测试程序五 UART通讯协议

该"测试程序"系列的编写是为了检测学校实验室板子上的各个部分是否正常工作 同时复习之前实验的知识要点 由于代码上附带多数注释 故此文只放代码 不再多做注解

/*
  作者：Murrey_Xiao
  编写时间：2017.6.5
  
  功能介绍：
  该程序为MEGA16上UART的测试代码。
  UART通讯主要控制通讯双方的波特率和帧格式，与时钟频率无关。

  USART_sendData8()实现数据的发送
  USART_getData8()或uart0_rx_isr()中断实现数据的接收
  使用中断实现数据接收时，
  需要初始化寄存器B：UCSRB |= (1<<RXCIE);并编写中断服务程序。

  注意：设置帧格式时：UCSRC |= (1<<URSEL)|(1<<USBS)|(3<<UCSZ0); 
  即必须在使能URSEL的同时，对其他项同时进行设置，否则设置无效。
*/
#include <iom16v.h>
#include <macros.h>

#define MCLK 7.3728

void port_init(void)
{
    PORTA = 0x00;
    DDRA  = 0xff;
}
unsigned char USART_getData8(void)
{
    // wait for receiving the data completed
    while (!(UCSRA & (1<<RXC))) ;
    // return the data
    return UDR;
}
void USART_sendData8(unsigned char data)
{
    // wait for UDR empty
    while (!(UCSRA & (1<<UDRE))) ;
    // assign the data to UDR, ready to send
    UDR = data;
}
/*
#pragma interrupt_handler uart0_rx_isr:iv_USART0_RXC
void uart0_rx_isr(void)
{
    //uart has received a character in UDR
    dataGet=UDR;
}
*/
void USART_init(unsigned int baud) 
{
    unsigned int ubrr_calc;
    
    //UCSR Init
    UCSRA = 0x00;
    UCSRB = 0x00;
    UCSRC = 0x00;
    
    // set baud rate
    UCSRC &=~(1<<URSEL);    //EN UBRRH
    ubrr_calc=MCLK*1000000/16/baud-1;
    UBRRL = (unsigned char)ubrr_calc;
    UBRRH = (unsigned char)(ubrr_calc >> 8);
    
    // enable TX and RX
    UCSRB |= (1<<RXEN) | (1<<TXEN); 

    // enable complete action to interrupt
    //UCSRB |= (1<<RXCIE);
    
    // set frame format
    // EN UCSRC / 2 bit for stop / 8 bit for data / no check
    UCSRC |= (1<<URSEL)|(1<<USBS)|(3<<UCSZ0);    
}

//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();
    USART_init(9600);

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


int main(void)
{
    unsigned char i;
    init_devices();
    while(1)
    {
        PORTA = USART_getData8();
    }
    return 0;
}