2.4 inch 4 wire touch panel

External hardware connected to the STM32 board
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ag123
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2.4 inch 4 wire touch panel

Post by ag123 » Sat May 13, 2017 5:53 pm

in case any one is looking for some 2.4inch 4 wire resistive touch panel
http://www.ebay.com/sch/i.html?_odkw=no ... h&_sacat=0
i happen to do a search on ebay and found that these 'nokia asha 300' touch panels are relatively abundant on ebay

accordingly it seemed to be a 2.4 inch resistive touch panel given by the specs of nokia asha 300
http://www.gsmarena.com/nokia_asha_300-4279.php

**** note **** i've not verified if these 'nokia asha touch' is after all the same as those generic 4 wire resistive touch, have not found any specs confirming it. if anyone found more information or use it do post your findings about it, if it is indeed a normal 4 wire resistive touch panel. those other than 'nokia asha 300' some of them has a controller chip and they would likely be capacitive touch which for that matter may not have specs available

the tip on interfacing these 4 wire resistive touch panels can be found here
http://www.ti.com/lit/an/slaa384a/slaa384a.pdf
http://www.instructables.com/id/4-Wire- ... h-Arduino/

the good thing with these would be they are simply *resistors*, so u'd not need to mess with another 'controller' chip, but u'd need 4 analog pins (and maybe 1 power pin to connect the panel with a series resistor)
:D
Last edited by ag123 on Sat May 13, 2017 6:17 pm, edited 1 time in total.

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ahull
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Re: 2.4 inch 4 wire touch panel

Post by ahull » Sat May 13, 2017 6:13 pm

Quite a lot of phone digitizers include an integrated controller. For example the S3 digitizer - >

http://www.ebay.com/itm/Front-Touch-Scr ... KwWq5hZhKw

I have a couple of broken digitizers (with broken glass, but still functional) in my junk box now from my recent phone purchases. The thing that makes them difficult to use in my opinion is the lack of information regarding the connectors they are designed to mate with. If we had a reliable source for some of those, it would be relatively simple to create an unterface PCB to add touch to a whole bunch of displays, or even just a trackpad like panel to may projects.

The panels it appears are typically supported by the linux hid-multitouch module, or some other code in kernel/drivers/input/touchscreen so it should be theoretically possible to create a similar module for stm32duino boards based on an understanding of this code.
- Andy Hull -

ag123
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Re: 2.4 inch 4 wire touch panel

Post by ag123 » Sat May 13, 2017 6:21 pm

for the 'standard' 4 wire ones i hope to find those with 'straight through' flat flex connecting wires
http://www.ebay.com/sch/i.html?_odkw=ff ... r&_sacat=0

saw some videos, but i guess it'd still be a pretty challenging task, probably need to work with a big magnifying glass :lol:
https://www.youtube.com/watch?v=gi-44SDc4ds
https://www.youtube.com/watch?v=R698z9QaypY

for the 'android' style touch digitizers there are 2 problems, one of which is that the bundled controller is rarely specified, i'd guess as you have mentioned, one way is to dig through the android kernel source codes. the second problem is the mating connectors also seemed very small and would probably need some propriety smd connectors, both of which are pretty big challenges as otherwise i'd think they would make good capacitive touch panels

in my google searches, it seemed that for some of these capacitive touch controllers, they are literally some arm cortex-m mcus

oh ok the key word to search needed in ebay is "FPC connector" :D
http://www.ebay.com/sch/i.html?_odkw=fp ... r&_sacat=0
http://www.ebay.com/itm/Logic-Board-Bat ... 2495849621
http://www.ebay.com/sch/i.html?_odkw=fp ... i&_sacat=0

i'm thinking as we continue to dig through the parts, one day we may find all the parts needed to assemble an oem android phone :lol:

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ahull
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Re: 2.4 inch 4 wire touch panel

Post by ahull » Sun May 14, 2017 1:15 pm

Typically the touch panel uses this style of connector.

Image

The exact pin spacing and so forth would need to be determined by examining them. The displays + touch are also available and these tend to have the larger connectors which carry the display and touch signals together, so something like these.

Image

.. but here again, you would need to examine them carefully under a microscope to determine the correct connector.

If some enterprising individual in China were to build an arduino shield style breakout board for one of the cheaper capacitive touch + display combinations, then I suspect it would be as popular, or even more popular than those cheap resistive touch displays that litter the pages of ebay.

All it takes is the right price point, and since there is already a huge market for repair parts for phones and cameras the displays themselves just get cheaper and cheaper.
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ag123
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Re: 2.4 inch 4 wire touch panel

Post by ag123 » Sun May 14, 2017 4:45 pm

strictly speaking resistive touch panels aren't cheap at all, and are possibly worse than capacitive touch, the only good thing is that it is just resistors and nothing in between (not sure if it is true for all), this 'bypass' one of the 'headaches' of undocumented touch screen controllers, which is pretty much 'useless' and for the 'maximum' simplicity it'd need to be the 4 wires pure resistive types and they'd need to fit those bland common straight and cheap 'FPC' connectors or adapters, most of the android and iphone capacitive touch ones have 'esoteric' propriety connectors that doesn't fit any of the 'standard looking' ones and the spacing/tolerance are so 'damn' tight u'd need size the conductors and spacing around the width of hair or thinner :lol:

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zoomx
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Re: 2.4 inch 4 wire touch panel

Post by zoomx » Wed May 17, 2017 11:00 am

There is also the touch screen for the Nintendo DS family, it has an horrible connector but you can find it too because it breaks easily, that's why is horrible.

You can find Arduino implementation
http://tronixstuff.com/2010/12/29/tutor ... ch-screen/
As you can see there is a breakout for this touch screen with the horrible connector.

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