This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

CCS/LAUNCHXL-CC3235SF: Kentec QVGA interface simplelink_sdk_lvgl_plugin_3_30_00_06

Part Number: LAUNCHXL-CC3235SF
Other Parts Discussed in Thread: TIDM-1020

Tool/software: Code Composer Studio

Hello,

The reference design TIDM-1020 discusses the changes required to both the Kentec QVGA display and the CC3220 launchpad so that the touchpad will function correctly. The Readme file in KentecTouchwidgets example above does not mention any changes to the Kentec QVGA display, just to the launchpad. I made all of the changes to the launchpad but I do not seem to be able to get past the 'calibrate touchscreen'. I am not sure if I may have burned something out or arced a connection while soldering, the components are very small so it's possible though I did use the exact same form-factor resistors from the BOM. Are the changes to the touchscreen also required for the screen to sense touch in this example?  

  • Hi Sterling,

    Some of the changes to the Kentec BoosterPack were added so the TIDM-1020 design will stack while accommodating the rest of the sensors and BoosterPacks in the system.

    (Edited) The changes you would need to add are to protect the ADC input voltage in section 3.1.4.1.1 of the guide (the Kentec BP outputs 3.3V, but the CC32xx ADC inputs can only accept 1.4V) while still allowing the pin to switch between an ADC input and GPIO output during runtime. I'm not sure why the demo in the plugin did not address this hardware issue. Good catch.

    Best regards,

    Sarah

  • Thank you, I don't quite understand from your edited response.

    Are you saying that I do need to make the changes to the Kentec touch screen as well? The ADC pins are receiving an analog signal and also sending an output signal to the Kentec (total of four outputs, two of which are multiplexed with the ADC pins).

    The Kentec would be sending a total of four analog signals (XP, YP, XN, YN) back to the launchpad but since the launchpad does not have a sufficient number of ADC's, you have this workaround so probably some modifications to the Kentec are still required since the the four ADC's come into different pins on the launchpad? 

    When in debug, the ADC registers are not changing values as I touch the screen, are these the correct registers to be looking at? 

    I want to be sure of this since I don't want to make more changes to a different launchpad. Even though I have the right tools, I don't really want to keep making additional changes to other components until I figure out if my soldering job went okay. 

  • Hi Sterling,

    The Kentec display only requires 2 ADC channels. See section 2.3.1.1 Touch-Position Detection and Touchscreen Calibration of the TIDM-1020 guide for further explanation on the behavior of the 4 pins.

    The important difference is that the 2 ADC pins must be able to toggle between ADC input and GPIO output during runtime. The existing op-amp buffer on those LaunchPad header pins (to protect the ADC from receiving voltages higher than 1.4V and damaging the CC32xx) does not allow the GPIO output to work. In the TIDM-1020, we bypassed the op-amps on the LaunchPad and added a different voltage divider.

    You do not need to make any changes to the Kentec BoosterPack. The only changes that need to be made are to the LaunchPad ADC pins.

    (Sorry for the edit. I originally only remembered the hardware changes done to make the LaunchPads stack. I had forgotten about the fixes we made for the ADC pins.)

    Best regards,

    Sarah