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ThomasC
Joined: 09 Oct 2007
Posts: 62
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| How to write to EEPROM? |
 Posted: Thu Nov 15, 2007 2:55 pm |
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| I've done searches, looked at the examples and drivers directories, and looked at the CCS manual, but I do not understand how to write to EEPROM. What address or location do I use? I have a PIC16F690 and PCM. Thanks! |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Nov 15, 2007 3:22 pm |
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Here is a demo program for accessing internal eeprom in the 16F690.
It shows how to write and read to the eeprom with the built-in CCS
functions, write_eeprom() and read_eeprom(). It also shows how to
initialize the eeprom to specific values when the PIC is programmed
by a programmer. This is done with a #rom statement.
Here is the program output:
| Quote: |
Start
00 01 02 03 04
Wrote 0x55 to eeprom address 10
Read 55
Wrote 0xAA to eeprom address 10
Read AA
Done
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| Code: |
#include <16F690.h>
#fuses INTRC_IO, NOWDT, BROWNOUT, PUT, MCLR
#use delay(clock=8000000)
#use rs232(baud=9600, xmit=PIN_B7, rcv=PIN_B5, ERRORS)
// These eeprom locations will be written when the
// PIC is programmed with the ICD2 programmer.
#rom 0x2100 = {0, 1, 2, 3, 4} // 0x2100 is for 16F-series PICs
//==========================
main()
{
int8 i;
printf("Start\n\r\n\r");
// Display eeprom that was written with the ICD2.
for(i = 0; i < 5; i++)
printf("%x " read_eeprom(i));
printf("\n\r");
// Write 0x55 to eeprom at run-time and read it back.
write_eeprom(10, 0x55);
printf("Wrote 0x55 to eeprom address 10\n\r");
printf("Read %X\n\r", read_eeprom(10));
printf("\n\r");
// Write 0xAA to eeprom at run-time and read it back.
write_eeprom(10, 0xAA);
printf("Wrote 0xAA to eeprom address 10\n\r");
printf("Read %X\n\r", read_eeprom(10));
printf("\n\rDone\n\r");
while(1);
}
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ThomasC
Joined: 09 Oct 2007
Posts: 62
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| Posted: Thu Nov 15, 2007 4:38 pm |
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Thanks that example helped a lot. I was able to get the same output as you. But I do not understand the 0x55 part. What if I want to store a variable into eeprom instead of 0x55 and then read and display that?
I tried my variable called "CurrentTemp" Which is about -255.05, and it prints the value read 86. Many thanks. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Nov 15, 2007 4:53 pm |
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Here is a demo program that shows how to save floats in internal eeprom.
The code is based on this CCS FAQ article:
http://www.ccsinfo.com/faq.php?page=write_eeprom_not_byte
| Code: |
#include <16F690.h>
#fuses INTRC_IO, NOWDT, BROWNOUT, PUT, MCLR
#use delay(clock=8000000)
#use rs232(baud=9600, xmit=PIN_B7, rcv=PIN_B5, ERRORS)
void write_float_to_eeprom(int8 addr, float data)
{
int8 i;
for(i = 0; i < 4; i++)
write_eeprom(addr + i, *((int8*)&data + i) ) ;
}
//--------------------------------------
float read_float_from_eeprom(int8 addr)
{
int8 i;
float data;
for(i = 0; i < 4; i++)
*((int8*)&data + i) = read_eeprom(addr + i);
return(data);
}
//==========================
main()
{
float value1, value2, value3, result;
value1 = 1.234;
value2 = -4.567;
value3 = 567.89;
// Write the float values to internal eeprom.
// Floats take 4 bytes, so the eeprom addresses must
// be spaced 4 bytes apart, as shown below.
write_float_to_eeprom(0, value1);
write_float_to_eeprom(4, value2);
write_float_to_eeprom(8, value3);
// Read the floats from eeprom and display them.
result = read_float_from_eeprom(0);
printf("Addr 0: result = %7.3f \n\r", result);
result = read_float_from_eeprom(4);
printf("Addr 4: result = %7.3f \n\r", result);
result = read_float_from_eeprom(8);
printf("Addr 8: result = %7.3f \n\r", result);
while(1);
}
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ThomasC
Joined: 09 Oct 2007
Posts: 62
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| Posted: Fri Nov 16, 2007 9:35 am |
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Thank you man. It works!  |
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