Cortex_A9----UART

一、看原理图
    找到UART对应的引脚
    GPA1_0
    GPA1_1

    配置功能
    GPA1CON
    GPA1CON[1] [7:4]：0x2 = UART_2_TXD
    GPA1CON[0] [3:0]：0x2 = UART_2_RXD
    禁止上下拉
    GPA1PUD

二、串口的传输协议
    1个start位   起始位
    5-8个数据位
    0或者1个奇偶校验位
    1或者两个停止位
    我们常用的： 1个起始位，8个数据位，没有奇偶校验位，1个停止位   8N1

    ULCON2
    0x3     8N1
    UCON2
    Transmit Mode [3:2]: 01 = Interrupt request or polling mode   //我们用的是轮询（polling）
    Receive Mode  [1:0]: 01 = Interrupt request or polling mode


    UTRSTAT2
    Transmitter empty [2] : 0 = Not empty
                                      1 = Transmitter empty
    Transmit buffer empty [1]: 0 = Buffer is not empty
                                           1 = Buffer is empty 
    Receive buffer data ready [0] : 0 = Buffer is empty
                                                1 = Buffer has a received data
 
    UTXHn
    UTXHn  [7:0]  RWX  Transmits data for UARTn  
    URXHn
    URXHn  [7:0]  R  Receives data for UARTn 

    UBRDIVn                  53
    UBRDIVn  [15:0]  RW  Baud-rate division value 
    UFRACVALn                5
    UFRACVALn  [3:0]  RW  Determines the fractional part of Baud-rate divisor. 

    DIV_VAL = UBRDIVn + UFRACVALn/16
    or
    DIV_VAL = (SCLK_UART/(bps * 16)) - 1

    DIV_VAL = (40000000/(115200 *  16)) – 1
    = 21.7 – 1
    = 20.7
    UBRDIVn = 20 (integer part of DIV_VAL)    (取整)
    UFRACVALn/16 = 0.7
    Therefore, UFRACVALn = 11                 （四舍五入）

    DIV_VAL = (100000000/(115200 *  16)) – 1
    = 54.3 – 1
    = 53.3
    UBRDIVn = 53 (integer part of DIV_VAL)
    UFRACVALn/16 = 0.3   UFRACVALn  = 16*0.3 =4.8 ==>  5

#include "exynos_4412.h"
#include "adc.h"


void delay_ms(unsigned int Time)
{
        unsigned int i,j;
        for(i=0;i for(j=0;j<3000;j++);
}

/* UART初始化 */
void myuart_init()
{
        /* 设置GPA1_0和GPA1_1引脚为uart的输入和输出功能 */
        GPA1.CON = GPA1.CON & (~(0xFF << 0)) | (0x22 << 0);
        /* 设置GPA1_0和GPA1_1引脚禁止上下拉 */
        GPA1.PUD = GPA1.PUD & (~(0xF << 0));
        / * 设置UART传输模式：8N1 */
        UART2.ULCON2 = UART2.ULCON2 & (~(0x3 << 0)) | (0x3 << 0);
        UART2.UCON2 = UART2.UCON2 & (~(0x5 << 0)) | (0x5 << 0);


        /*
        * 设置波特率
        * Baud-rate 115200: src_clock:100Mhz
        * DIV_VAL = (100*10^6 / (115200*16) -1) = (54.3 - 1) = 53.3
        * UBRDIV2 = (Integer part of 53.3) = 53 = 0x35
        * UFRACVAL2 = 0.3*16 = 0x5
        * */
        UART2.UBRDIV2 = 53;
        UART2.UFRACVAL2 = 5;
        return ;
}


/* UART发送数据 */
void transmit_char(unsigned char data)
{
        /* 等待发送缓冲区为空再将数据放入发送缓冲区中 */
        while(!(UART2.UTRSTAT2 & (0x1 << 1)));
        UART2.UTXH2 = data;
        return ;
}


/* UART接收数据 */
unsigned char receive_char()
{
        unsigned temp_data;
        while(!(UART2.UTRSTAT2 & (0x1 << 0)));
        temp_data = UART2.URXH2;
        return temp_data;
}

int main()
{
        /* UART初始化 */
        myuart_init;
        delay_ms(500);
        /* ADC初始化 */
        adc_init();
        delay_ms(500);
        while(1)
        {
                transmit_char(adc_Converter_Value());
                printf("adc value: %x \n", adc_Converter_Value());
                delay_ms(2000);
        }

        return 0;
}