Warnings I cannot understand after compilation-Part1

Hmm, the warnings have nothing to do with embedded development. This is basic C stuff.

'func' undefined; assuming 'extern int func()' means what it says: the compiler encountered a call to a function which has not been declared yet. Functions should be declared before called, otherwise you are asking for trouble.

'func': no return value means that although the function definition says it returns a value, there is no return statement in the function body.

Time to read up on the C programming language.

Hmm, the warnings have nothing to do with embedded development. This is basic C stuff.

'func' undefined; assuming 'extern int func()' means what it says: the compiler encountered a call to a function which has not been declared yet. Functions should be declared before called, otherwise you are asking for trouble.

'func': no return value means that although the function definition says it returns a value, there is no return statement in the function body.

Time to read up on the C programming language.

Mike, Appreciate your response. However at the end of currentRT and RTC_CAN functions if I insert a return statement I still continue to get the warnings. I tried changing the functions from void to 'int' and it does nothing.

Note that 3 of the 5 warnings have nothing to do with return values anyhow - so you should not expect this to fix those ones!

If "adding a 'return' statement" doesn't fix the other 2 warnings (the ones about return values), then you must be doing it wrong.
You would obviously need to post the code for anyone to be able to see exactly what you're doing wrong...

 while(1)
 {
        extern currentRT();
        if (T3>=19532) //1s timer
                {
                        CAN_NQS_time_date();
                        T3 = 0;
                }

 }

Why your "extern"? Are you trying to declare that there exists a function currentRT(), or are you calling the function?

Similarly for:

extern void timer1s(void)
{

unsigned int time_count;

As Mike said initially, it looks like time for some "back to basics" with the 'C' textbook...

See also: c-faq.com/.../decldef.html

Per, I am trying to say that a function called currentRT() exists in another module (RTC.c). Anyway I decided to download the program anyway as I had no errors. What I noticed is that after the RTC ticks over to 9:06:09 (i.e 9:06 and 09 seconds) I get garbage values. I have checked it a few times and everytime while transitioning from 9:06:08 to 9:06:09 something happens and I keep getting garbage values. Can anyone tell me what is going on? If there is some overflow issue how do I get around it?

You are trying to say that a function currentRT() exists in another module. But why, unless you where planning on also call the function?

Are you really sure that you have the correct time when you get into troubles?

9:06:08 = 9*3600 + 6*60 + 8 = 32768 = 0x8000.
9:06:07 = 9*3600 + 6*60 + 7 = 32767 = 0x7fff.

How big numbers to you think you can store in a signed 16-bit integer? I would kind of guess at -32768 .. +32767.

If you change to an unsigned integer, you will get 0 .. 65535 which corresponds to 00:00:00 .. 18:12:15.

So it seems like you have to switch to a long 32-bit value to keep track of your time. There are 86400 seconds in 24 hours.

Just a footnote: Old MS-DOS (FAT directory entries) only stored even seconds for the file time stamp, just to get the clock value to fit in a 16-bit unsigned integer.

Just a footnote: Old MS-DOS (FAT directory entries) only stored even seconds for the file time stamp, just to get the clock value to fit in a 16-bit unsigned integer.

It makes you think: MS do get some things right :-)

Thanks. Will try it out. I am sure that was my mistake.

Ok.So here we go again. The RTC now resets when the the clock is 18:12:15 (=65,535) which is telling me that the problem could be that the size I am assigning to store the register values is smaller than I need. I checked and I am storing the register values in 'unsigned long' which should hold more than 65,535. Here's the code:

#include "REG164.h"
#include "RTC_C16x.h"
#include "MATH.H"
struct temptime
{
        int daysa;
        int daysb;
        int hour;
        int minute;
        int seconds;
    int day;
        int month;
        int year1;
        int year2;
}time;
unsigned long RTCvalue;
int current_day = 6;
int current_month = 10 ;
int current_year = 2008;
union _32bit
{
        unsigned long rtcreg[1];
        unsigned long a;
} RTC;


void RTC_CAN(void)
{
//check for month and then either reset or increment day
        switch (current_month){
                                        case 1:
                                        case 3:
                                        case 5:
                                        case 7:
                                        case 9:
                                        case 11:
                                                        if(current_day == 32)
                                                                {
                                                                        current_day=1;
                                                                        current_month = current_month+1;

                                                                }

                                        case 4:
                                        case 6:
                                        case 8:
                                        case 10:
                                        case 12:
                                                        if(current_day == 31)
                                                                {
                                                                        current_day = 1;
                                                                        current_month = current_month+1;
                                                                        if(current_month==13)
                                                                                {
                                                                                        current_month=1;
                                                                                        current_year=current_year+1;
                                                                                 }
                                                                }
                                        case 2:
                                                        if(current_day == 29)
                                                                {
                                                                        current_day = 1;
                                                                        current_month = current_month+1;
                                                                }

                                  }


//mapping what needs to be transmitted on CAN(BCD value) and it's decimal equivalent.

        if(time.hour<=9)
                {
                        time.hour = time.hour;
                }
        else if(time.hour>=10 && time.hour<=19)
                {
                        time.hour = time.hour+6; //hex 10=dec16, hex 11=dec17...hex19=dec25
                }
        else if(time.hour>=20 && time.hour<=24)
                {
                        time.hour = time.hour+12; //hex 20=dec32....hex 24=dec36
                }


        if(time.minute<=9)
                {
                        time.minute = time.minute;
                }
        else if(time.minute>=10 && time.minute<=19)
                {
                        time.minute = time.minute+6;
                }
        else if(time.minute>=20 && time.minute<=29)
                {
                        time.minute = time.minute+12;
                }

        else if(time.minute>=30 && time.minute<=39)
                {
                        time.minute = time.minute+18;
                }
        else if(time.minute>=40 && time.minute<=49)
                {
                        time.minute = time.minute+24;
                }
        else if(time.minute>=50 && time.minute<=59)
                {
                        time.minute = time.minute+30;
                }

        if(current_day<=9)
                {
                        time.day=current_day;
                }
        else if(current_day >=10 && current_day<=19)
                {
                        time.day=current_day+6;
                }
        else if(current_day >=20 && current_day <=29)
                {
                        time.day=current_day+12;
                }
        else if(current_day >=30 && current_day <=32)
                {
                        time.day = current_day+18;
                }


        if(current_month<=9)
                {
                        time.month = current_month;
                }
        else
                {
                        time.month = current_month+6;
                }

        if(current_year==2008)
                {
                        time.year1=32;
                        time.year2=8;
                }
        else if(current_year==2009)
                {
                        time.year1=32;
                        time.year2=9;
                }
        else if(current_year==2010)
                {
                        time.year1=32;
                        time.year2=16;
                }

}


void RTCinit(void)
{

        RTCL = 0; //clearing lower RTC register
        RTCH = 0; //clearing higher RTC register
        RTCvalue = (18*3600) + (10*60)+30;
        RTC.a = RTCvalue;
        RTCL = RTC.rtcreg[0];
        RTCH = RTC.rtcreg[1];
        T14REL = 0xB3B5;
        timer1s();
}
void currentRT(void)
{
        unsigned int x,y,z;

        RTC.rtcreg[0] = RTCL;
        RTC.rtcreg[1] = RTCH;
        RTCvalue = RTC.a;
        x = RTCvalue/86400;
        time.daysa = floor(x);
        RTCvalue = RTCvalue-(time.daysa*86400)
        time.daysb = 0;
        if(time.daysa>time.daysb)
                {
                        current_day = current_day+1;
                }
        time.daysb = time.daysa;
        y = RTCvalue/3600;
        time.hour = floor(y);
        RTCvalue = RTCvalue-(time.hour*3600);//extracting the hour information
        z = RTCvalue/60;
        time.minute = floor(z);
        RTC_CAN();
}
//end of RTC_CAN

1) The constant 86400 is too large for an integer. You should write 86400ul to specify that the constant is an unsigned long.

2) You are doing forbidden things with your RTC union. Exactly how do you think that two 32-bit integers (one part of the union - or more specifically: what you think is two long numbers) should fit in the other part of the union?

To declare an array of two elements (with index 0 and 1), you have to write rtcreg[2].

But if the RTC registers are 16-bit values, then it is meaningless to try and play with two 32-bit destination entries. Especially since it takes two 16-bit integers to concatenate to a single 32-bit integer - your expected end result.

3) Why do you use a floating--point function - floor() - with integer variables. What fractions do you think the integer x may contain?

x = RTCvalue/86400;
time.daysa = floor(x);

Let me answer your questions:

1. Are you saying that the code should look like:

x = RTCvalue/86400ul;

Interesting
2. I was just changing the unsigned long reg[1] to just unsigned int as you perhaps wrote. For some reason the timer registers being 32 bits long was stuck in my head. I just re-read the documentation.
3. If the number of hours becomes>24 the number of seconds stored in the time register will become >86400. Therefore if I divide that value by 86400 and then take the floor() of that value I will end up with 1 indicating 24 hrs has elapsed and therefore I need to increment my day. I will end up with 1,2,3... by taking the floor() which is why I compare the current value to previous. If current>previous I just increment the day value.

1) Yes, you should be explicit with large constants by adding the type suffix.

2) Yes, you should switch to unsigned or unsigned int (same thing) for the array - but you should also modify the array to have two entries, i.e. reg[2] instead of reg[1].

3) Let me repeat myself: What fractions do you think the integer x may contain?

floor() is a function used to remove the fractional part from a floating point number.

3.0 / 2.0 => 1.5. floor(1.5) => 1.

But what fractional parts do you think an integer can have?

3 / 2 => 1

Since x is unsigned int, there can not be any fractions and hence nothing for floor() to strip away...

By the way - incrementing the day is only correct if currentRT() is called at least once / 24 hours. If called more seldom, then you may have stepped more than one day.

You might do:

while (time.daysa > time.daysb) {
    time.daysb++;
    current_day++;
}

or

if (time.daysa > time.daysb) {
    current_day += (time.daysa - time.daysb);
    time.daysb = time.daysa;
}