I2CWRITE problem

[Paul]

Paul, I notice that you have only declared 31 WORDS but you are loading the eeprom with 32 BYTES. You can only load individual BYTES into the eeprom even if they are in an array. You would be loading the LOWBYTE of each of the words in the DATA array into the eeprom. Even then, you have only declared 31 words and not 32.

Dave Purola,
N8NTA

Hi Dave,

That is correct, the 1st element in the array, DATA[0], the second element DATA[1], the 32nd DATA[31].

The STR command counts the elements in an array, [ STR DATA\1] would send element DATA[0]. PBPro knows if I am using WORDS or BYTES and counts them appropriately.

In this section of the PBPro manual, it clearly states that WORD variable arrays can be sent.

Paul.

[Gusse]

Hi Dave,

That is correct, the 1st element in the array, DATA[0], the second element DATA[1], the 32nd DATA[31].

The STR command counts the elements in an array, [ STR DATA\1] would send element DATA[0]. PBPro knows if I am using WORDS or BYTES and counts them appropriately.

In this section of the PBPro manual, it clearly states that WORD variable arrays can be sent.

Paul.

Hi Paul,

Check from manual about Arrays

It is two different things:
- Number of elements (array; 1,2,3,... )
- Location of element (string; 0,1,2,... )

BR,
-Gusse-

[Art]

Just to elaborate on the problem,
The middle part of this video shows the function that writes to EEPROM.
The messages are short because I can only type about 15 letters before
the first one stuffs up.
Each letter requires 6 bytes because they are stored as mono bitmaps,
and there is some lead in space written with zeros.



Art.

[Gusse]

Hi Art,

Couple of things came to my mind:

What is your oscillator speed?
- I didn't see any DEFINE OSC parameter.

Is EEPROM only load in I2C bus?
- Capacitive loading below 400pF per signal line (I2C spec)

How long wires you have between PIC and EEPROM?
- Timing CLK & data (this should not be a problem for I2C)

Write control pin in EEPROM?
- Grounded? Don't know if floating pin could do something like this?

De-coupling of PIC and EEPROM?
- How many caps and sizes

Crosstalk
- Any nearby signals that could cause coupling?

Grounding
- How is the grounding done? Ground bounce due to common impedance with some high current part of the system (Power supply, PIC, etc...).

Errors in write mode seems to be very systematic so it can't be just noise, which is causing the problem.

BR,
-Gusse-

[Dave]

Paul, Yes I understand that the base element number starts at 0 but, you are DECLARING only 31 elements in the array and not 32. Your declaration of the array size has to be the actual number of elements NOT the last element index. RTFM..... Also think about this statement from the manual...(While a single I2CWRITE statement may be used to write multiple bytes at once, doing so may violate the above write timing requirement for serial EEPROMs. Some serial EEPROMS let you write multiple bytes into a single page before necessitating the wait. Check the data sheet for the specific device you are using for these details. The multiple byte write feature may also be useful with I2C devices other than serial EEPROMs that don=t have to wait between writes.) Thats why I always use the page mode.....

Dave Purola,
N8NTA

[Art]

DATA var WORD [31]

It's the same in any programming language.
You declare the number of elements as a Human would say it
"there are 31 elements in the array" (not correct in this case).

Man I tried everything..
2.2K resistors, even shortened the clock and data wired to about six cm each.
it's really time for a new circuit to do the same test,
but I don't know what else I could change.

[Dave]

Art, Have you tried the page write mode for storing your data? True, you need a shadow array the size of the page you are trying to write but it is much faster to write a full page than individual bytes if you have any quanity.. Try these subroutines that I wrote a long time ago for an analog waveform generator using a single 24LC512 utilizing the page mode. This routine will store 7 diferent files, made up of 64 blocks of 128 bytes each. I hope this helps...

CNTRL_BYTE CON $A0 'CONTROL BYTE FOR I2C EEPROM MEMORY (A0/A1 USED FOR CHIP SELECT)
BLOCK VAR BYTE '64 BLOCK ADDRESS BYTE
ADDRESS VAR WORD 'ADDRESS WORD FOR SERIAL EEPROM
CNTROL_BYTE VAR BYTE 'CONTROL BYTE TO SEND TO SERIAL EEPROM
STOR_DATA VAR BYTE[128]'STORAGE DATA ARRAY
FILE VAR BYTE 'FILE STORAGE NUMBER 0 to 7

'************************************************* ********************
WRITE_EEPROM512: 'WRITE TO SERIAL EEPROM
'************************************************* ********************
ADDRESS = FILE << 13 'CALCULATE 12C ADDRESS TO STORE DATA TO
ADDRESS = ADDRESS + (BLOCK << 7) 'CALCULATE 12C ADDRESS TO STORE DATA TO
CNTROL_BYTE = CNTRL_BYTE 'COPY CONTROL BYTE
CNTROL_BYTE.1 = 0' 'SET LSB OF HARDWARE ADDRESS
CNTROL_BYTE.2 = 0' 'SET MSB-1 OF HARDWARE ADDRESS
CNTROL_BYTE.3 = 0' 'SET MSB OF HARDWARE ADDRESS
I2CWRITE SDA,SCL,CNTROL_BYTE,ADDRESS,[STR STOR_DATA\128] 'SAVE DATA TO 12C
PAUSE 6 'ALLOW TIME FOR I2C WRITE ~5Ms.
BLOCK = BLOCK + 1 'INCREMENT BLOCK NUMBER
RETURN

'************************************************* ********************
READ_EEPROM512: 'READ FROM SERIAL EEPROM
'************************************************* ********************
ADDRESS = FILE << 13 'CALCULATE 12C ADDRESS TO STORE DATA TO
ADDRESS = ADDRESS + (BLOCK << 7) 'CALCULATE 12C ADDRESS TO STORE DATA TO
CNTROL_BYTE = CNTRL_BYTE 'COPY CONTROL BYTE
CNTROL_BYTE.1 = 0' 'SET LSB OF HARDWARE ADDRESS
CNTROL_BYTE.2 = 0' 'SET MSB-1 OF HARDWARE ADDRESS
CNTROL_BYTE.3 = 0' 'SET MSB OF HARDWARE ADDRESS
I2CREAD SDA,SCL,CNTROL_BYTE,ADDRESS,[STR STOR_DATA\128] 'LOAD IN ENTIRE BLOCK
RETURN

Dave Purola,
N8NTA

[Paul]

Hi Paul,

Check from manual about Arrays

It is two different things:
- Number of elements (array; 1,2,3,... )
- Location of element (string; 0,1,2,... )

BR,
-Gusse-

I had read this section of the manual sometime ago, and have obviously forgotten. Thank you Gusse, Art and Dave. It is good to be corrected and shown your error. Even with the change in array declaration, my page write I2C routine still will not work and exhibit the previously described problem. I will look at the physical aspects of the design (hardware), failing that attempt the hardware I2C routine. I have found some examples of code in the forums.

Paul

[Art]

Dave,
I can't really use page write because I only want to write 6 bytes at a time.
The code in the first post only writes zeros, but it isn't really what I want in my application... it's just a simplified code that exhibits the problem.

I'm duplicating the hardware today, so this will be interesting.

[Dave]

Art, Are you accumulating the data or just re-writing the values at the same locations? If you are accumulating the values (data logger style (appending)) then just wait till you have 64,128 or so on (eeprom page dependent) , readings stored in the shadow ram then dump them to the eeprom.

Dave Purola,
N8NTA

[Art]

That's a lot of bytes of RAM for the 16F877.
I think you get 368 bytes RAM, and PBP consumes some of that.

[Dave]

Art, Like I said, you can use a smaller eeprom like the 24LC256 or 24LC128 which has a 64 byte page write size or as small as a 24LC01B which has an 8 byte page write.

Dave Purola,
N8NTA