S3C2440 Test Procedure (V) Touch Screen Experiment

          The detection principle of resistive touch screen is that after touching, the upper and lower conductive layers come into contact, changing the voltage output, and after A/D conversion, it becomes the X, Y coordinates of the point.
          Initialize AD and touch port:
          void TouchSrceen_Test(void)

         {

                rADCDLY = 50000; //(1/3.68MHz)*50000 = 13.56ms
  Note: Before ADC conversion, the external clock X-tal clock: 3.68MHz is used,
                                and then GLK: 50MHz is used

                rADCCON = (1<<14)|(prescaler<<6);

                Note: bit[14]: 0--disable ADC 1--enable ADC bit[13:6]: prescaler = 9 ADC fleq = 50MHz/(9+1) = 5MHz

                Uart_Printf("\nTouch Screen test\n");

                rADCTSC = 0xd3;//waiting for interrupt Mode
  Note: bit[1:0]: 11--waiting for interrupt Mode
   bit[2]: 0--Normal ADC 1--Auto Sequential measurement of X-position,Y-position
   bit[3]: 0--XP pull-up enable 1--XP pull-up disable
   bit[4]: 0--XP output driver enable 1--XP output driver disable
   bit[5]: 0--XM output driver disable 1--XM output driver enable
   bit[6]: 0--YP output driver enable 1--YP output driver disable
   bit[7]: 0--YM output driver disable 1--YM output driver enable
   bit[8 ]: 0--stylus down interrupt signal 1--stylus up interrupt signal

                pISR_ADC = (int)ADC_TCTest;

                rINTMSK = ~(1<<31); //clear ADC MASK bit

                rINTSUBMSK = ~(1<<9); //clear TouchScreen MASK bit

       }

       void __irq ADC_TCTest(void)

       {

                U32 saveADCDLY;

                if(rADCDAT0 & 0x8000) //bit[15]:0--stylus down 1--stylus up

                {

                      rADCTSC &= 0xff; //clear bit[8]:0 stylus down 1--stylus up

                }

                rADCTSC = (1<<3)|(1<<2); //disable XP pull-up

                 //auto sequential measurement of XY position

                saveADCDLY = rADCDLY;

                rADCDLY = 40000; //(1/50MHz)*40000=0.8ms
  Note: As shown in the figure below, switch to GCLK when X,Y conversion is required.

                 rADCCON |= 0x01; //start ADC

                 while(rADCCON & 0x1); //waiting for ADC startup

                 while(!(rADCCON & 0x8000)); //waiting for ADC end

                 while(!(rSRCPND & (0x1<<31)));//waiting for interrupt bit=1

                 xdata = rADCDAT0 & 0x3ff;

                 ydata = rADCDAT1 & 0x3ff;
   Note: Read the X, Y coordinate data in the buffer

                 if(((xdata-xdata_save > 5)||(xdata-xdata_save < -5))\

                 ||((ydata-ydata_save > 5)||(ydata-ydata_save < -5)))

                 {

                         Uart_Printf("X_value = %d,Y_value = %d,X_data = %d,Y_data = %d\n",\
                                        xdata,ydata,xdata_save,ydata_save);

                 }

                 xdata_save = xdata;

                 ydata_save = ydata;

                 
                         rSUBSRCPND |= (1<<9);

                 rINTSUBMSK =~(1<<9);

                 rSRCPND |= (0x1<<31);

                 rINTPND |= (0x1<<31);

                 rINTMSK = ~(0x1<<31);

   Note: Clear all interrupt-related flags to prepare for the next interrupt

                         rADCTSC = 0xd3; //waiting for interrupt

                 rADCTSC |= 0x100; //stylus up

                 while(!(rSUBSRCPND & (1<<9))); //waiting for stylus up interrupt bit=1

 
  Uart_Printf("The pen has stylus up.");

  rSUBSRCPND |= (1<<9);

  rINTSUBMSK =~(1<<9);

  rSRCPND |= (0x1<<31);

  rINTPND |= (0x1<<31);

  rINTMSK = ~(0x1<<31);
  Note: Clear all interrupt-related flags to prepare for the next interrupt

  rADCDLY = saveADCDLY;

  rADCTSC &= ~0x100; //stylus down

}