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pilar
Joined: 30 Jan 2008
Posts: 197
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| How stored a float variable in the eeprom of pic |
 Posted: Fri Sep 25, 2009 4:33 pm |
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Hi need to store float variable (Valor_ADC0) in the eeprom of pic, how I can do it??
Here is my code:
| Code: |
#include <18F452.h>
#DEVICE ADC=8
#fuses HS,NOWDT,NOPROTECT,NOLVP,NOBROWNOUT
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)// RS232 Estándar
void main() {
int32 Buffer_ADC0;
float Valor_ADC0;
setup_adc_ports(AN0);
setup_adc(ADC_CLOCK_DIV_32);
set_adc_channel(0);
delay_us(10);
while (TRUE){
set_adc_channel(0);
delay_us(4);
Buffer_ADC0 = read_adc();
delay_us(10);
Valor_ADC0 = (float)Buffer_ADC0 *(0.0529);
printf("%4.2f \r\n", Valor_ADC0);
}
}
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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Ttelmah
Guest
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| Posted: Sat Sep 26, 2009 3:04 am |
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Also though, look at the write life limitations of the EEPROM.
The code shown, will probably kill the EEPROM, in a couple of hours, and 'worst case' (maximum operating temperature, and a bad chip example), could do it in under ten seconds....
The EEPROM, is _not_ designed to hold values that are changing fast/frequently. You need to rethink the approach, if you want to store a value being read fast. Either use RAM, and store it to the EEPROM, only when power goes off, or use an external memory without the limitations (FRAM).
Best Wishes |
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Guest
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| Posted: Sat Sep 26, 2009 6:16 am |
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Another option, if you're always sending it to a PC ( the print line..), is to have the PC store the data for you.
Jay |
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pilar
Joined: 30 Jan 2008
Posts: 197
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| Posted: Mon Sep 28, 2009 8:49 am |
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Hi, I tried using the examples that you refer me but I can not write or read the float data correctly in eeprom, someone could tell me what my mistake?.
The maximum value of the ADC input is 5V equivalent to 13.45.
| Code: | #include <18F452.h>
#DEVICE ADC=8
#fuses HS,NOWDT,NOPROTECT,NOLVP,NOBROWNOUT
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)// RS232 Estándar
int j;
float data;
void Write_Float_Eeprom(address, float data)
{
int8 i;
for(i = 0; i < 16; ++i){
write_eeprom(address + i, *((int8 *)(&data) + i));
}
}
float Read_Float_Eeprom( address)
{
int8 i;
float data;
for(i = 0; i < 16; ++i)
{
*((int8 *)(&data) + i) = read_eeprom(address + i);
}
return data;
}
void Init_EEprom(){
for(j = 0; j < 16; ++j){
write_eeprom(j,0xff);
}
}
void main() {
int32 Buffer_ADC0;
float Valor_ADC0;
setup_adc_ports(AN0);
setup_adc(ADC_CLOCK_DIV_32);
set_adc_channel(0);
delay_us(10);
Init_EEprom();
set_adc_channel(0);
delay_us(4);
Buffer_ADC0 = read_adc();
delay_us(10);
Valor_ADC0 = (float)Buffer_ADC0 *(0.0529);
printf("%4.2f \r\n", Valor_ADC0);
Write_Float_Eeprom(0,Valor_ADC0);
delay_us(200);
Read_Float_Eeprom(0);
printf("%4.2f \r\n", data);
while (TRUE);
} |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Mon Sep 28, 2009 9:30 am |
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Are there any indications of float occupying 16 bytes with CCS C? It doesn't, you're definitely writing out of bounds.
Also Read_Float_Eeprom() goes to nowhere in your code. |
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Ttelmah
Guest
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| Posted: Mon Sep 28, 2009 9:44 am |
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Let's explain what Fvm is saying about read_float_eeprom.
You have a global variable called 'data'. You don't write to this anywhere.
You have a local variable called 'data'. You write to this, and then to twelve more bytes in memory, 'beyond' this, potentially destroying other variables.
You then return a value in this, and don't store the return anywhere.
Not surprising if you don't see what you expect...
Best Wishes |
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pilar
Joined: 30 Jan 2008
Posts: 197
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| Posted: Mon Sep 28, 2009 9:48 am |
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| Quote: | | Are there any indications of float occupying 16 bytes with CCS C? It doesn't, you're definitely writing out of bounds |
| Quote: | How do I write variables to EEPROM that are not a byte?
The following is an example of how to read and write a floating point number from/to EEPROM. The same concept may be used for structures, arrays or any other type.
n is an offset into the eeprom.
For example if the first float is at 0 the second
For floats you must increment it by 4.
one should be at 4 and the third at 8.
WRITE_FLOAT_EXT_EEPROM(long int n, float data) {
int i;
for (i = 0; i < 4; i++)
write_ext_eeprom(i + n, *((int8*)&data + i) ) ;
}
float READ_FLOAT_EXT_EEPROM(long int n) {
int i;
float data;
for (i = 0; i < 4; i++)
*((int8*)&data + i) = read_ext_eeprom(i + n);
return(data);
}
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 I'm lost, I do not understand ??? |
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Ttelmah
Guest
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| Posted: Mon Sep 28, 2009 9:58 am |
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Look, the example shows exactly what you need. Four bytes, not 16.
Then if a function _returns_ a value, you need to retrieve this in your program. So:
your_variable=READ_FLOAT_EXT_EEPROM(0);
not just calling the function...
Then, key change that needs to be made. The example, uses the functions to talk to an _external_ eepom, you need to use the functions for the internal eeprom instead.
The functions you have written, are correct, _except_ for trying to use 16bytes, instead of 4, and you are not reading the returned value.
Best Wishes |
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pilar
Joined: 30 Jan 2008
Posts: 197
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| Posted: Mon Sep 28, 2009 10:18 am |
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 hi Ttelmah, thank you, now it is working.... |
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pilar
Joined: 30 Jan 2008
Posts: 197
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| Posted: Mon Sep 28, 2009 10:55 am |
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Sorry by my insistence, but now I need to convert this float value to a string Valor. I tried to use the itoa but I can not get the correct value. Which is my mistake?
| Code: |
char Valor[6];
.
.
.
Write_Float_Eeprom(0,Valor_ADC0);
delay_us(200);
buffer = Read_Float_Eeprom(0);
itoa(buffer,10, Valor);
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Ttelmah
Guest
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| Posted: Mon Sep 28, 2009 12:25 pm |
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The 'i', in 'itoa', is for _integer_....
You can sprintf to a string, or for a fixed precision (faster), multiply your float by (say) 100, and convert this to integer, then just add a decimal point (for sprintf, look at %w).
Best Wishes |
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pilar
Joined: 30 Jan 2008
Posts: 197
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| Posted: Mon Sep 28, 2009 2:27 pm |
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| thanks.. |
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