Question

我正在尝试使用SIM808模块，但是即使仅发送“ AT”也没有响应。我正在使用5V / 2.5A AC / DC适配器。电路板（ecb-v3.2）的连接良好，因为两个二极管一直处于打开状态，一个二极管每三秒钟闪烁一次。我通过从uC向PC发送和接收数据尝试了我的UART代码，它起作用了。我还尝试在代码的不同部分显示一些数据，以查找包含错误的行。我认为问题出在while循环中，我正在等待从SIM808模块接收单个字符。我在代码中标记了这一行（在函数 UART_RxChar（）中）。我在代码中使用了两个UART，一个用于在uC和PC之间发送数据（代码中的通道0），另一个用于在uC和SIM808之间发送数据（通道1），但是我在计算机上检查了这两个版本。这是我的代码：

#define F_OSC 7372800UL
#define BAUD 115200
#define ubrr ((F_OSC/16/BAUD)-1)
#include <avr/io.h>
#include <util/delay.h>
#include "lcd.h"

void UART_TxString(char *string_ptr, uint8_t channel);

void UART_Init( uint8_t channel )
{
    if ( channel == 0)
    {
        /*Set baud rate */
        UBRR0H = (unsigned char)(ubrr>>8);
        UBRR0L = (unsigned char)ubrr;
        /*Enable receiver and transmitter */
        UCSR0B = (1<<TXEN0) | (1<<RXEN0);
        /* Set frame format: 8data, 1stop bit */
        UCSR0C = (1<<UCSZ00) | (1<<UCSZ01);
    }
    else
    {
        /*Set baud rate */
        UBRR1H = (unsigned char)(ubrr>>8);
        UBRR1L = (unsigned char)ubrr;
        /*Enable receiver and transmitter */
        UCSR1B = (1<<TXEN1) | (1<<RXEN1);
        /* Set frame format: 8data, 1stop bit */
        UCSR1C = (1<<UCSZ10)|(1<<UCSZ11);
    }
}

char UART_RxChar( uint8_t channel )
{

    if ( channel == 0 )
    {
        while((UCSR0A & (1<<RXC0))==0);   // Wait till the data is received
        return(UDR0);                    // return the received char
    }
    else
    {
        //Here is the problem. The condition in the loop is always true.
        while((UCSR1A & (1<<RXC1))==0);   // Wait till the data is received
        return(UDR1);                    // return the received char
    }

}
void UART_TxChar(char ch, uint8_t channel)
{
    if ( channel == 0)
    {
        while((UCSR0A & (1<<UDRE0))==0); // Wait till Transmitter(UDR) register becomes Empty
        UDR0 =ch;             // Load the data to be transmitted
    }

    else
    {
        while((UCSR1A & (1<<UDRE1))==0); // Wait till Transmitter(UDR) register becomes Empty
        UDR1 =ch;             // Load the data to be transmitted
        UART_TxChar(ch,0);
    }

}
void UART_TxString(char *string_ptr, uint8_t channel)
{
    while(*string_ptr)
    UART_TxChar(*string_ptr++, channel);
}
void UART_RxString(char *string_ptr, uint8_t channel)
{
    char ch;
    while(1)
    {
        ch=UART_RxChar(channel);    //Reaceive a char
        UART_TxChar(ch, channel);     //Echo back the received char
        if((ch=='\r') || (ch=='\n')) //read till enter key is pressed
        {                          //once enter key is pressed
            *string_ptr=0;          //null terminate the string
            break;                //and break the loop
        }
        *string_ptr=ch;              //copy the char into string.
        string_ptr++;                //and increment the pointer
    }
}

int main(void)
{
    UART_Init(0);
    UART_Init(1);
    initLCD();
    UART_TxString("\r\nstart", 0);

    while(1)
    {
        char ans[15] = "";
        DDRE = 0xff;
        UART_TxString("AT\r\n",1);
        DDRE = 0x00;
        UART_RxString(ans,1);
        _delay_ms(2000);
    }
}

我还检查了所有发送可能性：AT\r", "AT\n", "AT\r\n", "AT\n\r。

在此先感谢您的帮助。

Answer 1

问题是您正在将收到的字符回传到线路上的SIM808模块

UART_TxChar（ch，通道）; //回显收到的字符

这可能会使SIM808混乱并使其处于不一致状态。

尝试将SIM808模块连接到PC，并在触发AT命令后使用CoolTerm分析响应。

从SIM808接收数据

1 个答案: