The PC Remote Display is connected serially to a PC. A small tool on the PC is periodically taking screenshots of parts of the desktop and sending these to the Remote Display which is displaying it.

1.2 Hardware Parts

eZ80F91 Acclaim! Contest Kit
Graphic LCD Module; COG 128X64C1

1.3 Software Parts

Firmware for the Microcontroller
PC Application for taking the screenshots

2. Hardware

2.1 LCD Connections

The Display is connected by a 8-Bit databus and 4 control lines. It is attached to the contest kit like shown on the table below.

LCD Display	Microcontroller	Signal
D0	PA0	Databit 0
D1	PA1	Databit 1
D2	PA2	Databit 2
D3	PA3	Databit 3
D4	PA4	Databit 4
D5	PA5	Databit 5
D6	PA6	Databit 6
D7	PA7	Databit 7
RS	PC0	Register Select
RW	PC1	Read/Write
E	PC2	Enable (Clock)
Reset	PC3	Reset

2.2 LCD Electronics

The display only needs some capacitors to generate the desired voltages to drive the LCD. All other parts are integrated in the chip on glass.

2.3 LCD Description

Type: Tecdis COG 128X64C1

Heart of the display is a Samsung ICS6B0724 driver IC.

The display has a resolutiuon of 128x64 Pixels and an integrated green LED-Backlight.

It has 1kB RAM to hold the whole screen area, which can be written and read.

The memory is organized in this way:

The displayed area is divided into 8 lines or pages. Each page is divided into 128 columns of 8 Bits.

Its possible to read/write the columns in a random order.

3. Firmware

For softwaredevoloping, the delivered tool ZDS II eZ80Acclaim! was used.

I used the StarterProject in the Samples-Directory as a basis for my project.

After the building process in release mode, the image can be flashed into the eZ80.

3.1 Requirements

Serial Interface (fast, 115200Baud)
Timer
LCD Driver

3.2 Interrupt setup

To use the timer and serial interface in a nice way, its necessary to fire events if a defined time has elapsed or a character was received.

Firstly we need the vector addresses of the desired interrupt sources from the hardware manual and define it in the code.

#define VECTOR_UART0 0x70

#define VECTOR_TIMER0 0x54

Then we need these forward declarations.

extern void init_default_vectors(void);

extern void set_vector(unsigned short vector,void (*hndlr)(void));

After the registers of the timer and uart are properly set up, we can assign the IRQ-Functions to the vectors.

set_vector(VECTOR_UART0, UART_Receive);

set_vector(VECTOR_TIMER0, TIMER0_IRQ);

Last but not least, the irqs can be activated.

UART0_IER = UART0_IER | B0;

TMR0_IER = TMR0_IER | B0;

3.3 Timer Interrupt

The timer is initialized to fire every 10ms.

void timer_init(void)

{

TMR0_CTL = TMR0_CTL | B4; // Clock Divide: 256

TMR0_CTL = TMR0_CTL | B3; // Clock Divide: 256

TMR0_CTL = TMR0_CTL | B2; // Continous mode

TMR0_CTL = TMR0_CTL | B1; // Force Auto Reload

TMR0_RR_L = 161; // Timerinterrupt every 10ms; (50MHz/256)/1953

TMR0_RR_H = 7; // Timerinterrupt every 10ms; (50MHz/256)/1953

TMR0_CTL = TMR0_CTL | B0; // Start Timer

}

Here is the timer-interrupt itself

void interrupt TIMER0_IRQ(void)

{

char dummy;

dummy = TMR0_IIR; // Dummy read to clear irq-flag

if (SerialTimeout < 2000)

{

SerialTimeout++;

}

// If no byte was received for 30ms, reset bytecounter

if (SerialTimeout > 2)

{

count = 0;

}

Firstly the IIR-Register must be read to clear the interrupt flag.

Now it is checked if the SerialTimeout-Counter is already on the max. If not, it is incremented.

If the SerialTimeout is over 2 counts (3 counts = 30ms), we are in the timeout condition and the bytecounter for the display data is reset. This occurs if a person unplugs the serial cable while a picture is receiving.

Then the timeout resets the bytecounter count and after plugging the cable, the next picture can be received perfectly.

The SerialTimeout is reset by an uart-interrupt if a character was received.

3.4 UART Interrupt

In the UART Interrupt the data for the display is received.

void interrupt UART_Receive(void)

{

char character;

character = UART_RBR; // Read received character

SerialTimeout = 0; // Character was received; reset Timeout-Counter

PictureBuffer[count] = ~character; // Put inverted byte in Picturebuffer

// If picture is complete, set flag for main loop to display it

count++;

if (count >= sizeof(PictureBuffer))

{

count = 0;

NewPicture = 1;

}

If the interrupt has fired, the received character can be copied from the RBR register into the PictureBuffer. The bytecounter-variable count is incremented by 1 so the next received character is stored in the right position in the PictureBuffer.

The SerialTimeout-variable is reset each time a character is received.

If count has the same value as the length of the PictureBuffer (8 Pages * 128 Columns = 1024), the picture is complete.

A flag (NewPicture) is set to tell the main loop that a new picture is available.

3.5 LCD Driver

The LCD Driver is located in two separate files called glcd.h and glcd.c. It has functions to startup/init the display GLCD_Init() and functions to set/reset pixels, write text, draw lines/circles/boxes

For this project, the function GLCD_WriteDisplayByte() is the most used.

void GLCD_WriteDisplayByte(unsigned char page, unsigned char line, unsigned char databyte)

{

GLCD_SetPage(PE1, page);

GLCD_SetYAddress(PE1, line);

GLCD_WriteDisplayData(PE1, databyte);

}

We set the cursor (memory pointer) to the desired page and column and then write the new databyte to this location.

The parameter PE1 is the bitposition, where the enable-signal is connected to the microcontroller. This is useful if displays with two display-controllers are connected.

In this configuration it is always PE1.

All instructions of the display are listed on page 35 of the Samsung S6B0724 datasheet.

3.6 Main program

After startup, some initializations are made to set up the timer, uart and show a startpicture on the LCD.

Now we enter the while(1) loop until powerdown

while (1)

{

// If new picture was received

if (NewPicture)

{

index = 0; // Reset Byteindex

for (page=0; page<8; page++)

{

for (line=0; line <128; line++)

{

GLCD_WriteDisplayByte(page, line, PictureBuffer[index]);

index++;

}

NewPicture = 0;

}

// If no picture was received for 10 seconds, show standard picture

if (SerialTimeout > 1000)

{

GLCD_ShowPicture(0);

}

If a new picture is available (NewPicture != 0), the array PictureBuffer can be sent byte by byte to the display.

After that, the flag NewPicture is reset.

If for more than 10 seconds no data was received, a standard pictured will be showed.

4. PC Software

The PC Software is written in Microsoft Visual Studio .NET with the programming language C#.

Its required to have installed the freely available .NET framework from Microsoft to run the .exe.

4.1 Requirements

Serial Interface (fast, 115200Baud)
Screenshot function

4.4 Settings Window

5. PC Remote Display in action

5.1 Photos

PC Monitor	PC Remote Display