Pointers to Structures - Working Code

[Bill Legge]

I had some difficulty understanding using functions to write to a structure - so here is some working code.
Nothing new but I hope it helps you to understand structures?
Regards Bill Legge in Australia

Code: Select all

////////////////////////////////////////////////////////////////////////////////
// Project:         0000_Structures_Pointers                                  //
// Function:        Test functionjs with structures and pointers              //
// MCU:             PIC18F8722                                                //
// Board:           BigPIC5                                                   //
// Power            5V                                                        //
// Compiler:        mikroC PRO for PIC version 7.6.0                          //
// Author:          WVL                                                       //
// Date:            January 2021                                              //
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
// Function - direct PrintOut stream to UART2                                 //
void U2(char c){UART2_Write(c);}                                              //
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
struct date{   // to hold values from the RTC or GPS                          //
    char day;       // days    1 to 31                                        //
    char mon;       // months  1 to 12                                        //
    char yer;       // years   0 to 99                                        //
};                                                                            //
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
struct time{   // to hold values from the RTC or GPS                          //
    char sec;       // seconds 0 to 59                                        //
    char min;       // minutes 0 to 59                                        //
    char hrs;       // hours   0 to 23  (24-hour time)                        //
};                                                                            //
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
typedef struct position{                                                      //
    char x;                                                                   //
    char y;                                                                   //
};                                                                            //
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
// Function - pass a pointer to the structure position                        //
void update_position(struct position *my_ptr){                                //
    my_ptr->x ++;                                                             //
    my_ptr->y ++;                                                             //
}                                                                             //
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
// Function - pass a pointer to a structure time                              //
void update_time(struct time *my_ptr){                                        //
    my_ptr->sec++;                                                            //
    my_ptr->min++;                                                            //
    my_ptr->hrs++;                                                            //
}                                                                             //
////////////////////////////////////////////////////////////////////////////////


void main() {
    // Block variables
    char n = 0;
    char my_string[6];
    // create pointers and variables with structures
    struct date *PFC_date_ptr, PFC_date={11,12,13}, *GPS_date_ptr, GPS_date={11,12,13};
    struct time *PFC_time_ptr, PFC_time={21,22,23}, *GPS_time_ptr, GPS_time={21,22,23};
    // create a number of variables with the same structure
    struct position pos_1;
    struct position pos_2={1,2}, pos_3={3,4};
    pos_1.x = 33;
    GPS_date.day = 15;
    Update_position(&pos_2);
    
    // Init peripherals
    INTCON2.RBPU = 1;           // PORTB pullups disabled
    ADCON1 = 0b00001101;        // A0 and A1 are analog inputs
    CMCON  = 0b00000111;        // disable comparators
    // Init ports
    TRISD = 0b00000000;         // LEDs on PORTD active low
    UART1_Init(4800);           // UART1 on C6/tx and C7/rx
    UART2_Init(4800);           // UART2 on G1/tx and G2/rx

    // Announce
    UART2_Write_Text("\r\nTest pointers to structures\r\n");

    while(1){
        // Use a function to update a structure
        update_time(&GPS_time);
        UART2_Write_Text("GPS_time values:");
        ByteToStr(GPS_time.sec,my_string);
        UART2_Write_Text(my_string);
        ByteToStr(GPS_time.min,my_string);
        UART2_Write_Text(my_string);
        ByteToStr(GPS_time.hrs,my_string);
        UART2_Write_Text(my_string);
        UART2_Write_Text("\r\n\n");
        
        update_position(&Pos_2);
        UART2_Write_Text("Pos_2:");
        ByteToStr(Pos_2.x,my_string);
        UART2_Write_Text(my_string);
        ByteToStr(Pos_2.y,my_string);
        UART2_Write_Text(my_string);
        UART2_Write_Text("\r\n\n");
        
        delay_ms(1000);
        LATD.B0 =~LATD.B0;
    }
}

[filip]

Hi,

Nice work, I'm sure our users will find it useful !

Regards,
Filip.