Discussion in "8051 Discussion Forum" started by    romel_emperado    Nov 3, 2010.
Mon Jan 10 2011, 11:11 PM
nice one guys! Haha

python is weird language but good...
Tue Jan 11 2011, 05:55 PM
do let me know when you make some progress
Tue Jan 11 2011, 11:59 PM
sure ajay. But its very difficult to make a progress hehe.
i have a based code but it is in tcl language my big problem is converting it to python. Wtf! Hehe

i cant get a help here since you don know tcl and python.
Wed Jan 12 2011, 12:01 AM
later i will attach the complete source code i will let you see what is tcl language..
Wed Jan 12 2011, 10:05 AM
guys what do you mean by this

struct br
	BlueRobin_state_t 	state;
	BlueRobin_update_t	update;
	// Chest strap ID	
	u32	cs_id;

	// User settings
	u8 		user_sex;
	u16		user_weight;
	// Heart rate (1 bpm)
	u8 		heartrate;
	// Calories (1 kCal) - calculated from heart rate, user weight and user sex
	u32 	calories;
	// Speed (0.1 km/h) - demo version range is 0.0 to 25.5km/h 
	u8 		speed;
	// Distance (1 m)
	u32 	distance;
	// 0=display calories, 1=display distance
	u8		caldist_view;
extern struct br sBlueRobin;

what do you mean by this extern struct br sBlueRobin;

and i found a function looks like this

if (sBlueRobin.caldist_view == 0) 	sBlueRobin.caldist_view = 1;
	else								sBlueRobin.caldist_view = 0;

it seems that it calls the variable sBlueRobin.caldist_view

but why using "." or dot

when i will use struct br ??? what is br? is it variable?

when i declar a variable like this
s32 weight;

what do the s32 mean?? hehe i need explaination.. Im using that in my code without understanding i just seen that in some examples in the web.. hehe

[ Edited Wed Jan 12 2011, 12:26 PM ]
Wed Jan 12 2011, 12:08 PM
actually Im using that code above. I modified it and its working fine... i just used that without understanding and now i need someone to explain that to me.... hehehe eheheh thanks in advance..... heheh

Wed Jan 12 2011, 02:48 PM
thats how structures in C/C++ are used. it looks like you never used structure.
here is a quick reference

Defining structure
//defining structure
struct mystruct {
    int a;
    char b;
    char c[10];
    int d[10];

Now mystruct is name of structure. a,b,c and d are members of structure. its like grouping set of variables in a single datatype and giving your own name to it.

to use a structure, you first need to create an instance of the structure. and members of structure can only be accessed through that instance.

//defining instance of struct
struct mystruct x,y,*z;

so x and y are two instances of structure. and z is a pointer to mystruct.

using structure is very simple, lets say you want to equate members of structure x with y then you will do like this.
x.a = y.a;
x.b = y.b;

memcpy(x.c, y.c, 10); //copy character array

Pointers work a little different way we use dot (.) incase of structure variables to access the members but incase of pointers we use arrows (->) e.g.
z = &x; //z has address of x, or say z points to x now.
y.a = z->
a; //you see the difference now?
y.b = z->
//its same with all.. just replace . with ->

Initializing structure:
structures are initialized just like we do in arrays. each member is separated by comma and complete thing is enclosed in curly brackets.
x = {10, 'c', "hello", {10,20,30,40,50,60,70,80,90,100}};

//partially defining structure
y = {30, 'y', "world"};
//now the integer array  will automatically be initialized to 0.

Working example:
lets take an example, I want to make database of user accounts in C. I can have total of 100 users. user info will have username, password, age etc. so if you just do it in traditional style what you will do is.. you will create three arrays to store information of each user.
//array style..
char username[100][20]; //100 usernames each of length 20 max
char password[100][15]; //100 passwords each of length 15 max
int age[100]; //array to store age of 100 users

now if you write code using the above style you will have to manage lot of arrays which might get your code look very complex. So now lets see structure style for the same..
struct users {
char username[20];
char password[15];
int age;

that defines a custom data type with name users. now lets create 100 users.

struct users user[100];
//we define array of 100 1 structure for each user.

lets make simple login checker now.. a function that checks if entered user details are correct or not.

int checkuser(struct users input){
    int i;
    int status = 0;
    //we have 100 users so loop will go from 0 to 99
    //checking each user..
    for(i=0; i<100; i++){
        if(strcmp(input.username, user[i].username) == 0){ //check if username is there in database or not
            if(strcmp(input.password, user[i].password) == 0){ //check if password matches
                status = 1; //set status to 1 so that we say input user is available in database
                break; //break out of loop, we are done with checking
            } else {
                status = -1; //username is there but password incorrect
                break; //break out of loop.
    if(i == 100){
        //if i reaches 100 it means username not available in database
	status = -2;
    return status; //return status to caller function

well i think small tutorial on structures is good enough hope you now learn how to use structures, how to pass structure as a varaible to function, defining a structure pointer and variable etc.
 romel_emperado like this.
Tags structures in cusing structure in embedded cembedded c and structuresdata structures in embedded cembedded c tutorial structures
Thu Jan 13 2011, 05:37 AM
thank you very much ajay.. your tut is very detailed and understandable... thanks for your effort yar!!! heheeh I love u... hehe
Thu Jan 13 2011, 01:43 PM
how about this ajay


i know how to use #define varName but what is this
Fri Jan 14 2011, 03:17 PM
guys i need help again... How do i call the function mx_cal(); ?? what is that u8 line parameter? i dont have idea how do i call that from the function i made below which is burned_cal();

// system
#include "project.h"

// driver
#include "display.h"
#include "ports.h"

// logic
#include "romel.h"
#include "clock.h"
#include "date.h"
#include "user.h"

// Global Variable section
struct br mel;
s8 weight2, time;
s8 met2;
float kcal;

// Prototypes section

void display_romel(u8 line, u8 update)
		display_chars(LCD_SEG_L2_5_0, (u8 *)" CAL0", SEG_ON);

void mx_cal(u8 line)
	u8 select;
	s32 weight;
	s32 met;

	// Clear display
	// Convert global variables to local variables
	//kcalories 	=      mel.calories/1000;
	met		    =      mel.met_value/1000;
	if (sys.flag.use_metric_units)	weight = mel.user_weight;
	else							weight = ((s32)mel.user_weight * 2205) / 1000; // Convert kg to lb

	// Init value index
	select = 0;
		// Loop values until all are set or user breaks	set
		// Idle timeout : exit without saving 
		if (sys.flag.idle_timeout) break;

		// Button STAR (short): save, then exit 
		if (button.flag.star) 
			// Store local variables in global structure
			//mel.calories 	= kcalories*1000;
			//mel.user_sex 	= sex;
			mel.met_value		= met*1000;
			if (sys.flag.use_metric_units)	mel.user_weight = weight;
			else							mel.user_weight = (weight * 1000) / 2205;
			// Set display update flag
			display.flag.line1_full_update = 1;


		switch (select)

			case 0:	// Set user weight
						if (sys.flag.use_metric_units)
							display_chars(LCD_SEG_L2_1_0, (u8 *)"KG", SEG_ON);
							set_value(&weight, 3, 2, USER_WEIGHT_MIN_KG, USER_WEIGHT_MAX_KG, SETVALUE_DISPLAY_VALUE + SETVALUE_NEXT_VALUE, LCD_SEG_L2_4_2, display_value1);
							display_chars(LCD_SEG_L2_1_0, (u8 *)"LB", SEG_ON);
							set_value(&weight, 3, 2, USER_WEIGHT_MIN_LB, USER_WEIGHT_MAX_LB, SETVALUE_DISPLAY_VALUE + SETVALUE_NEXT_VALUE, LCD_SEG_L2_4_2, display_value1);
							weight2 = weight;
						select = 1;
			case 1:   //Set MET
						display_chars(LCD_SEG_L2_1_0, (u8 *)"ME", SEG_ON);
						set_value(&met, 3, 2, USER_WEIGHT_MIN, USER_METS_MAX, SETVALUE_DISPLAY_VALUE + SETVALUE_NEXT_VALUE, LCD_SEG_L2_4_2, display_value1);
						met2 = met;
						select = 0;


	// Clear button flags
	button.all_flags = 0;

//calorie expernditure forMULa

void burned_cal(void)
		if(sTime.second == 60)
		kcal = ((met2 * 3.5 * (weight2/2.2)) / 200) * time;

[ Edited Sat Jan 15 2011, 08:09 AM ]

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