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Altera_Forum's avatar
Altera_Forum
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16 years ago

Problem with reading from Uart

I am getting the following warnings when I build my project

passing arg 1 of `fgets' from incompatible pointer type

passing arg 1 of `fgets' makes pointer from integer without a cast

The call to fgets is as follows...

fgets( Sonar_Height , 4 , fp_uart);

Sonar_Height is declared as a character array of size 3

char* Sonar_Height [3]

fp_uart is the name of the file pointer to my uart

Also i am getting the following warning

char format, pointer arg (arg 2)

Call to printf is as follows...

printf( "Initial Sonar Height: %s\n" , Sonar_Height);

Sonar_Height is the same variable as in fgets call.

What do these warnings mean? Could they be the reason my read attempts from uart fail?

Any assistance will be appreciated

Chase

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Hi Chase,

    fgets requires a char* (pointer to char) as first parameter.

    Your Sonar_Height variable is a char** (pointer to a pointer to char).

    In order to have a 3 char array you must change to:

    char Sonar_Height [3];
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    You also need to change this to: 

    
char Sonar_Height ;
    fgets stores a NUL in the last position and you called fgets with a count of 4. When it writes the 0 to Sonar_Height [3] you will overwrite a byte, possibly the return address crashing this function.

    Bill
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    I see my mistake now. Thanks guys for your help it is much appreciated :)