8051 keeps executing

Hi Sandeep,

It happens just because of the absence of while(1) loop in your code.

Once your code done all the steps it simply won’t stop anmd remain idle, rather it redo executing from the first step. To avoid such situation people use while(1) or infinite loop at the end of their code. It helps in such a way that once the entire code is finished executing the controller enters into the infinite loop and remains there idle.

Just add

while(1);

at the end of your code and i hope it will solve the proble.

Also connect the Rx pin of the MCU to the Tx pin of the SIM300 only when it is necessary.

Thanks a lot for the suggestion . Now its executing only once . But if in case i have to send a data , i use a function

send_data(args);

while(1);

now my intention is to wait for another data to come from the other end . and now that there is a while(1); do you think it is possible.

I send AT only once

I have to wait for OK

in the waiting period how do stop my 8051 from re-executing

I hope u understood my problem 

and thanks a lot in advance

Hi Sandeep,

Nice question.

You can use the while loop itself to wait till something happens.

For example you want to turn on an LED after the voltage at a pin say ‘P’ goes high. It can be done like the following;

//

while ( P = = 0 );       // the code will continue looping here until the condition fails,  

                                  // means when the pin value becomes 1

led_on ();

//

Hope you got the idea.

Thanks  alot for the reply

I am stuck up in dis problem pls help me out with dis

the problem is :

TO SIM900:

PC-> Hyperterminal -> ATD9738XXXX18;<enter>  : i get a call

8051 -> same command : not getting a call

have sent a carriage return after the command (0x0D)

used realterm to check if the data coming out of 8051 is right . it is perfect when i compared wat i manually send and the command coming out of the 8051.

SIM900 sends OK to the hyperterminal after the command 

but it exactly sends <CR><LF>OK<CR><LF>

i didnt write a routine to recieve data in 8051. will that be a problem?

Next i did write a code to recieve and parallely as i recieve data i have to display it on the LCD(16×2)

but i get garbage values.

is my SIM900 not responding because i m  ot accepting the OK or is there something else . I am seriously not able to understand where the problem

can u pls help me out with dis

Thanks in advance

Sandeep

Hi Sandeep,

I guess the max232 IC circuit between the 8051 and the SIM900 is working perfectly.

I also had the same problem, it was due to some power supply connection issue when connecting with the microcontroller board, the SIM900 will respond with AT commands but not able to make a call or send message.

Please post here the exact circuit you are using right now.

First try to fix this issue and then we will look into the LCD problem.

Thanks Ajish

There is no custom ciruitary i have buit

using 8051 development board 

RS232 connection b/w 8051 board and sim900 board

data getting out of RS232 is perfectly fine as checked it in realterm.

now i am writing a small code to display data sent from hyperterminal on the LCD -> troubleshooting

how do u think power supply will be a problem?, 8051 and SIM900 working perfectly fine when used independently and the data sent to sim900 using 8051 and PC are exactly the same .

What do you think can be d problem?

Thanks

Sandeep

Hi Sandeep,

I’ve used a SIM900 based module, and by mistake I was using a 3.3V power adaptor. Still it was giving me response when I send AT comands !

But not able to make a call or send messages. 

Since you are using two seperate power supply, the ground should be properly shorted together and the two power supply should not in anyway affect each other. Just make sure using a multimeter that you are getting 5V at the output of the regulator ICs in both your development board and the GSM module.

Post your LCD code, I’ll try to figure out if there is any bug in it.

Hi Ajish ,

U suspected that there may be a power supply problem 

so I soldered two wires btw the module and now there is single power supply 

and i also chkd with the multimeter ,its perfetly fine

i can send u the code :

send a dummy mail to my id sunny2791@gmail 

i will immediately send the code to ur id

Hi Sandeep,

That’s good. Now you don’t have to worry about the hardware right!!

You can simply copy paste your code with your next post. I guess that would be far more better as you can get help or advise from other people in this forum.

Hi ajish thanks a lot for all ur replies 

I found the bug

the Tx of 8051 was getting connected to Tx of SIM900 and same with Rx , it happened because i was using a male to male connector.

now that is resolved

data recieved was seen on LCD when i used

         ch= SBUF;

         str[count++]=ch;    // used to store the data

Now wrote a code to display the stored data in str[] , which is not happening

code is:

char str[20];

Hi ajish 

I have tried a simple LCD program also , its working fine

my problem is 

serial data i/p has to put on to string say str[20] a global array

den serially display it on the LCD

so now , displaying the string on  the LCD is working fine ,but storing the serial input characters in an array is giving the problem i guess

and next,

in my main function think i am firsst displaying “hello world ”  on my LCD and then my program enters a while(1); loop

now incase i get a recieve interrupt -> it jumps to ISR gets the character and stores in th array 

and den i need to print the string but after the ISR but it goes into the while(1);

what to do ?

den i thought i will use polling method to get the data, but that seems to be a bad practice.

wat do i do now ?

Thank you

Sandeep

Hi Sandeep,

Sorry for the delayed response.

I found this from your ISR;

               }

ISR should always be very light, less time consuming and free of any function calls. Hence I suggest you to avoid the statement;