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TM4C123GH6PZ: 3.5 TFT LCD Touch Screen Problem

Part Number: TM4C123GH6PZ

hello,

I am working on tinylcd's 3.5 TFT Lcd with touch screen, the lcd is working fine but the touch is not working properly.

the part number of lcd is TL03503200480E. Any help would be greatly appreciated.

thank you

  • Hi,
    What do you mean it is not working properly? Is it not working at all or only partially working? Do you have another LCD that you can try? Do they all exhibit the same symptom? If other LCD displays are working fine then it is an isolated hardware issue. You might need to contact your LCD vendor. If all displays exhibit the same symptom then I will suggest from hardware point of view, double check the interface between the MCU and the LCD. What interface is used between the two? Is it SPI? Any other control/handshake signals between the two? Do all the signals meet the timing requirements from the LCD display? From software point of view check if you are the correct commands sent to the display to activate the touch feature. Check the datasheet of the display if you have met all timing requirements. These are some of the suggestions and I/m not familiar with the TL03503200480E display.
  • As you note the "Lcd" as "Tiny" - might your "Not so Tiny" finger - confuse/confound the screen's "Touch-Sense" mechanism?

    it is usual that such screens require strategic, "drive signals" in which "Only one touch plane is Enabled for "READ"" - while its orthogonal "neighbor" is voltage driven - such that the "touch plane" may be read.

    After a given interval that situation (almost exactly) reverses - and the 2nd screen is then "read."

    This is (highly) unlikely to be an MCU based challenge - it is (very much) an LCD Vendor issue - they should receive your (probing/questioning) report...

  • Hi,
    thank you for your valid suggestion. I have interfaced the LCD with SPI protocol, the Lcd is working fine i'm able to change color and write characters onto it. But the touch screen part is not working properly, what I mean to say is during calibration of the touch screen when I touch the screen it is getting calibrated but after that when I touch the screen nothing is happening. And unfortunately I don't have another LCD with me, I asked the Provider for the data sheet but they are not providing it instead they are just sending me the electrical characteristics and timing diagram, thinking to call them directly.
    Anyways thanks for your Suggestion, much appreciated.

    thank you
  • Hi,
    I am using the touch pen they provided, but sill it's not working. I'll call them and tell this is what happening. Thank you for your suggestion.
  • You haven't noted the "type" of touch screen - there are several types. I'd suspect that yours is "Resistive" - an upgrade would be "Capacitive" - yet that's usually more expensive - and more difficult to control.

    You note "SPI" as the interface for the display - yet there (still) is no mention of the "interface to the Touch Screen."      (You clearly can touch/see your device - we helpers do not have that luxury - we "rely upon you to properly describe" - & provide such (needed) facts.

    You write, "During calibration ... when you touch it ... "it IS getting calibrated."      Yet - "How do you know that?"     Most such "calibrations" require a minimum of three "Touch Points" - sometimes that extends to five.

    After such "calibration" - the effectiveness of that calibration is gleaned by your "Touching" several strategic screen points - and then confirming that the Touch Data supplied - is w/in specification.     As you cannot (yet) "Read your Screen" - it is difficult to justify your claim of "proper calibration!"

    Most Resistive (low cost) such screens employ a "four-wire interface." You should be able to "follow the tiny (and transparent) "ITO" traces - and identify the four Touch Interface signal entry points.    (most always 2 will attach to the "left & right" screen edges - the other 2 attach to the "top & bottom" edges.)  

    You may monitor those 2 signals (vertical or horizontal) - noting that one signal will "switch to ground - the other will supply source voltage."       And - as stated earlier - these signals will "cycle" - with (at any particular time) one pair being voltage providing - the second pair providing an analog voltage - reflective of the (actual) screen touch point.

    Now you may have a "Touch Controller" - but if the screen is Resistive - it MUST work as just detailed...     The Touch Controller will "intercept" the analog voltage from the "Non-Driven Plane" - and output that via (usually) a serial interface.       It then "becomes your job" to "Read the Touch Controller" which should provide (both) "X & Y" Plane position info.

    While it IS tempting to "purchase" highly discounted devices - such vendors rarely display the required "skill or caring" - which "Drive your project to Success!"     (And it is likely that you'll "never/ever" be able to buy that "exact" screen - again...)