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STMPE610 - Problem with Touch Detection

Question asked by kokorikos on May 22, 2013
Latest reply on May 24, 2013 by kokorikos
Hi Forum users,
I try to bring in my project all the advantages that a TFT Display with touchscreen promises. The touchscreen controller STMPE610 with the Displaytech's TFT Display, DT028ATFT-TS, is used but unfortunately till now I cannot make it work.The Initialisation commands are sent with I2C and it seems that works fine.
According to the attached schematic "TS-Controller_Circuit.JPG", the IN2 and IN3 are not used and I connected them to the GND with a 10k resistor in between. The capacitors connected to the signal lines TFT_YU, TFT_YD, TFT_XR and TFT_XL are not 2pF but 2.2nF 0603. The interrupt signal TS_INT is connected to an MCU input (R8, pull-up resistor).

Now, getting to the point ... I have measured the following voltages with or without touching the surface
 Vio = 3.28V
 V_XL or V_X- = 3.27V
 V_XR or V_X+ = 0V
 V_YU or V_Y+ = 0V
 V_YD or V_Y- = 0V

and no interrupt is generated. What seems the problem? Probably is my misunderstanding of the controller, so pls could you tell me where I've got it all wrong???

Thanks a lot all of you, in advance!!!

P.S. This is the initialisation code

void STMPE610_Init(void)
    //STMPE610_Write(SYS_CTRL2, 0x0F);     // Disable TSC and ADC Blocks
//    STMPE610_Write(TSC_CTRL, 0x43);     // Enable Touchscreen, 32 points tracking index, X, Y mode
//    __delay_cycles(10);
//    STMPE610_Write(SYS_CTRL1, 0x02);    // Reset Device
//    __delay_cycles(100000);    
    STMPE610_Write(SYS_CTRL2, 0x0C);     // Enable TSC and ADC Blocks
    STMPE610_Write(INT_EN, 0x01);         // TOUCH_DETECT-Interrupt are enabled
    STMPE610_Write(ADC_CTRL1, 0x49);     // 80 clock cycles for ADC conversion, 12-bit ADC and internal ref
    __delay_cycles(10000);               // delay 2ms
    STMPE610_Write(ADC_CTRL2, 0x01);     // ADC Clock = 3.25 MHz
    STMPE610_Write(GPIO_AF, 0x00);
    STMPE610_Write(TSC_CFG, 0x9A);         // Average Control: 4 samples
                                         // Touch detect delay: 500us
                                         // Panel driver settling time: 500us
    STMPE610_Write(FIFO_TH, 0x01);         // Not zero value
    STMPE610_Write(FIFO_STA, 0x01);         // Clear the FIFO Memory Content
    STMPE610_Write(FIFO_STA, 0x00);         // FIFO back to operation mode
    STMPE610_Write(TSC_FRACT_XYZ, 0x07);// Data Format for Z-Value
    STMPE610_Write(TSC_I_DRIVE, 0x01);    // Choose 20mA driving channel
    STMPE610_Write(TSC_CTRL, 0x03);     // Enable Device, No tracking index, X, Y, Z mode
    STMPE610_Write(INT_STA, 0xFF);        // Clear all interrupt status
    STMPE610_Write(INT_CTRL, 0x03);     // Enable the interrupts
    // define initial Touch Window
    /*STMPE610_Write(WDW_TR_X, 0x0FFF);    // Top Right X
    STMPE610_Write(WDW_TR_Y, 0x0FFF);   // Top Right Y
    STMPE610_Write(WDW_BL_X, 0x0000);    // Bottom Left X
    STMPE610_Write(WDW_BL_Y, 0x0000);   // Bottom Left Y