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jmann
Joined: 27 Dec 2004
Posts: 21
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| Char Stars not passing to functions |
 Posted: Wed Apr 13, 2005 7:01 pm |
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I cannot get a variable to pass to a function as a pointer.
for example, I call:
| Code: | JeffSend(SomeString, 100);
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in which the function is:
| Code: | int16 JeffSend(char *data, int16 len)
{
//some code
}
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but in the function, data is 0x0000, it is not the location of SomeString
Any idea why? SomeString is a gobally decleared array of char, i.e.: a string (and is not a constant). |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Wed Apr 13, 2005 7:30 pm |
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This has always worked, so likely the problem is in your code. There are several things that can be wrong therefor please post a small but complete working program showing your problem.
Also mention the compiler version you are using. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Apr 14, 2005 1:06 pm |
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Here is a test program that shows how to do it. This was tested with
PCM vs. 3.222. The output on the terminal window is:
Hello World
| Code: |
#include <16F877.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
void display_string(char *ptr)
{
printf("%s", ptr);
}
//===================
void main()
{
char array[20];
strcpy(array, "Hello World \n\r");
display_string(array);
while(1);
} |
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jmann
Joined: 27 Dec 2004
Posts: 21
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| Posted: Fri Apr 15, 2005 4:09 am |
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when send-in calls writenetwork, data should have the value of 0x015F (the location of wr_ptr), however it gets the value 0x0020.
compiler Version 3.207 target chip 18F452
(also, I know that endian is reversed between the two devices I am trying to use, so void endian(int32) reverses endian after and before writing, but that is not important to this problem)
| Code: | //-----------------------------------
//Preform a sequential write
//-----------------------------------
int1 WriteNetwork(int16 Addr, char* Data, int16 len)
{
int16 i;
char Err = NOERROR;
I2CInterrupts(DisableI2C);// Disable Interrupt
i2c_start(); // START Signal Of Address
if(i2c_write(W3100Awrite)==NoError &&
i2c_write(make8(addr,1))==NoError && //address MSD
i2c_write(make8(addr,0))==NoError ) //address LSD
{
for(i = 0 ; i < len ; i++)
if(i2c_Write(*Data++)==ERROR)
{
err=ERROR;
break;
}
}
else //error occured
{
err=ERROR;
}
i2c_stop(); // STOP Signal Of Address
I2CInterrupts(EnableI2C);// Enable Interrupt
return Err;
} |
| Code: | int16 send_in(char* data, int16 len)
{
char k;
signed int16 size;
int32 wr_ptr, ack_ptr;
int16 address;
S_START:
// I2CInterrupts(DisableI2C);
ReadNetwork(SHADOW_TXWR_PTR(0), wr_ptr, 3); // Must read the shadow register for reading 4byte pointer registers
delay_us(2); // wait for reading 4byte pointer registers safely
ReadNetwork(TX_WR_PTR(0), wr_ptr, 4);
endian(wr_ptr);
ReadNetwork(SHADOW_TXACK_PTR(0), ack_ptr, 3); // Must read the shadow register for reading 4byte pointer registers
delay_us(2); // wait for reading 4byte pointer registers safely
ReadNetwork(TX_ACK_PTR(0), ack_ptr, 4);
endian(ack_ptr);
// I2CInterrupts(EnableI2C);
// Calculate send free buffer size
if ((wr_ptr&SMASK) >= (ack_ptr&SMASK))
size = SSIZE - ((wr_ptr&SMASK) - (ack_ptr&SMASK));
else
size = SSIZE - (0 - (ack_ptr&SMASK) + (wr_ptr&SMASK));
if (size > SSIZE) // Recalulate after some delay because of error in pointer caluation
{
if (ReadNetworkRegister(SOCK_STATUS(0)) != SOCK_ESTABLISHED) return 0; // Error
delay_ms(1);
goto S_START;
}
if (size == 0) // Wait when previous sending has not finished yet and there's no free buffer
{
if (ReadNetworkRegister(SOCK_STATUS(0)) != SOCK_ESTABLISHED) return 0; // Error
delay_ms(1);
goto S_START;
}
else if (size < len) len = size;
address = (int16)( SEND_DATA_BUF + ((int16)(wr_ptr)) & SMASK); // Calculate pointer to data copy
WriteNetwork(address, data, len); // data copy
while (WriteNetworkRegister(COMMAND(0), CSEND)) // Confirm send command
if (ReadNetworkRegister(SOCK_STATUS(0)) != SOCK_ESTABLISHED) return 0; // Error
wr_ptr = wr_ptr + len;
endian( wr_ptr); // tx_wr_ptr update
WriteNetwork(TX_WR_PTR(0), wr_ptr, 4);
WriteNetworkRegister(COMMAND(0),CSEND); // SEND
return (len);
} |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Fri Apr 15, 2005 6:12 am |
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Take a look at these three statements. Data is defined as a pointer to a char. wr_ptr is defined as int32 and you are not even calling the function with the address of wr_ptr but using the value. I can see why you are having problems.
| Code: |
int1 WriteNetwork(int16 Addr, char* Data, int16 len)
int32 wr_ptr, ack_ptr;
WriteNetwork(TX_WR_PTR(0), wr_ptr, 4);
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jmann
Joined: 27 Dec 2004
Posts: 21
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| Posted: Sat Apr 16, 2005 9:27 am |
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but a pointer is a pointer, right?
then wouild this work?:
| Code: | int16 send_in(char* data, int16 len)
{
char k;
signed int16 size;
int32 wr_ptr, ack_ptr;
int16 address;
char* pointer;
pointer = (&wr_ptr); //make pointer point to the location of wr_ptr
WriteNetwork(TX_WR_PTR(0), pointer, 4); //now call function with a pointer pointing of the same type
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I know it is little endian, and would have to deal with that. |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Sat Apr 16, 2005 12:35 pm |
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All you need is
| Code: |
WriteNetwork(TX_WR_PTR(0), &wr_ptr, 4);
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but
| Code: |
WriteNetwork(TX_WR_PTR(0), (char*)&wr_ptr, 4);
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is more correct |
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Guest
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| Posted: Sat Apr 16, 2005 4:04 pm |
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| thank you, I am making those changes. |
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