CODEWITHSUNDEEP
serial-portmicrocontroller8051microprocessors
Omar Nasir
Omar Nasir

Reputation: 1

Asynchronous UART transfer in microcontroller 8051

Hi i am trying to communicate my 89c52 with sim548c module. I am sending AT commands and then making the microcontroller store all replies in an array and go through a search function to see if proper reply was sent so it can move on to next AT command. This requires two way serial transfer. i have to first send serially the AT command, then enable reception and store all replies from the module in an array. I am using this program but i cant get the microcontroller to accept the incoming data and store it in an array. it transfers successfully but doesnt receive. Can you kindly identify what is the problem?

int check=0;
int out=0;
unsigned char info[20]={"00000000000000000000"};
unsigned char  *s;
unsigned char a[3],b[3];

void transmit_data(unsigned char str)        
{
    SBUF=str;                                  
    while(TI==0);
    TI=0;                          
}

void send_serial(unsigned char *s)
{
    delay(50);
    while(*s!=0x0)
    {
        SBUF=*s;
        while(TI==0)
        {
        }
    TI=0;
    s++;
    }
}

void receive_data()            interrupt 4                      
{
    if(RI)
    {
        info[check++]=SBUF;
        RI=0;
    }
    if(TI)
        TI=0;
}

void search(unsigned char b[])
{
    int l=0;
    for(l;l<18;l++)
    {
        if(info[l]==b[0] && info[l+1]==b[1] && info[l+2]==b[2])
        {
            out=1;
            break;
        }
    }
}

void compare(unsigned char *s, unsigned char a[]) //for CIPSEND
{
    while(1)
    {
        out=0;
        check=0;
        delay(50);
        send_serial("AT+CIPSEND\r");
        delay(100);
        send_serial(s);
        transmit_data(0x0D);
        transmit_data(0x0A);
        transmit_data(0x1A);
        IE=0x90;
        delay(200);
        IE=0x88;
        search(a);  
        if (out==1)
        break;
    }
}

Upvotes: 0

Views: 2039

Answers (2)

tommy
tommy

Reputation: 11

i have seen this a couple of times and th mistake is that your serial receive works with an interrupt and it is not a voidable function smply remove the VOID that is attached to INTERRUPT 4 so tha ur code becomes 

 receive_data()            interrupt 4                      
{
    if(RI)
    {
        info[check++]=SBUF;
        RI=0;
    }
    if(TI)
        TI=0;
}

Upvotes: 1

XTL
XTL

Reputation: 851

I would suggest making a smaller (as simple as you can) program that does nothing more than receive (by interrupt?) data and blink a LED or echo it back or in some other way indicate that you can reliably receive. Use that to talk to a terminal emulator or another known working interface. Cut out all possible middlemen and unknowns.

Check also UART error registers and configuration to make sure your clock/parity/data settings match in both ends. Start with a slow rate first.

Make one piece at a time work reliably, then put them together.

Upvotes: 0

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