/*****************************************************************
//ICC-AVR application builder : 2005-8-19 14:40:53
// Target : M8
// Crystal: 7.3728Mhz
// Crystal: 4.6080Mhz

實(shí)驗(yàn):做usart串行通訊實(shí)驗(yàn)
目的:了解及會(huì)使用usart串口
CPU:atmega8L
相關(guān)的5個(gè)寄存器:UCSRA,UCSRB,UCSRC,UDR,UBRR(UBRRH,UBRRL)
	         其中:UBRRH和UCSRC共用一個(gè)地址
******************************************************************/
/*配置:CKOPT=0,CKSEL3..0=1111,SUT1..0=11(65ms慢速上升電源)*/
#include <iom8v.h>
#include <macros.h>

#define  Fosc_4608  // 選擇4.608M晶振crystal
#define  true    1
#define  false   0

#ifdef  Fosc_73728
#define baudrate   47   //波特率為9600b/s
//#define baudrate  191    //波特率為2400b/s
#endif

#ifdef  Fosc_4608
//#define baudrate  29 //波特率為9600b/s
#define baudrate  119 //波特率為2400b/s
#endif

/* UART Buffer Defines */
#define UART_RX_BUFFER_SIZE 32 
#define UART_TX_BUFFER_SIZE 32 
unsigned char UART_RX_buff[UART_RX_BUFFER_SIZE];
unsigned char UART_TX_buff[UART_TX_BUFFER_SIZE];

unsigned char Temp;
unsigned char Tx_Flag,Rx_Flag;
unsigned char Error_Flag;


void main(void)
{
	init_devices();
	init_data();
  
	while(1)  //forever
	   {
	     if(Rx_Flag == true)
	     	 {
	     	 	 UDR = Temp;//start send
				 Temp = 0;
	     	 	 //Rx_Flag = false;  //標(biāo)志位在發(fā)送成功后,再清零
	     	 	 
	     	 }
	     if(Error_Flag == true)
	     	{
	     		if(Temp == 0x00)
	     			Rx_Flag = false;
	     		else
	     			Rx_Flag = true;
	     	}
	   }
}

void init_data(void)
{
  Temp = 0x33;
  Tx_Flag    = false;
  Rx_Flag    = false;
  Error_Flag = false;
}

#pragma interrupt_handler uart0_rx_isr:12
void uart0_rx_isr(void)
{
 //uart has received a character in UDR
 Temp = UDR;
 Rx_Flag = true;
}

#pragma interrupt_handler uart0_udre_isr:13
void uart0_udre_isr(void)
{
 //character transferred to shift register so UDR is now empty
 //UDR = temp;//have sent and reload 發(fā)送完,and重裝
 Error_Flag = true;
}

#pragma interrupt_handler uart0_tx_isr:14
void uart0_tx_isr(void)
{
 //character has been transmitted
 Rx_Flag = false;//說明已發(fā)送成功 send successfully
}


void port_init(void)
{
 PORTB = 0x00;
 DDRB  = 0x00;
 PORTC = 0x00; //m103 output only
 DDRC  = 0x00;
 PORTD = 0x00;
 DDRD  = 0x00;
}
//UART0 initialize
// desired baud rate: 9600
// actual: baud rate:9600 (0.0%)
// char size: 8 bit
// parity: Disabled
void uart0_init(void)
{
  
 UCSRB = 0x00; //disable while setting baud rate
 //UCSRB[RXCIE,TXCIE,UDRIE,RXEN,TXEN,UCSZ2,RXB8,TXB8]
 //Bit 7 – RXCIE: RX Complete Interrupt Enable

 UCSRA = 0x00;
 //UCSRA[RXC,TXC,UDRE,FE,DOR,PE,U2X,MPCM]
 
 UCSRC = (BIT(URSEL)|BIT(UCSZ1)|BIT(UCSZ0));//設(shè)置成8位
 //UCSRC[URSEL,UMSEL,UPM1,UPM0,USBS,UCSZ1,UCSZ0,UCPOL]
 //位URSEL:寄存器選擇("1"為UCSRC或"0"為UBRRH)
 //位UMSEL:工作模式選擇(0為異步,1為同步)
 //位UPM1..0:為校驗(yàn)方式,硬件支持校驗(yàn)
 //位USBS:停止位選擇(0為一位,1為兩位)
 //位UCSZ0..2:發(fā)送位數(shù)選擇(如果是8位:011)
 //位UCPOL:時(shí)鐘極性(只在同步模式使用,異步應(yīng)置為"0")
 
 //UBRRL = 0x2F; //set baud rate lo
 //UBRRH = 0x00; //set baud rate hi(設(shè)置波特率只用低四位,加起來一共12位)
 UBRR = baudrate; /* set the baud rate */
 
 UCSRB = ((1<<RXCIE)|(1<<TXCIE)|(1<<RXEN)|(1<<TXEN));
}

void twi_init(void)
{
 	TWCR = 0x00;
	TWBR = 0x20;
	TWSR = 0x00;
	TWAR = 0x00;
	TWCR = ((1<<TWEA)|(1<<TWEN));//TWINT???
	//TWCR[TWINT,TWEA,TWSTA,TWSTO,TWWC,TWEN,-,TWIE]
}

//call this routine to initialize all peripherals
void init_devices(void)
{
 //stop errant interrupts until set up
 CLI(); //disable all interrupts
 port_init();
 uart0_init();
 twi_init();

 MCUCR = 0x00;
 GICR  = 0x00;
 TIMSK = 0x00; //timer interrupt sources
 SEI(); //re-enable interrupts
 //all peripherals are now initialized
}