Embedded system development and labs for ARM (R. Muresan, 2005)

Embedded Systems Development and Labs; The English Edition

(3) ADC Data Register (ADCDAT)

2) A/D Conversion Time

When the system clock frequency is 66MHz and the prescaler value is 20 the total 10-bit conversion time is the following:

66 MHz / 2(20+1) / 16(at least 16 cycle by 10-bit operation) = 98.2 KHz = 10.2 us

NOTE: Because this A/D converter has no sample-and-hold circuit, the analog input frequency should not exceed 100Hz for accurate conversion although the maximum conversion rate is 100KSPS.

3) Programming the ADC

●The ADC conversion error is decreased if the ADCPSR is large in comparison to the above ADC conversion time. If you want accurate ADC conversion, the ADCPSR should be as large as possible.

●Because our ADC has no sample & hold circuit, the input frequency bandwidth is small 0~100Hz.

●If the ADC channel is changed, a channel setup time (min. 15us) is needed.

●After the ADC exits the sleep mode (the initial state is the sleep mode), there is a 10ms wait needed for the ADC reference voltage stabilization, before the first AD conversion can take place.

●Our ADC has ADC start-by-read feature. This feature can be used for DMA to move the ADC data to memory.

5.3.5 Lab Design

1. Touch Panel Circuit Design

The touch panel circuit is shown in Figure 5-25. When the touch panel is pressed, the CPU will receive an interrupt signal. The interrupt service routine will process the Q1, Q2, Q3, Q4 and the A/D conversion.

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Figure 5-25 Touch Panel Circuit

2. Software Design

The touch screen related software includes the serial port data transfer program, the LCD display program, the touch screen calibration and interrupt service routine, and other auxiliary programs. For the serial port data transfer program, please refer to the “Serial Port Communication Lab”. For the LCD display program, please refer to the “LCD Display and Control Lab”. The touch screen calibration of this Lab uses two dots diagonal calibration. The flow diagram of touch screen control program is shown in Figure 5-26.

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Figure 5-26 Touch Screen Software Flow Diagram

5.3.6 Operational Steps

1)Prepare the Lab environment. Connect the Embest Emulator to the target board. Connect the target board UART0 to the PC serial port with the serial cable provided by the Embest development system.

2)Run the PC Hyper Terminal (set to 115200 bits per second, 8 data bits, none parity, 1 stop bits, none flow control).

3)Connect the Embest Emulator to the target board. Open the TouchScreen_test.ews project file found in the TouchScreen sub directory of the Examples directory. After compiling and linking, connect to the target board and download the program.

(4) Watch the main window of the hyper terminal; the following information should be displayed: Pixel: 320 X 240. Coordinate range designing…

Touch screen coordinate range in: (Xmix, Ymin) is: (0200,0120) (Xmax,Ymax) is: (0750,0620)

To use current settings. Press N/n key.

Want to set again (Y/N)?

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The information gives the current valid coordinate range. These are factory default values. The user can select Y/y to calibrate the TSP again. Otherwise use the default value.

When ‘calibrating the TSP’ is selected, any two points of the diagonal should be pressed using a finger or a small stick. The hyper terminal will show the coordinate values that the user inputted and will decide if they are valid. The touch screen program will output the new coordinate values. The user can accept them or calibrate the screen coordinates again.

The hyper terminal will show the following:

Touch TSP’s corner to ensure Xmax, Ymax, Xmin, Ymin

User touch coordinate (X,Y) is: (0510,0479)

User touch coordinate (X,Y) is: (0364,0382)

Touch screen coordinate range in: (Xmix, Ymin) is: (0200,0120) (Xmax,Ymax) is: (0750,0620)

To use current settings, press N/n key.

Want to use again? (Y/N)

After the coordinates are calibrated, the user can press on the touch panel in the valid range. The hyper terminal will output the coordinate values:

Want to Set Agin? (Y/N)? n

Pixel: 320 X 240. Coordinate Range in: (0,0)-(320,240)

LCD TouchScreen Test Example (please touch LCD screen)

(5) After understanding and mastering the lab, finish the Lab exercises.

5.3.7 Sample Programs

Because the LCD and serial pot are used, the initialization code should include LCD initialization and serial port initialization. The initialization of A/D converter could be done at run time.

1) Environment Variable Initialization

Port_Init();

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Embedded Systems Development and Labs; The English Edition

RIISPC = 0xffffffff;

Uart_Init()(0,115200);

char oneTouch; unsigned int Vx; unsigned int Vy; unsigned int Xmax; unsigned int Ymax; unsigned int Xmin; unsigned int Ymin;

TSPX(GPE4_Q4(+)) TSPY(GPE5_Q3(-)) TSMY(GPE6_Q2(+)) TSMX(GPE7_Q1(-))

rINTMSK =~(BIT_GLOBAL|BIT_EINT2);

2) LCD Initialization (please refer to 5.1 “LCD Display Lab”)

/*********************************************************************

*modify:

*comment:

**********************************************************************/

void Lcd_Init(void)

{

rDITHMODE=0x1223a; rDP1_2 =0x5a5a; rDP4_7 =0x366cd9b; rDP3_5 =0xda5a7; rDP2_3 =0xad7; rDP5_7 =0xfeda5b7; rDP3_4 =0xebd7;

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rDP4_5 =0xebfd7; rDP6_7 =0x7efdfbf;

rLCDCON1=(0)|(1<<5)|(MVAL_USED<<7)|(0x0<<8)|(0x0<<10)|(CLKVAL_GREY16<<12); rLCDCON2=(LINEVAL)|(HOZVAL<<10)|(10<<21);

rLCDSADDR1= (0x2<<27) | ( ((LCD_ACTIVE_BUFFER>>22)<<21 ) | M5D(LCD_ACTIVE_BUFFER>>1));

rLCDSADDR2= M5D(((LCD_ACTIVE_BUFFER+(SCR_XSIZE*LCD_YSIZE/2))>>1)) | (MVAL<<21);

rLCDSADDR3= (LCD_XSIZE/4) | ( ((SCR_XSIZE-LCD_XSIZE)/4)<<9 ); // enable,4B_SNGL_SCAN,WDLY=8clk,WLH=8clk,

rLCDCON1=(1)|(1<<5)|(MVAL_USED<<7)|(0x3<<8)|(0x3<<10)|(CLKVAL_GREY16<<12); rBLUELUT=0xfa40;

//Enable LCD Logic and EL back-light. rPDATE=rPDATE&0xae;

}

2. Coordinate Range Value Calibration

/************************************************************************

*modify:

*comment:

***********************************************************************/

void DesignREC(ULONG tx, ULONG ty)

{

int tm;

Uart_Printf("\n\r User touch coordinate(X,Y) is :"); Uart_Printf("(%04d",tx);

tm = tx; tx = Vx; Vx = tm; // tx as Xmin

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}

if(Vy < ty )

{

tm = ty; ty = Vy; Vy = tm; // ty as Ymin

CheckTSP = 0;// has checked }// end if(oneTouch == 0)

}

3. Interrupt Service Routine

/***********************************************************************

*modify:

*comment:

*********************************************************************/

void TSInt(void)

{

int i; char fail = 0;

ULONG tmp; ULONG Pt[6];

//<X-Position Read>

//TSPX(GPE4_Q4(+)) TSPY(GPE5_Q3(-)) TSMY(GPE6_Q2(+)) TSMX(GPE7_Q1(-))

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}

// read X-position average value

Pt[5] = (Pt[0]+Pt[1]+Pt[2]+Pt[3]+Pt[4])/5;

tmp = Pt[5];

//<Y-Position Read>

//TSPX(GPE4_Q4(-)) TSPY(GPE5_Q3(+)) TSMY(GPE6_Q2(-)) TSMX(GPE7_Q1(+))

if(!(CheckTSP|(tmp < Xmin)|(tmp > Xmax)|(Pt[5] < Ymin)|(Pt[5] > Ymax))) // Is valid value?

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}

5.3.8 Exercises

Refer to the LCD Display Lab and write a program that accepts 4 points pressed on the touch panel and display the rectangle using the 4 coordinate values.

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Chapter 6 Communication and Voice Interface Labs

6.1 IIC Serial Communication Lab

6.1.1 Purpose

●Understand the usage of IIC serial communication protocol.

●Learn the method of writing/reading the EPROM component of the board.

●Learn the usage of the S3C44BoX Micro IIC controller via the Lab.

6.1.2 Lab Equipment

● Hardware: Embest S3CEV40 hardware platform, Embest Standard/Power Emulator, PC. ● Software: Embest IDE 2003, Windows 98/2000/NT/XP operation system.

6.1.3 Content of the Lab

Write a program that can read and write the AT24C04 EPROM component on the development board. Implement a program that can write data to an address, read it from the same address and compare the results. Test the functionality of the EPROM AT24C04 and the microprocessor IIC interface.

6.1.4 Principles of the Lab

1. IIC Interface and EEPROM

IIC bus is a serial synchronized data transfer bus. Its standard data transfer rate is 100kb/s. The enhanced bus data transfer rate is 400kb/s. The IIC bus control can be organized as multi-master system or master-slave system. In multi-master system, the system gets the bus control via hardware arbitration or software arbitration. In applications, master-slave system is most often used. The master-slave system has only one main control point while other devices on the bus are all slaves. The addresses of the devices on the IIC bus are determined by the address bus interconnection. The lowest bit of the address determines the direction of read and write.

Currently most of the memory chips are EEPROM and their most often-used communication protocols are two wires serial interconnection protocol (IIC) and three wires serial interconnection protocol.

There are many models of IIC EPROM. The AT24CXX series are common used model. The AT24CXX series include AT2401/02/04/08/16, etc. They support 2-5V low voltage operation and their bit capability (bits/page) is 128x8 / 256x8 / 512x8 / 1024 x8/ 2048x8.

AT24Series chips are manufactured using the CMOS technology. With an internal high voltage charge pump, AT24Series chips can work from a single power supply. The standard package is 8-pin DIP package as shown in Figure 6-1.

Figure 6-1 Standard Package Pins

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