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t90
Joined: 07 Aug 2008
Posts: 11
Location: saigon,vietnam
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| How to change the value of the array via function? |
 Posted: Tue Dec 02, 2008 2:09 am |
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I work in project that use PIC18f4550. In my project I implement one function to copy value from 1 variable to 1 member in 1 array consist 20 member which 1 member is a char variable has 4 member. But I can't copy the value. Someone has seen my problem. please solve for me. Thank you!
Here my code:
| Code: | //my array
struct Node{
int time[4];
};/**/
static struct Node tim[20];
static BYTE temp[4];
//function copy
void bcopy(int a[4],int &b0,int &b1,int &b2,int &b3){
b0=a[0];
b1=a[1];
b2=a[2];
b3=a[3];
return;
}
//another function copy
void bcopy1(int8 a[4]){
temp[0]=a[0];
temp[1]=a[1];
temp[2]=a[2];
temp[3]=a[3];
return;
}
void main(){
int a1[4];
int a2[4];
int a3[4];
int a4[4];
int a5[4];
int a6[4];
a1[0]=0x00;
a1[1]=0x00;
a1[2]=0xFF;
a1[3]=0x7F;
a2[0]=0x00;
a2[1]=0x01;
a2[2]=0x02;
a2[3]=0x03;
//the value not change bcopy(a1,tim[header].time[0],tim[header].time[1],tim[header].time[2],tim[header].time[3]);
//the value not change
bcopy(a1,temp[0],temp[1],temp[2],temp[3]);
} |
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Ttelmah
Guest
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| Posted: Tue Dec 02, 2008 3:40 am |
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You don't say 'what compiler version'.
Now, you are using reference parameters, which are a sort of 'halfway house', between using pointers, and the normal pass by value. I'd not use reference paramters for this. The manual says _limited support_ for reference parameters, and though they do work for a simple variable, for an array item, I'd not be at all surprised if they gave trouble.
I'd stick to 'standard' C, and pass the addresses.
So:
[code]
//function copy
void bcopy(int a[4],int * b0,int * b1,int * b2,int * b3){
*b0=a[0];
*b1=a[1];
*b2=a[2];
*b3=a[3];
}
//and call with
bcopy(a1,&temp[0],&temp[1],&temp[2],&temp[3]);
[/copy]
Best Wishes |
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Wayne_
Joined: 10 Oct 2007
Posts: 681
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| Posted: Tue Dec 02, 2008 3:45 am |
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You need to pass the address of the var/array you want to set to the function, I think you have gotten a little confused about pointers. As you are using arrays a better method would be:-
| Code: |
void bcopy(int *a, int *b) // This function requires 2 pointers
{
int i;
for (i = 0; i < 4; i++)
{
b[i] = a[i]; // or *b++ = *a++; should work as well
}
}
void main(){
int a1[4];
int a2[4];
int a3[4];
int a4[4];
int a5[4];
int a6[4];
a1[0]=0x00;
a1[1]=0x00;
a1[2]=0xFF;
a1[3]=0x7F;
a2[0]=0x00;
a2[1]=0x01;
a2[2]=0x02;
a2[3]=0x03;
bcopy(a1, tim[header].time); // pass the address of a1 and tim[header].time ti the function
bcopy(a1, temp); // pass the address of a1 and temp
// Specifying just the name of the array will pass the address of that array
// Some people prefer to use
// bcopy(&a1[0], &temp[0]); // & means address of so &a1[0] is the address of the first index of the array
}
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t90
Joined: 07 Aug 2008
Posts: 11
Location: saigon,vietnam
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| Posted: Tue Dec 02, 2008 8:55 am |
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Thank you very much! But the values displayed in LCD isn't values I have input in my array. Here is my entire code. Please see it for me!.
| Code: | #include "18f4550.h"
#device HIGH_INTS=TRUE
#use delay(clock=20000000)
#fuses HS,NOPROTECT,NOLVP,NODEBUG,NOWDT
#use rs232(baud=9600, xmit=PIN_C6,rcv=PIN_C7)
#include "ewl_glcd.c"
#include "ewl_realtime.c"
char glcd_buff[128];
int a[4];
char out[10];
struct Node{
int time[4];
};/**/
static struct Node tim[20];
void bcopy(int *a, int *b) // This function requires 2 pointers
{
int i;
for (i = 0; i < 4; i++)
{
*b[i]++ = *a[i]++; // or *b++ = *a++; should work as well
}
}
// External interrupt xac dinh boi tin hieu goi ve tu chip RealTime clock
#int_ext2
void rtc_card_isr()
{
read_time();
glcd_fill_area(0,0,127,12,OFF);
sprintf(glcd_buff,"%Lu-%u-%u %U:%02U:%02U\n",2000+ds1307_regs[YEAR_REG],ds1307_regs[MONTH_REG],
ds1307_regs[DATE_REG],ds1307_regs[HOURS_REG],ds1307_regs[MINUTES_REG],ds1307_regs[SECONDS_REG]);
glcd_text57(0,0,glcd_buff,1,ON);
}
void main()
{
int header;
int c[4];
set_time();
header=0;
a[0]=1;
a[1]=2;
a[2]=3;
a[3]=4;
c[0]=0xFF;
c[1]=0xFF;
c[2]=0x01;
c[3]=0x01;
set_tris_e(0x00);
set_tris_d(0x00);
set_tris_b(0xfc);
set_tris_c(0b10000000);
setup_adc(ADC_OFF);
set_tris_a(0x00);
///////////////
glcd_init(ON);
glcd_fillScreen(OFF);
// LCD
set_tris_c(get_tris_c()&0b11111011);
setup_timer_2(T2_DIV_BY_16,127,1);
setup_ccp1(CCP_PWM);
set_pwm1_duty(500);
bcopy(a,tim[1].time);
enable_interrupts(INT_EXT2);
enable_interrupts(GLOBAL);
init_DS1307();
//set_tris_b(get_tris_b() | 0xF0);
set_tris_e(0x00);
sprintf(out,"%u-%u-%u-%u ",tim[1].time[0],tim[1].time[1],tim[1].time[2],tim[1].time[3]);
while(1){
glcd_text57(0,30,out,1,ON);//display the value in graphic LCD but the value is wrong.
}
} |
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Wayne_
Joined: 10 Oct 2007
Posts: 681
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| Posted: Tue Dec 02, 2008 9:01 am |
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You have changed the line
*b[i]++ = *a[i]++; // or *b++ = *a++; should work as well
It should be
b[i] = a[i];
or
*b++ = *a++;
Not a mixture of both! |
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t90
Joined: 07 Aug 2008
Posts: 11
Location: saigon,vietnam
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| Thank you Wayne_ |
| Posted: Tue Dec 02, 2008 9:49 pm |
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| It's well active. Thank you! |
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