ST AEK-LCD-DT028V1 Manuale utente

Introduction

The AEK-LCD-DT028V1 evaluation board hosts a 2.8” LCD display with resistive touch for a graphical user interface (GUI)

which interacts with SPC58 MCU discovery boards. It aims at providing, in the prototyping phase, a simple and fast tool to

display information or simple menus in automotive applications.

A new trend in modern vehicles calls for several auxiliary displays to complement the main infotainment system. The additional

displays are employed for status feedback reporting, for extended infotainment features like in rear-seats and for basic control to

replace standard buttons and levers like in seat adjustment, mirror positioning or headlight height adjustment.

Figure 1. Extended infotainment system

The board can be easily evaluated thanks to a common platform consisting of SPC5-STUDIO and AutoDevKit (plug-in of

SPC5-STUDIO based on the Eclipse platform). This tool-set facilitates the configuration of the board and the microcontroller

peripherals used and provides automatic code generation capability exploiting a template-based engine.

The AEK-LCD-DT028V1 has a 240x320 pixels LCD resolution and interfaces with an ILI9341 IC driver, managing the display,

and a TSC2046, managing the touch feedback, via SPI communication (4 wires).

Getting started with the AEK-LCD-DT028V1 display expansion board with

resistive touch for Chorus family

UM2939

User manual

UM2939 - Rev 1 - September 2021

For further information contact your local STMicroelectronics sales office. www.st.com

Figure 2. AEK-LCD-DT028V1 evaluation board (top and bottom views)

Warning:

The AEK-LCD-DT028V1 evaluation board has not to be used in a vehicle as it is designed for

R&D laboratory use only.

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UM2939 - Rev 1 page 2/28

1Getting started

1.1 Features

• 2.8 "(240x320 pixel) TFT SPI LCD with resistive touch managed by an SPI touch screen controller available

on the board

• PCB header connector interfacing with SPC5 MCU discovery boards

• 3.3V LDO voltage regulator for I/O signals

• 53 mm x 87 mm

• WEEE and RoHS compliant

1.2 Hardware overview

1.2.1 Display control circuit

The display control circuit is managed by an ILI9341 controller. It is a 262, 144-color single-chip SOC driver used

for a TFT liquid crystal display with a resolution of 240RGBx320 dots, 172,800 bytes GRAM for graphic display

data, and power supply circuit.

The ILI9341 supports different communication protocols such as parallel communication at 8-bit, 9-bit, 16-bit,

18-bit, and SPI communication via three or four wires. It also supports display at 65K, 262K RGB color, display

rotation and scroll view.

In the AEK-LCD-DT028V1 evaluation board, the communication between the ILI9341 and the external

microcontroller is managed via 4-wire SPI communication. Moreover, the ILI9341 controller is configured to work

in 16-bit (RGB565) mode in order to display up to 65K colors per pixel.

Figure 3. SPI communication protocol implemented by ILI9341

CSX can be "H" between

command/command and parameter/command

During CSX = "H", SCL and SDA are invalid

As we can see from the above image, only when the CSX (chip select) is low the communication is enabled and,

depending on the value of D/CX data control pin, the data sent by SDA are interpreted as commands or as data:

when D/CX is high, the SDA data are interpreted by the controller as commands, whereas when it is low, they are

interpreted as data.

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Getting started

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Figure 4. Data Format

1.2.2 Touch control circuit

The touch control circuit is managed by the TSC2046. It is a next-generation version to the ADS7846 4-wire touch

screen controller which supports a low-voltage I/O interface from 1.5 V to 5.25 V. The TSC2046 can detect the

pressed screen location and measure touch screen pressure. The communication between the TSC2046 and the

external microcontroller is performed via SPI.

On the AEK-LCD-DT028V1 evaluation board, every time the TSC2046 detects a touch on the display, it raises

an external interrupt to inform the MCU that a touch event occurred. Then, the MCU sends a request via SPI

communication to the TSC2046 to retrieve the X and Y coordinates related to the touch just detected. The

external interrupt is disabled and low during the measurement cycle for the X and Y coordinates.

Figure 5. SPI communication protocol implemented by TSC2046

Note: (1) For Y position, driver 1 is on when X+ is selected and driver 2 is off. For X position, driver 1 is off, Y+ is

selected and driver 2 is on. Y- turns on when power-down mode is entered and PD0 = 0.

Note: (2) Drivers remain on if PD0 = 1 (power-down mode not activated) until the selected input channel, reference

mode or power-down mode is changed or CS is high.

In the figure above, the source of the digital signals is a microcontroller with a basic serial interface. The

communication between the processor and the converter consists of eight clock cycles. One complete conversion

can be accomplished with three-serial communication, for a total of 24 clock cycles on the DCLK input. The

first eight clock cycles are used to provide the control byte via the DIN pin. When the converter has enough

information, it enters acquisition mode.

The acquisition time is included in the first eight clock cycles while the next twelve clock cycles accomplish the

actual analog to-digital conversion. In AEK-LCD-DT028V1, the TSC2046 is configured to complete the conversion

in thirteen clock cycles. To complete the DOUT replay message, three more clock cycles are needed but they will

be ignored by the converter.

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Hardware overview

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1.2.3 AEK-LCD-DT028V1 pin-out description

Table 1. AEK-LCD-DT028V1 pin-out

Pin Symbol on PCB Description

1 VCC 5 V power supply

2 GND Ground

3 CS Chip select signal

4 RESET Reset control signal

5 WR/DC Data selection control signal

6 MOSI SPI bus master output slave input

7 SCLK SPI clock signal

8 LED LCD back light control signal

9 MISO SPI bus master input slave output

10 T_SCLK Touch screen SPI clock signal

11 T_CS Touch screen chip select signal

12 T_DIN Touch screen SPI bus master output slave input

13 T_DOUT Touch screen SPI bus master input slave output

14 T_PIRQ Touch screen interrupt

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Hardware overview

UM2939 - Rev 1 page 5/28

2AutoDevKit software library for AEK-LCD-DT028V1 board

All the development of the drivers related to the LCD display based on AEK-LCD-DT028V1 are included in a

component belonging to AutoDevKit software (STSW-AUTODEVKIT) version 1.5.0 (or higher).

The library is written in C and the target software is automatically generated according to the code generation and

pin allocation paradigm included in AutoDevKit design flow.

The library implemented to manage the AEK-LCD-DT028V1 board can be divided into:

• Graphic library

• Touch library

2.1 Graphic library

The graphic library implements screen orientation, basic geometric figures (e.g., rectangles, triangles, circles,

lines) and the respective fill functions. It also includes functions dedicated to the visualization of characters and

strings with different fonts and colors.

Figure 6. AEK-LCD-DT028V1 graphic library files

2.2 Touch library

The touch library implements the function to retrieve the X and Y coordinates (not in pixel) of the touched point on

the display and the functions to manage the external interrupt when the touch is detected.

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AutoDevKit software library for AEK-LCD-DT028V1 board

UM2939 - Rev 1 page 6/28

Figure 7. AEK-LCD-DT028V1 touch library files

2.3 Usage of graphic and touch libraries example

This example is based on the assumption that we want to display a menu of four buttons on the AEK-LCD-

DT028V1 LCD as showed in the image below and add an action each time a button is pressed.

Note: This square-shaped approximation could be used also to display more complex images. In this case, the square

would represent the touchable area behind the image.

Figure 8. AEK-LCD-DT028V1 square-shaped touch menu representation

The following steps shows how to create the code required to implement a proper detection of the blue square

(bottom left one).

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Usage of graphic and touch libraries example

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Step 1. Use the graphic library to draw the four squares representing our buttons.

The required driver function is:

aek_ili9341_drawRect(AEK_LCD_DEV0, 10, 80, 105, 110, ILI9341_COLOR_BLUE);

and the input parameters are:

*@brief Draw a Rectangle

*@param[in] dev LCD_Component

*@param[in] x, y top left coordinates

*@param[in] h, w rectangle dimension

*@param[in] color RGB565 color

Step 2. To retrieve the X, Y absolute coordinates of the blue square (bottom left one), touch the vertices of the

blue square one by one in progression.

At every touch detection in the code, a driver function is invoked to read and store the returned position

values. The procedure will be repeated four times to cover all square vertices.

i=0;

for (; ;) {

if (aek_lcd_get_touchFeedback(AEK_LCD_DEV0) != 0U) { // the screen has been

touched

if (i<4) { // we are in calibration phase to identify the blue square

coordinates

aek_lcd_read_touch_pos(AEK_LCD_DEV0, x_value[i], y_value[i]);//store in

the array each vertex position

i++; }//move to next corner

else {

// first time save the extreme corners of the square in the

xx_BlueButton variables

aek_lcd_read_touch_pos(AEK_LCD_DEV0, &x_value. &y_value] // we

are in normal touch detection phase

if ((X)_BlueBotton < x_value && x_value < X1_BlueButton) &&

(Y0_BlueButton< y_value && y_value <

Y1_BlueButton)) { /*do something*/ }

}

// reset the state of LCD Touch in order to detect a new touch.

aek_lcd_set_touchFeedback(AEK_LCD_DEV0)

}

The input parameters of the aek_lcd_read_touch_pos() function are:

*@param[in] dev LCD_Component

*@param[in] x coordinate x read

*@param[in] y coordinate y read

The blue square touching area is now identified.We Once received, we read the new position detected

and we compare it with the xx_BlueBotton variables to verify if the touch is on the blue square.

Step 3. To test if the touches are inside or outside the blue square, store the extreme corner of the square in

four xx_BlueBotton variables and wait for the next touch event ("else" case of the above code).

if((X0_BlueButton < x_value && x_value < X1_BlueButton) && (Y0_BlueButton <

y_value && y_value < Y1_BlueButton))

{

// do something

}

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Usage of graphic and touch libraries example

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3AutoDevKit ecosystem

The application development employing the AEK-LCD-DT028V1 takes full advantage of the AutoDevKit

ecosystem, whose basic components are:

•SPC5-STUDIO integrated development environment (IDE)

• PLS UDE programmer and debugger

• AutoDevKit software library (STSW-AUTODEVKIT)

• AEK-LCD-DT028V1 driver

3.1 SPC5-STUDIO

SPC5-STUDIO is an integrated development environment (IDE) based on Eclipse designed to assist the

development of embedded applications based on SPC5 Power Architecture 32-bit microcontrollers.

The package includes an application wizard to initiate projects with all the relevant components and key elements

required to generate the final application source code. It also contains straightforward software examples for each

MCU peripheral.

SPC5-STUDIO also features:

• the possibility of integrating other software products from the standard Eclipse marketplace

• free license GCC GNU C Compiler component

• support for industry-standard compilers

• support for multi-core microcontrollers

• PinMap editor to facilitate MCU pin configuration

Note: You need to download the SPC5-UDESTK-SW software to run and debug applications created with SPC5-

STUDIO.

3.2 STSW-AUTODEVKIT

The STSW-AUTODEVKIT plug-in for Eclipse extends SPC5-STUDIO for automotive and transportation

applications.

STSW-AUTODEVKIT features:

• integrated hardware and software components, component compatibility checking, and MCU and peripheral

configuration tools

• the possibility of creating new system solutions from existing ones by adding or removing compatible

function boards

• new code can be generated immediately for any compatible MCU

• high-level application APIs to control each functional component, including the ones for the AEK-LCD-

DT028V1 board

The GUI helps configure interfaces, including SPI, and can automatically manage all relevant pin allocation and

deallocation operations.

For more information, refer to UM2623 (in particular, Section 6 and Section 7) or watch the video tutorials.

3.3 AEK_LCD_DT028V1 component

The AEK-LCD-DT028V1 evaluation board drivers are provided with the STSW-AUTODEVKIT (from version 1.5.0

on) installation to facilitate the programming phase.

Update your AutoDevKit installation to get the latest version. Once properly installed, you will be able to select the

component named AEK_LCD_DT028V1 Component RLA.

3.3.1 AEK_LCD_DT028V1 component configuration

To configure the component, follow the procedure below.

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AutoDevKit ecosystem

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Step 1. Select the font file to be embedded into your application.

Figure 9. Selecting the font size file

Step 2. Add a row (by clicking on the + sign) in the board list for each LCD board that you would like to use.

Figure 10. Adding rows

Step 3. Double click on the element added.

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AEK_LCD_DT028V1 component

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