CCS/BOOSTXL-K350QVG-S1: Coordinates of lcd screen

Greetings,

Sheetal Patil said:

How can I get coordinates of any point by touching it?

Much depends upon the presence of a Touch-Screen Controller w/in your Display Kit.   My group will cover (both) cases (those with & without such an external Touch Control IC.)

I. With a Touch Controller:  We've seen these produce the following outputs:

• Voltage measured in each of the orthogonal planes
• Coordinates measured in each plane
• And sometimes - both voltage & coordinates

There are many different Touch Controllers - you must properly review the Touch Controller's Manual to discover its output capabilities. 

II. Without a Touch Controller:  Assuming the API does not satisfy your need:

• It would be "unusual" for you to output such data to your user.   (w/in the final application)   Thus you must implement a "Special SW Mode" which outputs those coordinates upon the receipt of a "Special Command or hardware signal."   That "Coordinate Display Mode" would then persist until you 'Order it to cease.'
• Upon a "touch" it is normal for an interrupt to be generated.   While you are w/in the "Coordinate Display Mode" you would provide a unique code path which would "deviate" from the "normal" Touch Operation - and instead output the Touch Coordinates.
• W/in that interrupt the "raw ADC voltage" of (both) planes can be noted.   (Code should exist which (already) handles that - for both X&Y planes)
• With the ADC voltage known - that data can then be easily scaled/translated to "Display Coordinate Values"
• The final job then is to: "Output that coordinate data to a suitable position upon the Display."

It is likely that a "brief Touch" will produce a transient (very short) ADC voltage detection.   You must insure that your code "Captures & Stores" those voltage readings - so that the remainder of the process "has eased access" to that, Touch-Point  ADC data.

We are assuming that a "4-wire, resistive Touch-Screen is in play!    These force added HW & SW demands upon the MCU:

• it is necessary to, "Power one plane at a time - while "reading the ADC" which is connected to the (other) plane during that process
• upon the above's completion - the 2nd plane is powered & the other (first, now) plane is read

To clarify - two of the 4 wires tie to ground.   These represent the ground "edge" of each plane.   The 2 remaining Touch-Screen connections must serve two roles:

• receive power while the other plane is being read
• then switch to an ADC input

this process continues - and sometimes multiple readings are obtained & then averaged.   It should be clear that, "Reading the Touch Panel's voltage demands a well thought & executed approach."

Add-On (not quite an edit) - Crack Staff notes that there are MANY Code Examples which:

• Configure & then obtains the ADC's Output in its (standard - NON Display Coordinate) form
• and usually outputs such ADC Data to an attached PC via a UART/ICDI combination.   Now in your case - that may (or may not) prove a successful alternative.   (still requires unique SW development on YOUR part!)
• Should you reject the "PC's presentation" then you must "Replace" the UART Output application w/what's been outlined (above).

Our group posted about these "4-wire Touch Panels" a few months earlier - you'd likely benefit from finding & studying that writing...

The ability to "Read the ADC Voltage and present that to an attached Display" is a great asset - and enjoys VALUE FAR beyond the (limited) "touch panel coordinate detection!"   (thus a more general & improved (i.e. REAL SOLUTION!)

Thankyou.

I tried the toggle led code for touchscreen but the touchscreen is not working. The led does not toggle after touching. Is there a problem with my screen because i have used the demo code.

My code is getting stucked in WidgetMessageQueueProcess(). The touch is not sensed. Even I tried using a different lcd still the issue remains the same.

Which demo are you running? Which LaunchPad are your using?

I am running lab10 of Tiva Launchpad workshop. I am using TM4C123GH6PM and lcd is BOOSTXL-K350QVG-S1.

Do you have the R9 and R10 resistors removed on your launchPad? If not, you need to remove them in order to work. 

I have removed R10 initially when the display was not working. Then I was able to display images. I didn't remove R9.

I will remove it and try.

I tried to get the coordinates of the screen, when I am touching at upper left corner technically I should get 0,0 but instead I get x=13, y=1

Even the bottom right corner gives 313,218 which is not correct. Why are the coordinates wrong? Any clue?

I used touch screen interrupt to get the coordinates.

Good that...

Sheetal Patil said:

Now I want to display the coordinates of the screen when I touch a particular point.

Are you stating that your "original goal" (& thread's title - as above) has been achieved?    (somehow - that appears, "Forgotten!")

And ... if that's so - "How do you switch between "Display Coordinate & Normal Touch" Processing?    (Users are unlikely to "welcome" the Coordinate Display w/each/every "Touch!")

[edit]  Your latest post & mine just "crossed."

There should exist a "Calibration Routine" which enables "fine adjustment" of the Touch Screen Coordinate management...   It is (not) unusual for the Touch-Screen's Active Area to exceed the display's pixel field.   Proper software enables you to then, "Capture & Correct" the transmission of "Accurate Screen Coordinates" as you desire.   (i.e. to the Screen or elsewhere...)

Hi,

  On my reply on Tue, Feb 18 2020 9:35 AM I recommend examples such as calibrate. Although this is an example developed for the TM4C129 EVM, you can reference it and port to TM4C123.