touch.c File Reference

#include "touch.h"
#include "glcd.h"
#include "power.h"
#include <LPC17xx.h>
#include <stdbool.h>
#include <stdlib.h>

Go to the source code of this file.

Classes
struct	TP_CalibrationMatrix

Macros
#define	TP_CS(a)   ((a) ? (LPC_GPIO0->FIOSET = (1 << 6)) : (LPC_GPIO0->FIOCLR = (1 << 6)))
#define	TP_INT_IN   (LPC_GPIO2->FIOPIN & (1 << 13))
#define	SPI_SPEED_4MHz   18 /* 4MHz */
#define	SPI_SPEED_2MHz   36 /* 2MHz */
#define	SPI_SPEED_1MHz   72 /* 1MHz */
#define	SPI_SPEED_500kHz   144 /* 500kHz */
#define	SPI_SPEED_400kHz   180 /* 400kHz */
#define	THRESHOLD   2
#define	SSP_SR_RECV_FIFO_NOT_EMPTY   2
#define	SSP_SR_BUSY   4
#define	WAIT_IF_BUSY   while (LPC_SSP1->SR & (1 << SSP_SR_BUSY))
#define	CHX   0x90
#define	CHY   0xd0
#define	ABS(x)   ((x) < 0 ? -(x) : (x))

Functions
_PRIVATE void	delay_us (u32 count)
	Delays for the specified number of microseconds.
_PRIVATE void	spi_set_speed (u8 speed)
	Sets SPI speed to the specified value.
_PRIVATE u8	spi_send_command (u8 cmd)
	Writes a command to the ADS7843 trough SSP1 and returns the received byte.
_PRIVATE void	spi_init (void)
	Initializes the SPI interface for ADS7843.
_PRIVATE u16	ads7843_read_adc (void)
	Communicate (via SPI) with ADS7843 and read a 12-bit ADC (Analog to Digital Converter) value.
_PRIVATE u16	ads7843_read_x (void)
	Reads the X coordinate from the touch panel.
_PRIVATE u16	ads7843_read_y (void)
	Reads the Y coordinate from the touch panel.
_PRIVATE void	get_xy (u16 *out_x, u16 *out_y)
	Returns the X, Y coordinates of the touched point.
_PRIVATE bool	poll_touch (TP_Coordinate *out_tp_coords)
_PRIVATE void	draw_calibration_cross (u16 x, u16 y)
_PRIVATE void	delete_calibration_cross (void)
_PRIVATE bool	calc_calibration_matrix (TP_CalibrationMatrix *out_matrix, const LCD_Coordinate *const lcd_3points, const TP_Coordinate *const tp_3points)
bool	calibrate (void)
void	TP_Init (bool skip_calibration)
	Initializes the touch panel.
bool	TP_IsInitialized (void)
bool	TP_IsCalibrated (void)
void	TP_Calibrate (void)
	Blocks until calibration is completed successfully.
const TP_Coordinate *	TP_WaitForTouch (void)
	Blocks until a touch event is detected.
const LCD_Coordinate *	TP_GetLCDCoordinateFor (const TP_Coordinate *const tp_point)
	Converts the touch panel coordinates to LCD coordinates.
TP_ButtonArea	TP_AssignButtonArea (LCD_Button button, LCD_Coordinate pos)
	Assigns a button area to the given button.
void	TP_WaitForButtonPress (TP_ButtonArea button)
	Blocks until the given button area is pressed.
bool	TP_HasButtonBeenPressed (TP_ButtonArea button, const TP_Coordinate *const touch_point)
	Checks if the given button area has been pressed during the touch event which occurred at the given touch point.

Variables
_PRIVATE TP_CalibrationMatrix	current_calib_matrix
	Current calibration matrix.
_PRIVATE bool	initialized = false
_PRIVATE bool	calibratated = false
_PRIVATE LCD_ObjID	calib_cross_obj_id

Macro Definition Documentation

ABS

#define ABS

(

x

)

((x) < 0 ? -(x) : (x))

Definition at line 34 of file touch.c.

CHX

#define CHX   0x90

Definition at line 30 of file touch.c.

CHY

#define CHY   0xd0

Definition at line 31 of file touch.c.

SPI_SPEED_1MHz

#define SPI_SPEED_1MHz   72 /* 1MHz */

Definition at line 15 of file touch.c.

SPI_SPEED_2MHz

#define SPI_SPEED_2MHz   36 /* 2MHz */

Definition at line 14 of file touch.c.

SPI_SPEED_400kHz

#define SPI_SPEED_400kHz   180 /* 400kHz */

Definition at line 17 of file touch.c.

SPI_SPEED_4MHz

#define SPI_SPEED_4MHz   18 /* 4MHz */

Definition at line 13 of file touch.c.

SPI_SPEED_500kHz

#define SPI_SPEED_500kHz   144 /* 500kHz */

Definition at line 16 of file touch.c.

SSP_SR_BUSY

#define SSP_SR_BUSY   4

Definition at line 24 of file touch.c.

SSP_SR_RECV_FIFO_NOT_EMPTY

#define SSP_SR_RECV_FIFO_NOT_EMPTY   2

Definition at line 23 of file touch.c.

THRESHOLD

#define THRESHOLD   2

Definition at line 19 of file touch.c.

TP_CS

#define TP_CS

(

a

)

((a) ? (LPC_GPIO0->FIOSET = (1 << 6)) : (LPC_GPIO0->FIOCLR = (1 << 6)))

Definition at line 9 of file touch.c.

TP_INT_IN

#define TP_INT_IN   (LPC_GPIO2->FIOPIN & (1 << 13))

Definition at line 10 of file touch.c.

WAIT_IF_BUSY

#define WAIT_IF_BUSY   while (LPC_SSP1->SR & (1 << SSP_SR_BUSY))

Definition at line 27 of file touch.c.

Function Documentation

ads7843_read_adc()

_PRIVATE u16 ads7843_read_adc

(

void

)

Communicate (via SPI) with ADS7843 and read a 12-bit ADC (Analog to Digital Converter) value.

Note

This function implements the protocol specification that the device uses.

Definition at line 128 of file touch.c.

{
    u16 buf, tmp;
 
    tmp = spi_send_command(0x00);
    buf = tmp << 8; // Read first 8 bits of the ADC result
 
    delay_us(1); // Wait for the next byte to be ready
 
    tmp = spi_send_command(0x00);
    buf |= tmp; // Read the last 8 bytes of the ADC result
 
    // ADC result is a 12-bit value transmitted as a 16 bit with 4 bits of padding.
    // Need to discard those extra LSBs and return the 12-bit value (& 0xFFF).
    return (buf >> 4) & 0xFFF;
}

ads7843_read_x()

_PRIVATE u16 ads7843_read_x

(

void

)

Reads the X coordinate from the touch panel.

Returns

The 12-bit ADC value of the X coordinate.

Definition at line 147 of file touch.c.

{
    TP_CS(0);
    delay_us(1);
    spi_send_command(CHX);
    delay_us(1);
 
    const u16 adc = ads7843_read_adc();
    TP_CS(1);
    return adc;
}

ads7843_read_y()

_PRIVATE u16 ads7843_read_y

(

void

)

Reads the Y coordinate from the touch panel.

Returns

The 12-bit ADC value of the Y coordinate.

Definition at line 161 of file touch.c.

{
    TP_CS(0);
    delay_us(1);
    spi_send_command(CHY);
    delay_us(1);
 
    const u16 adc = ads7843_read_adc();
    TP_CS(1);
    return adc;
}

calc_calibration_matrix()

_PRIVATE bool calc_calibration_matrix	(	TP_CalibrationMatrix *	out_matrix,
		const LCD_Coordinate *const	lcd_3points,
		const TP_Coordinate *const	tp_3points
	)

Definition at line 290 of file touch.c.

{
    if (!lcd_3points || !tp_3points || !out_matrix)
        return false;
 
    long double divider = ((tp_3points[0].x - tp_3points[2].x) * (tp_3points[1].y - tp_3points[2].y)) -
                          ((tp_3points[1].x - tp_3points[2].x) * (tp_3points[0].y - tp_3points[2].y));
    if (divider == 0)
        return false;
 
    out_matrix->divider = divider;
    out_matrix->a_n = ((lcd_3points[0].x - lcd_3points[2].x) * (tp_3points[1].y - tp_3points[2].y)) -
                      ((lcd_3points[1].x - lcd_3points[2].x) * (tp_3points[0].y - tp_3points[2].y));
    out_matrix->b_n = ((tp_3points[0].x - tp_3points[2].x) * (lcd_3points[1].x - lcd_3points[2].x)) -
                      ((lcd_3points[0].x - lcd_3points[2].x) * (tp_3points[1].x - tp_3points[2].x));
    out_matrix->c_n = (tp_3points[2].x * lcd_3points[1].x - tp_3points[1].x * lcd_3points[2].x) * tp_3points[0].y +
                      (tp_3points[0].x * lcd_3points[2].x - tp_3points[2].x * lcd_3points[0].x) * tp_3points[1].y +
                      (tp_3points[1].x * lcd_3points[0].x - tp_3points[0].x * lcd_3points[1].x) * tp_3points[2].y;
    out_matrix->d_n = ((lcd_3points[0].y - lcd_3points[2].y) * (tp_3points[1].y - tp_3points[2].y)) -
                      ((lcd_3points[1].y - lcd_3points[2].y) * (tp_3points[0].y - tp_3points[2].y));
    out_matrix->e_n = ((tp_3points[0].x - tp_3points[2].x) * (lcd_3points[1].y - lcd_3points[2].y)) -
                      ((lcd_3points[0].y - lcd_3points[2].y) * (tp_3points[1].x - tp_3points[2].x));
    out_matrix->f_n = (tp_3points[2].x * lcd_3points[1].y - tp_3points[1].x * lcd_3points[2].y) * tp_3points[0].y +
                      (tp_3points[0].x * lcd_3points[2].y - tp_3points[2].x * lcd_3points[0].y) * tp_3points[1].y +
                      (tp_3points[1].x * lcd_3points[0].y - tp_3points[0].x * lcd_3points[1].y) * tp_3points[2].y;
 
    return true;
}

calibrate()

bool calibrate

(

void

)

Definition at line 322 of file touch.c.

{
    calibratated = false;
 
    const LCD_Coordinate lcd_crosses[3] = {{45, 45}, {45, 270}, {190, 190}};
    TP_Coordinate tp_crosses[3] = {{0}, {0}, {0}};
 
    if (!LCD_IsInitialized())
        return false;
 
    LCD_SetBackgroundColor(LCD_COL_BLACK, false);
 
    LCD_ObjID text;
    // clang-format off
    LCD_OBJECT(&text, {
        LCD_TEXT2(5, 10, {
            .text = "Touch crosshairs to calibrate",
            .font = LCD_DEF_FONT_SYSTEM,
            .text_color = LCD_COL_WHITE,
            .bg_color = LCD_COL_NONE,
        }),
    });
    // clang-format on
 
    LCD_RMRender();
 
    for (u8 i = 0; i < 3; i++)
    {
#ifdef SIMULATOR
        delay_us(1000 * 50);
#else
        delay_us(1000 * 500);
#endif
 
        draw_calibration_cross(lcd_crosses[i].x, lcd_crosses[i].y);
        const TP_Coordinate *calib_coords = TP_WaitForTouch();
        tp_crosses[i].x = calib_coords->x;
        tp_crosses[i].y = calib_coords->y;
        delete_calibration_cross();
    }
 
    if (!calc_calibration_matrix(&current_calib_matrix, lcd_crosses, tp_crosses))
        return false;
 
    LCD_RMClear();
    calibratated = true;
    return calibratated;
}

delay_us()

_PRIVATE void delay_us

(

u32

count

)

Delays for the specified number of microseconds.

Definition at line 53 of file touch.c.

{
    for (u32 i = 0; i < count; i++)
    {
        u8 us = 12;
        while (us--)
            ;
    }
}

delete_calibration_cross()

_PRIVATE void delete_calibration_cross ( void  )

inline

Definition at line 285 of file touch.c.

{
    LCD_RMRemove(calib_cross_obj_id, false);
}

draw_calibration_cross()

_PRIVATE void draw_calibration_cross ( u16  x, u16  y  )

inline

Definition at line 259 of file touch.c.

{
    // clang-format off
    LCD_OBJECT(&calib_cross_obj_id, {
        LCD_RECT2(x - 15, y - 15, {
            .width = 30,
            .height = 30,
            .edge_color = LCD_COL_WHITE,
            .fill_color = LCD_COL_NONE,
        }),
        LCD_LINE({
            .from = {x, y - 7},
            .to = {x, y + 7},
            .color = LCD_COL_WHITE,
        }),
        LCD_LINE({
            .from = {x - 7, y},
            .to = {x + 7, y},
            .color = LCD_COL_WHITE
        }),
    });
 
    LCD_RMRender();
    // clang-format on
}

get_xy()

_PRIVATE void get_xy	(	u16 *	out_x,
		u16 *	out_y
	)

Returns the X, Y coordinates of the touched point.

Definition at line 176 of file touch.c.

{
    if (!out_x || !out_y)
        return;
 
    const u16 adx = ads7843_read_x();
    delay_us(1);
    const u16 ady = ads7843_read_y();
    *out_x = adx;
    *out_y = ady;
}

poll_touch()

_PRIVATE bool poll_touch

(

TP_Coordinate *

out_tp_coords

)

Definition at line 188 of file touch.c.

{
    if (!out_tp_coords)
        return false;
 
    u16 tp_x, tp_y;
    u16 buffer[2][9] = {{0}, {0}};
 
    u8 count = 0;
    while (!TP_INT_IN && count < 9)
    {
        get_xy(&tp_x, &tp_y);
        buffer[0][count] = tp_x;
        buffer[1][count] = tp_y;
        count++;
    }
 
    if (count != 9)
        return false;
 
    int m0, m1, m2, temp[3];
    temp[0] = (buffer[0][0] + buffer[0][1] + buffer[0][2]) / 3;
    temp[1] = (buffer[0][3] + buffer[0][4] + buffer[0][5]) / 3;
    temp[2] = (buffer[0][6] + buffer[0][7] + buffer[0][8]) / 3;
    m0 = ABS(temp[0] - temp[1]);
    m1 = ABS(temp[1] - temp[2]);
    m2 = ABS(temp[2] - temp[0]);
    if (m0 > THRESHOLD && m1 > THRESHOLD && m2 > THRESHOLD)
        return false;
 
    if (m0 < m1)
    {
        if (m2 < m0)
            out_tp_coords->x = (temp[0] + temp[2]) / 2;
        else
            out_tp_coords->x = (temp[0] + temp[1]) / 2;
    }
    else if (m2 < m1)
        out_tp_coords->x = (temp[0] + temp[2]) / 2;
    else
        out_tp_coords->x = (temp[1] + temp[2]) / 2;
 
    temp[0] = (buffer[1][0] + buffer[1][1] + buffer[1][2]) / 3;
    temp[1] = (buffer[1][3] + buffer[1][4] + buffer[1][5]) / 3;
    temp[2] = (buffer[1][6] + buffer[1][7] + buffer[1][8]) / 3;
 
    m0 = ABS(temp[0] - temp[1]);
    m1 = ABS(temp[1] - temp[2]);
    m2 = ABS(temp[2] - temp[0]);
    if (m0 > THRESHOLD && m1 > THRESHOLD && m2 > THRESHOLD)
        return false;
 
    if (m0 < m1)
    {
        if (m2 < m0)
            out_tp_coords->y = (temp[0] + temp[2]) / 2;
        else
            out_tp_coords->y = (temp[0] + temp[1]) / 2;
    }
    else if (m2 < m1)
        out_tp_coords->y = (temp[0] + temp[2]) / 2;
    else
        out_tp_coords->y = (temp[1] + temp[2]) / 2;
 
    return true;
}

spi_init()

_PRIVATE void spi_init ( void  )

inline

Initializes the SPI interface for ADS7843.

Definition at line 95 of file touch.c.

{
    // Enabling power to SSP1 interface (Synchronous Serial Port), which provides SPI capability.
    POWER_TurnOnPeripheral(POW_PCSSP1);
 
    // P0.7 SCK, P0.8 MISO, P0.9 MOSI are SSP pins.
    LPC_PINCON->PINSEL0 &= ~((3UL << 14) | (3UL << 16) | (3UL << 18)); // P0.7, P0.8, P0.9 cleared
    LPC_PINCON->PINSEL0 |= (2UL << 14) | (2UL << 16) | (2UL << 18);    // P0.7 SCK1, P0.8 MISO1, P0.9 MOSI1
 
    // Setting clock speed for SSP1. 01 = CCLK
    LPC_SC->PCLKSEL0 &= ~(3 << 20); /* PCLKSP0 = CCLK/4 (18MHz) */
    LPC_SC->PCLKSEL0 |= (1 << 20);  /* PCLKSP0 = CCLK   (72MHz) */
 
    // Register Table: User Manual @ Table 370/371
    // CPOL = Clock Polarity / CPHA = Clock Phase
    LPC_SSP1->CR0 = 0x0007; // 8Bit, CPOL=0, CPHA=0 (Control Register 0, clock rate, data size...)
    LPC_SSP1->CR1 = 0x0002; // SSP1 enable, master (Control Register 1, master/slave...)
 
    // SPI communication speed needs to be known and fixed.
    spi_set_speed(SPI_SPEED_500kHz);
 
    // Wait, maybe touch panel is busy
    WAIT_IF_BUSY;
 
    // Consume eventual data in RX FIFO, so that we can start fresh.
    while (LPC_SSP1->SR & (1 << SSP_SR_RECV_FIFO_NOT_EMPTY))
        LPC_SSP1->DR;
}

spi_send_command()

_PRIVATE u8 spi_send_command ( u8  cmd )

inline

Writes a command to the ADS7843 trough SSP1 and returns the received byte.

Parameters

cmd	The command to write to the ADS7843.

Returns

The byte received from the ADS7843.

Definition at line 79 of file touch.c.

{
    WAIT_IF_BUSY;
    LPC_SSP1->DR = cmd; // Write command to the SSP1 data register (R/W)
    WAIT_IF_BUSY;
 
    // Controller should now respond with a byte. It will put it in the RX FIFO.
    while (!(LPC_SSP1->SR & (1 << SSP_SR_RECV_FIFO_NOT_EMPTY)))
        ; // Wait until RX FIFO is not empty
 
    // If here, FIFO contains something, reading it
    const u8 byte_returned = LPC_SSP1->DR;
    return byte_returned;
}

spi_set_speed()

_PRIVATE void spi_set_speed ( u8  speed )

inline

Sets SPI speed to the specified value.

Definition at line 66 of file touch.c.

{
    speed &= 0xFE; // Make sure that speed is even.
    if (speed < 2)
        speed = 2;
 
    // Setting clock prescale register to the desired speed.
    LPC_SSP1->CPSR = speed;
}

TP_AssignButtonArea()

TP_ButtonArea TP_AssignButtonArea	(	LCD_Button	button,
		LCD_Coordinate	pos
	)

Assigns a button area to the given button.

Parameters

button	The button to assign the area to.
pos	The position of the button.

Returns

The button area.

Definition at line 436 of file touch.c.

{
    const LCD_Obj obj = {
        .comps_size = 1,
        .comps =
            (LCD_Component[]){
                (LCD_Component){
                    .type = LCD_COMP_BUTTON,
                    .pos = pos,
                    .object.button = &button,
                },
            },
    };
 
    LCD_BBox bbox;
    if (LCD_CalcBBoxForObject(&obj, &bbox) != LCD_ERR_OK)
    {
        return (TP_ButtonArea){0};
    }
 
    return (TP_ButtonArea){
        .pos = pos,
        .width = abs(bbox.bottom_right.x - bbox.top_left.x),
        .height = abs(bbox.bottom_right.y - bbox.top_left.y),
    };
}

TP_Calibrate()

void TP_Calibrate

(

void

)

Blocks until calibration is completed successfully.

Note

This function is automatically called if skip_calibration is false in TP_Init.

Definition at line 399 of file touch.c.

{
    if (!initialized)
        return;
 
    while (!calibrate())
        ;
}

TP_GetLCDCoordinateFor()

const LCD_Coordinate * TP_GetLCDCoordinateFor

(

const TP_Coordinate *const

tp_point

)

Converts the touch panel coordinates to LCD coordinates.

Parameters

tp_point

The touch panel coordinates.

Returns

The LCD coordinates, or NULL if either the touch panel is not initialized or tp_point = NULL.

Definition at line 419 of file touch.c.

{
    if (!initialized || !tp_point)
        return NULL;
 
    static LCD_Coordinate lcd_point;
    TP_CalibrationMatrix matrix = current_calib_matrix;
    if (matrix.divider == 0 || !tp_point)
        return NULL;
 
    lcd_point.x = ((matrix.a_n * tp_point->x) + (matrix.b_n * tp_point->y) + matrix.c_n) / matrix.divider;
    lcd_point.y = ((matrix.d_n * tp_point->x) + (matrix.e_n * tp_point->y) + matrix.f_n) / matrix.divider;
    return &lcd_point;
}

TP_HasButtonBeenPressed()

bool TP_HasButtonBeenPressed	(	TP_ButtonArea	button,
		const TP_Coordinate *const	touch_point
	)

Checks if the given button area has been pressed during the touch event which occurred at the given touch point.

Parameters

button	The button to check.
touch_point	The touch point to check.

Returns

True if the button has been pressed, false otherwise.

Definition at line 475 of file touch.c.

{
    if (!touch_point)
        return false;
 
    // We should map the coordinates to the LCD coordinates, because the buttons pos
    // is in LCD coordinates!
    const LCD_Coordinate *touch_lcd_pos = TP_GetLCDCoordinateFor(touch_point);
    if (!touch_lcd_pos)
        return false;
 
    const bool between_w = IS_BETWEEN_EQ(touch_lcd_pos->x, button.pos.x + 1, button.pos.x + button.width - 1);
    const bool between_h = IS_BETWEEN_EQ(touch_lcd_pos->y, button.pos.y + 1, button.pos.y + button.height - 1);
    return between_w && between_h;
}

TP_Init()

void TP_Init

(

bool

skip_calibration

)

Initializes the touch panel.

Parameters

skip_calibration

If true, calibration is skipped.

Note

If you skip calibration, the TP_WaitForTouch() could return incorrect values.

Definition at line 373 of file touch.c.

{
    LPC_GPIO0->FIODIR |= (1 << 6);  // P0.6 CS is output
    LPC_GPIO2->FIODIR |= (0 << 13); // P2.13 TP_INT is input
    TP_CS(1);
 
    spi_init(); // Initialize SPI interface for touch panel
    initialized = true;
 
    if (skip_calibration)
        return;
 
    TP_Calibrate();
    // assert(calibratated && initialized); // Should never fail.
}

TP_IsCalibrated()

bool TP_IsCalibrated

(

void

)

Definition at line 394 of file touch.c.

{
    return calibratated;
}

TP_IsInitialized()

bool TP_IsInitialized

(

void

)

Definition at line 389 of file touch.c.

{
    return initialized;
}

TP_WaitForButtonPress()

void TP_WaitForButtonPress

(

TP_ButtonArea

button

)

Blocks until the given button area is pressed.

Parameters

button

The button to wait for.

Definition at line 463 of file touch.c.

{
    if (!initialized)
        return;
 
    TP_Coordinate *touch_point;
    do
    {
        touch_point = (TP_Coordinate *)TP_WaitForTouch();
    } while (!TP_HasButtonBeenPressed(button, touch_point));
}

TP_WaitForTouch()

const TP_Coordinate * TP_WaitForTouch

(

void

)

Blocks until a touch event is detected.

Returns

The X, Y coordinates of the touched point, or NULL if the touch panel is not initialized.

Note

If you call this function without first calibrating the panel, the returned value may be incorrect.

Definition at line 408 of file touch.c.

{
    if (!initialized)
        return NULL;
 
    static TP_Coordinate tp_coords;
    while (!poll_touch(&tp_coords))
        ;
    return &tp_coords;
}

Variable Documentation

calib_cross_obj_id

_PRIVATE LCD_ObjID calib_cross_obj_id

Definition at line 257 of file touch.c.

calibratated

_PRIVATE bool calibratated = false

Definition at line 48 of file touch.c.

current_calib_matrix

_PRIVATE TP_CalibrationMatrix current_calib_matrix

Current calibration matrix.

Definition at line 46 of file touch.c.

initialized

_PRIVATE bool initialized = false

Definition at line 48 of file touch.c.