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bwhiten
Joined: 26 Nov 2003 Posts: 151 Location: Grayson, GA
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Touchscreen basics |
Posted: Wed Sep 12, 2007 6:14 am |
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To eliminate a costly custom front panel with membrane switches I am thinking of using a touchscreen LCD on this pic project. I have written code to scan a keypad before so that is not a concern. My question is: this particular display calls out a "4-wire analog" touchscreen with active regions of top, bottom, left and right. Does this give me 4 possible "touch zones" to place "graphical buttons" in for the user or am I missing something?
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SET
Joined: 15 Nov 2005 Posts: 161 Location: Glasgow, UK
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Posted: Wed Sep 12, 2007 6:58 am |
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It sounds like a resistive screen, where the x-position is one pair of wires and the y is the other. Normally you would use a touch controller IC to translate the x/y resistance changes into digital form. No reason why you couldn't use the PIC ADC to do this instead. |
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libor
Joined: 14 Dec 2004 Posts: 288 Location: Hungary
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Posted: Wed Sep 12, 2007 6:59 am |
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No.
The '4-wire analog' only describes the interface, it has nothing to do with the resolution of the screen.
There are touch screen controllers with '4-wire analog' input up to a theoretical 4096 x 4096 resolution and you can also have the touch pressure value. Like this here: Touchkit. Actual resolution depends on your fingertip's diameter
There are also stand-alone controller ICs for this with a SPI bus and some fancy addtional functions like battery monitoring, temperature, etc. for 2-3 USD. Like this.
You can easily write your own program in a PIC using the built-in ADCs.
Some info about the various (4-wire, 5 wire and 8 wire) resistive touchscreens' theory of operation you can find here
Last edited by libor on Wed Sep 12, 2007 7:18 am; edited 1 time in total |
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bwhiten
Joined: 26 Nov 2003 Posts: 151 Location: Grayson, GA
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Touchscreen basics |
Posted: Wed Sep 12, 2007 7:16 am |
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Thanks for the help. The links explain it well. More complicated than I had thought but not impossible. |
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