从SIM808接收数据

Question

我正在尝试使用SIM808模块，但是即使仅发送" AT"也没有响应。我使用的是5V/2.5A AC/DC适配器。董事会（ECB-V3.2）的连接良好，因为两个二极管一直在上面，一个二极管每三秒钟闪烁一次。我通过将UART代码从UC到PC发送并接收数据来尝试使用我的UART代码。我还尝试在代码的不同部分显示一些数据，以找到带有错误的行。我认为这个问题是在我正在等待接收SIM808模块的单个字符的同时循环中。我在代码中标记了这一行（在函数 uart_rxchar（））中。我使用的是我的代码中的两个UART，一个用于在UC和PC之间发送数据（代码中的频道0），第二个用于在UC和SIM808（频道1）之间发送数据，但我在计算机上检查了两个版本。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("rnstart", 0);
    while(1)
    {
        char ans[15] = "";
        DDRE = 0xff;
        UART_TxString("ATrn",1);
        DDRE = 0x00;
        UART_RxString(ans,1);
        _delay_ms(2000);
    }
}

我还检查了发送的所有可能性：ATr", "ATn", "ATrn", "ATnr。

预先感谢您的任何帮助。

Answer 1

问题是您正在将接收到的字符回到LINE上的SIM808模块

上

UART_TXCHAR（CH，频道）;//回声回到收到的char

这可能会使SIM808混淆并将其放在不一致的状态下。

尝试将SIM808模块连接到PC，并使用Coolterm在命令触发后分析响应。