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Olimex Support Forum

OLinuXino Android / Linux boards and System On Modules => A20 => Topic started by: GadgeurX on March 01, 2020, 11:05:48 PM

Title: A20-SOM Touchscreen CTS
Post by: GadgeurX on March 01, 2020, 11:05:48 PM
Hi all

I just buy a LCD-OLinuXino-5CTS for my A20-SOM board but I'm unable to have the touchscreen working. I thinks it's because the board is in analog interface mode.

Have you any way to put the SOM in digital mode or something else ?

Thanks
Title: Re: A20-SOM Touchscreen CTS
Post by: LubOlimex on March 02, 2020, 09:23:13 AM
Hello,

When using an A20 board and you want to switch between resistive and capactive touch interface, you'd need to perform some hardware re-configuration. For the A20-SOM specifically this is done on the bottom board - A20-SOM-EVB. There are four PCB jumpers that need to be changed. Locate jumpers PH10/TPX1, SCK2/TPY1, PH11/TPX2, SDA2/TPY2 - by default these are set to resistive touch screen operation - TPX1 side, TPY1 side, TPX2 side, TPY2 side. You need to set them to the other position - this is done by disconnecting the original position and soldering the other (cut between the pads of the original position since there is tiny wire, solder together the pads of the new position, test with multimeter for accidental missoldering). So you need to set the jumpers to position PH10, SCK2, PH11, SDA2.

Refer to the schematic of the A20-SOM-EVB (near the LCD connector).

Of course, for your end project, if you design own bottom board, you don't need to install jumpers if you intend to use purely capactive touch screen.
Title: Re: A20-SOM Touchscreen CTS
Post by: GadgeurX on March 03, 2020, 12:45:30 PM
Hi LubOlimex,

Thanks for your reponse, I'm still unable to locate the jumpers on the A20-SOM-EVB schematic. On my side TPX1/2 and TPY1/2 on A20-SOM-EVB are connected right to the same pin on the som board.
I missed something ?
Title: Re: A20-SOM Touchscreen CTS
Post by: LubOlimex on March 03, 2020, 04:06:01 PM
Can you tell me what hardware revision of the A20-SOM-EVB do you have? It seems the GitHub might lack some of the hardware revisions.
Title: Re: A20-SOM Touchscreen CTS
Post by: GadgeurX on March 03, 2020, 04:16:58 PM
I do not have a A20-SOM-EVB, it's just to understand how it's make on the reference board. But I checked on revision C and C1 without success.
Title: Re: A20-SOM Touchscreen CTS
Post by: LubOlimex on March 03, 2020, 04:19:53 PM
Oh, I'd upload newer revisions, it seems like what is available online is older revisions only. The excerpt looks like this: ftp://staging.olimex.com/Lub-clients/revision-f.jpg
Title: Re: A20-SOM Touchscreen CTS
Post by: GadgeurX on March 03, 2020, 04:22:44 PM
Perfect, thanks for your support.
Title: Re: A20-SOM Touchscreen CTS
Post by: LubOlimex on March 03, 2020, 04:34:21 PM
Latest revisions E and F can be found here now:

https://github.com/OLIMEX/SOM/tree/master/A20/A20-SOM-EVB
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