Storing Calibration Data - Electronic Circuits Projects Diagrams Free

Omar.M · 19th March 2007, 03:47 AM

Hello. For my line following, instead of having static values for the line and off the line sensor readings, I was thinking of having a button for the on-line reading and off line reading, so when I press each individual button: I could get the value and store it.

This way, my robot would be better in different conditions without having to reprogram every time.

I was wondering, is it possible? Can PICs store such data? Would anyone have any snippets?

Thanks a lot,
Omar

Pommie · 19th March 2007, 03:55 AM

That is exactly what the EEPROM is for.

Reading and writing EEPROM varies from chip to chip. Which Pic are you using?

Mike.
P.S. I think Nigel has a tutorial on this for the 16f628.

Pommie · 19th March 2007, 03:56 AM

Also, the data sheet contains example code for reading and writing.

Mike.

gramo · 19th March 2007, 07:04 AM

Here’s an example of interfacing with 4 EEPROM’s on an I2C network;

Code:

Device = 16F876
XTAL 20

ALL_DIGITAL = True
Declare SCL_PIN PORTB.0
Declare SDA_PIN PORTB.1

    

Dim TX As PORTB.2

Dim DATA_OUT As Byte
Dim DATA_IN(20) As Byte

Dim Address As Word ' 16-bit address required

For Address = 1 To 20

     DATA_OUT = Address
     BStart                                                             ' Send the start command on I2C
     BusOut %10100010,Address,[DATA_OUT]        ' Send the byte to the EEPROM
     BStop                                                            ' Send the stop command on I2C
     DelayMS 5                                                      ' Allow time for allocation of byte

Next Address

For Address = 1 To 20
    
     BStart                                                             ' Send the start command on I2C
     BusOut %10100010,[Address]                          ' Send the address to read
     Brestart                                                          ' Send a restart command on I2C
     BusIn %10100011, [DATA_IN[Address]]            ' Grab data at the above address
     BStop                                                             ' Send the stop command on I2C

Next Address

Stop

Of course you could just use one big EEPROM, but I wanted to kill 2 birds with one stone and describe I2C in my model.

http://users.tpg.com.au/gramo/Site/eeproms.htm

Pommie · 19th March 2007, 07:12 AM

Why complicate things? The OP wanted to know how to store 2 bytes. This can easily be done in the internal EEPROM of most Pic chips. Did you not realise that Pic's have internal EEPROM?

Mike.

gramo · 19th March 2007, 07:51 AM

I miss read that, sorry. In that case, just use the PIC's onboard memory as suggested;

Quote:

EWRITE 00, [Piece_Of_Data1]
EWRITE 01, [Piece_Of_Data2]

Quote:

Variable1 = EREAD 00
Variable2 = EREAD 01

Even easier

Omar.M · 19th March 2007, 01:09 PM

That simple, huh?
Thanks so much.

I should have been more clear-- I am using a 16f684 microcontroller.
Just one more question-- which address would I write the data to?

-Omar

Pommie · 19th March 2007, 01:17 PM

It's only that simple if you are using basic. If you are using assembler then copy the routines out of the data sheet - there still pretty simple. You can write to any of the locations from zero to however many bytes of EEPROM are available - 256 in the 684.

Mike.

Omar.M · 19th March 2007, 01:25 PM

Wow, that seems easy enough, thank you

And as for basic, in fact I am using BASIC!
Great Cow Basic, to be exact.
http://gcbasic.sourceforge.net/

Thanks a lot,
Omar

Oznog · 19th March 2007, 09:57 PM

Note that EEPROM has a limited write endurance. It's unlikely you would ever run into endurance problems with user-entered button presses, however for other cases where you may write them more often the write endurance can be a real issue which may limit the lifespan of the product.

gramo · 20th March 2007, 07:28 AM

This is about 1,000,000 writes, less in some cases

Omar.M · 20th March 2007, 01:32 PM

Oh. Well, I do not think I will exceed that limit-- this is merely me just experimenting with robotics; it isn't going to be in competitions or anything.

I just have a few questions. Does the data which I store in the EEPROM get erased when I power off the PIC? Or is it permanent? Is it better to get a few sensor readings and finding the average between them... or just two basic readings ?

Thanks,
Omar

**Nigel Goodwin** · 20th March 2007, 01:44 PM

The EEPROM retains the data when the power is removed. Averaging readings really depends what they are, and what you're trying to do with them.

Pommie · 20th March 2007, 01:45 PM

Whatever you put in the EEPROM should stay there for at least 40 years if you believe the data sheet.
I would average a few readings and store that. End of the day you are going to compare against the average of the 2 readings. The actual readings are probably not too important.

Mike.

Hero999 · 21st March 2007, 05:48 PM

There's normally a limit to the number of write cycles though.

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19th March 2007, 03:47 AM	(permalink)
Omar.M	Storing Calibration Data Hello. For my line following, instead of having static values for the line and off the line sensor readings, I was thinking of having a button for the on-line reading and off line reading, so when I press each individual button: I could get the value and store it. This way, my robot would be better in different conditions without having to reprogram every time. I was wondering, is it possible? Can PICs store such data? Would anyone have any snippets? Thanks a lot, Omar

19th March 2007, 03:55 AM	(permalink)
Pommie	That is exactly what the EEPROM is for. Reading and writing EEPROM varies from chip to chip. Which Pic are you using? Mike. P.S. I think Nigel has a tutorial on this for the 16f628.

19th March 2007, 03:56 AM	(permalink)
Pommie	Also, the data sheet contains example code for reading and writing. Mike.

19th March 2007, 07:12 AM	(permalink)
Pommie	Why complicate things? The OP wanted to know how to store 2 bytes. This can easily be done in the internal EEPROM of most Pic chips. Did you not realise that Pic's have internal EEPROM? Mike.

19th March 2007, 01:09 PM	(permalink)
Omar.M	Wow That simple, huh? Thanks so much. I should have been more clear-- I am using a 16f684 microcontroller. Just one more question-- which address would I write the data to? -Omar

19th March 2007, 01:17 PM	(permalink)
Pommie	It's only that simple if you are using basic. If you are using assembler then copy the routines out of the data sheet - there still pretty simple. You can write to any of the locations from zero to however many bytes of EEPROM are available - 256 in the 684. Mike.

19th March 2007, 01:25 PM	(permalink)
Omar.M	Wow, that seems easy enough, thank you And as for basic, in fact I am using BASIC! Great Cow Basic, to be exact. http://gcbasic.sourceforge.net/ Thanks a lot, Omar

19th March 2007, 09:57 PM	(permalink)
Oznog	Note that EEPROM has a limited write endurance. It's unlikely you would ever run into endurance problems with user-entered button presses, however for other cases where you may write them more often the write endurance can be a real issue which may limit the lifespan of the product. __________________ I thought what I'd do was I'd pretend I was one of those deaf-mutes.

20th March 2007, 07:28 AM	(permalink)
gramo	This is about 1,000,000 writes, less in some cases __________________ Spency. PIC Micro's - Your mind is the limit PIC's and interfacing with other devices - a PIC Basic Guide @ digital-diy.net

20th March 2007, 01:32 PM	(permalink)
Omar.M	Oh Oh. Well, I do not think I will exceed that limit-- this is merely me just experimenting with robotics; it isn't going to be in competitions or anything. I just have a few questions. Does the data which I store in the EEPROM get erased when I power off the PIC? Or is it permanent? Is it better to get a few sensor readings and finding the average between them... or just two basic readings ? Thanks, Omar

21st March 2007, 05:48 PM	(permalink)
Hero999	There's normally a limit to the number of write cycles though. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

20th March 2007, 01:44 PM	(permalink)
Nigel Goodwin	The EEPROM retains the data when the power is removed. Averaging readings really depends what they are, and what you're trying to do with them. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

20th March 2007, 01:45 PM	(permalink)
Pommie	Whatever you put in the EEPROM should stay there for at least 40 years if you believe the data sheet. I would average a few readings and store that. End of the day you are going to compare against the average of the 2 readings. The actual readings are probably not too important. Mike.