to check!
> 
> what fun, eh?  no proprietary ICs - just use a single controller, do
> it all as free software :)
> 
> l.
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