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ac34856
Joined: 14 Dec 2009
Posts: 33
Location: Wales
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| Writing Setup Structure to Data EEPROM |
 Posted: Wed Jan 20, 2010 10:04 am |
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I am trying to get some code to work to write and read a data
structure from the PIC data eeprom. I've snipped lots out
but the bones are below.
It obviously isn't working but does anyone know what the
problem is ? I need to copy string data to a structure but
the structure doesn't like copy via the char * pointer.
Thanks in advance
| Code: |
#include <18F4620.h>
#device PASS_STRINGS=IN_RAM
#device *= 16;
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <stdlibm.h>
const char CHANNEL[]={"PID Channel 1 - PP Control"};
struct PID {
char ident[sizeof(CHANNEL)];
float Kp, Ki, Kd ; //
float rate ; // Ramp rate in KPa/min
float rsp ; // Ramping SP MPa.
float tsp ; // Target SP in MPa.
float mv ; // Read as zero at startup
float pb ; // Proportional band in KPa.
float mverr ; // MV Error - not stored.
BOOL fwd ; // Forward or reverse PID
BOOL s_ok ;
} trx, *ptrx ;
// declaration of structure and pointer to an instance of this
void read_eeprom_string(char *array, int8 address, int8 max_size)
{
int8 i = 0;
*array = 0;
while(i<max_size)
{ *array=read_eeprom(address+i);
if (*array==0) { i=max_size; }
else { array++;
*array=0; } i++;
}
}
//*******************************************
// Function: write_eeprom_string
//*******************************************
void write_eeprom_string(char *array, int8 address, int8 max_size)
{
int8 i=0;
while(i < max_size) { write_eeprom(address+i, *array);
if (*array==0) { i=max_size; }
array++; i++;
}
}
// Start of main ..
void main()
{
trx.Kp = 10;
trx.Ki = 20;
trx.Kd = 35;
ptrx = &trx;
EOB = sizeof(trx)+2;
write_eeprom_string((char *) ptrx, 0, EOB);
read_eeprom_string( (char * )ptrx, 0, EOB);
// etc.
// fprintf("\r\n Ki=%f Kp=%f Kd=%f, trx.Kp, trx.Ki, trx.Kd);
} |
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Ttelmah
Guest
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| Posted: Wed Jan 20, 2010 10:15 am |
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Won't work reliably.
The problem is that the 'string' functions will terminate, when they see a '0' byte (end of string marker in C), in the array....
Make the functions generic, so something like:
| Code: |
//EPROM save/retrieve routines.
void EEPROM_GET(int *ptr,int num,int addr) {
int count;
for (count=0;count<num;count++)
{
ptr[count]=READ_EEPROM(addr+count);
}
}
void EEPROM_PUT(int *ptr,int num,int addr) {
int count;
for (count=0;count<num;count++)
{
WRITE_EEPROM(addr+count,ptr[count]);
}
}
//Then in your case:
EEPROM_PUT(&trx,sizeof(STRUCT PID),0);
//and to read
EEPROM_GET(&trx,sizeof(STRUCT PID),0);
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You also have another problem, since you may transfer two bytes _beyond_ the array (if a 0 marker is not met), which depending on luck, may/will be another variable, resulting in this being corrupted.
Best Wishes |
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