Interfacing with a 4-pin Touch Screen Interface
Jim Fouch
Posts: 395
I'm working on interfacing with an Pioneer DVD Navigation system (AVIC_D3)·I'm installing in my truck.
This system allows the display of a video input. I'm going to use a Prop to generate· TV display and feed that into the DVD system.
The System has a 4-pin Touch Screen. When a video signal is being displayed I don't think the system does anything with the touch screen. I'm just wondering how hard it would be to read the position of the touches. I want to do this w/o interfering with the system. I'm only going to use the touch data when MY screens or being displayed.
I have attached a picture of the 4-pin connector.
My plan first is to probe the 4 pins with a scope while running the system. Then, if I can make sense of the signals, would be to read them into the prop with an ADC.
Does this seem doable? Or am I just crazy???
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Jim Fouch
FOUCH SOFTWARE
This system allows the display of a video input. I'm going to use a Prop to generate· TV display and feed that into the DVD system.
The System has a 4-pin Touch Screen. When a video signal is being displayed I don't think the system does anything with the touch screen. I'm just wondering how hard it would be to read the position of the touches. I want to do this w/o interfering with the system. I'm only going to use the touch data when MY screens or being displayed.
I have attached a picture of the 4-pin connector.
My plan first is to probe the 4 pins with a scope while running the system. Then, if I can make sense of the signals, would be to read them into the prop with an ADC.
Does this seem doable? Or am I just crazy???
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Jim Fouch
FOUCH SOFTWARE
Comments
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Paul Baker
Propeller Applications Engineer
Parallax, Inc.
http://forums.parallax.com/showthread.php?p=713258
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Aka: CosmicBob
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E3 = Thought
http://folding.stanford.edu/·- Donating some CPU/GPU downtime just might lead to a cure for cancer! My team stats.
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Timothy D. Swieter
www.brilldea.com·- check out the uOLED-IOC, an I/O expansion for the uOLED-96-PROP
www.tdswieter.com
One little spark of imagination is all it takes for an idea to explode
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E3 = Thought
http://folding.stanford.edu/·- Donating some CPU/GPU downtime just might lead to a cure for cancer! My team stats.
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Jim Fouch
FOUCH SOFTWARE
This signals I’m getting are going to be a bit tricky to read. They are a 5 pulse burst that the amplitude changes with touch position. These pulses run 2ms in width and if the finger is held it will repeat with a 15-20ms pause between bursts.
I'm thinking of having one cog run a MCP3304 to always capture analog from these two inputs. Another cog would use a comparator to trigger a 1ms delayed reading of the Analog values from both X & Y.
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Jim Fouch
FOUCH SOFTWARE
How did you make out with this project? I'm thinking of doing something similar.
Rick
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Jim Fouch
FOUCH SOFTWARE
Looking around for some theory I found the AD note below which describes a 4 wire touch screen.
They are of course trying to sell their ADC. Would a pair of Propeller ADC circuits also work?
http://www.analog.com/library/analogDialogue/archives/35-04/touchscreen/index.html
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http://store.earthlcd.com/LCD-Products/Add-On-Touch-Screen-Kits
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JMH