STM32F417 + XPT2046 (touch screen)

[Antoine Wajntraub]

Posted on February 23, 2017 at 22:57

Hello everyone !

To give you some context : I have a entire project generated by CubeMX on STM32F417, and now, I'm trying to make my touch screen work with it, trough SPI. So far, I can get the IRQ signal, so I detect when I have a touch, but I'm also trying to have the position of the touch, and this is the moment I have a problem.

Every pins are initialized by the code generated by CubeMX, and it's the same for my SPI_Handle.

I saw 'many' examples on the web, most of them they communicate with the functions SPI_I2S_Send/ReceiveData that is normally in the STM32F4XX_StdPeriph_Driver library. But CubeMX didn't generated this library, instead I have the HAL library, with the SPI file, and as I think that CubeMX is not bad, I think that if I don't have the first one, it's because I don't need it. Anyway, I'm trying to make it work with what I have, but I always got the same data, which is not good... Here is the interesting part of my code :

void Touch_GetTouch(uint16_t * xPos, uint16_t * yPos)

{    uint32_t avgX = 0;    uint32_t avgY = 0;    float calX, calY;    TOUCH_CS_RESET;    avgX = Touch_Read(CHX); //0x90    avgY = Touch_ReadY(CHY); //0xD0    TOUCH_CS_SET;    calX = aX * avgX + bX * avgY + dX;    calY = aY * avgX + bY * avgY + dY;    *xPos = calX;    *yPos = calY;}

uint16_t Touch_Read(uint8_t cmd)

{    Touch_Lock();    Touch_Write(cmd);    LCD_Delay(10);    Touch_Unlock();    return Touch_Read();}

uint16_t Touch_Read(void)

{    uint32_t buf;    HAL_StatusTypeDef res;    uint8_t temp;    uint8_t data = 0;    /* Wait for SPI3 Tx buffer empty */    while (hspi2.State != HAL_SPI_STATE_READY);    res = HAL_SPI_Transmit(&hspi2, &data, 1, 500);    if (res == HAL_OK) {        while (hspi2.State != HAL_SPI_STATE_READY);        res = HAL_SPI_Receive(&hspi2, &temp, 1, 500);    }    if (res == HAL_OK) {        buf=temp<<8;        LCD_Delay(1);        while (hspi2.State != HAL_SPI_STATE_READY);        res = HAL_SPI_Transmit(&hspi2, &data, 1, 500);    }    if (res == HAL_OK) {        while (hspi2.State != HAL_SPI_STATE_READY);        res = HAL_SPI_Receive(&hspi2, &temp, 1, 1000);    }    if (res == HAL_OK) {        buf |= temp;        buf>>=3;        buf&=0xfff;        return buf;    }    return buf;

}

void Touch_Write(uint8_t out)

{    while (hspi2.State != HAL_SPI_STATE_READY);    HAL_SPI_Transmit(&hspi2, &out, 1, 500);    while (hspi2.State != HAL_SPI_STATE_READY);    HAL_SPI_Receive(&hspi2, &out, 1, 500);}

 The Touch_Write and Touch_Read are inspired from some projects I saw, like this one :

http://fabioangeletti.altervista.org/blog/stm32f4-discovery-lcd-touchscreen/

I'm a beginner with the SPI, and most of the STM libraries, so I'm probably missing something stupid and simple, but after two days of trying to find that positions, I can't find out what it is.

Thanks for your help, if you need any infos, no problem !

Antoine

#xpt2046 #stm32f4