I2C and 24LC65

[Archangel]

Hello afbecker,
Here is an example which might be helpful:

' I2CREAD and I2WRITE Commands with External EEPROM on 12-bit core
'
' Write to the first 36 locations of External I2C EEPROM
' Read from eeprom and output sequentaly then as strings
' Tested on 12F675  using 24LC01B EEPROM
@ __config _INTRC_OSC_NOCLKOUT & _PWRTE_ON & _WDT_ON & _MCLRE_ON & _CP_OFF & _BODEN_OFF
DEFINE OSC 4
 
DEFINE DEBUG_REG	GPIO
DEFINE DEBUG_BIT	2
DEFINE DEBUGIN_BIT	5
DEFINE DEBUG_BAUD	2400
DEFINE DEBUG_MODE	0
DEFINE SHIFT_PAUSEUS 1000

EECON1   = 7  'Probably not needed here, enables internal eeprom
CMCON    = 7  'Disable comparators
ADCON0.0 = 0  'Disable A/D converters
ANSEL    = 0  'Disables Analog Select
DPIN var GPIO.0   'Assign Data pin
CPIN var GPIO.1   'Assign Clock pin
            ' a nice place to store things
B0 var byte
B1 var byte
B2 var byte
B3 VAR BYTE

GPIO   = 0 ' set port latches low
TRISIO = 0 ' set ports as outputs

pause 1000 ' Waste time while serial LCD initiailizes

For B2 = 0 To 35   ' counter for lookup table
lookup b2,["A","B","C","D","E","F","G","H","I","J","K","L","M",_
"N","O","P","Q","R","S","T","U","V","W","X","Y","Z","0","1","2",_
"3","4","5","6","7","8","9"],B0 ' store each char in b0 1 at a time

I2CWRITE DPIN,CPIN,$A0,B2,[ b0]  'write to 24C01 eeprom 1 character
Pause 20
Next B2       'next character write to eeprom
DEBUG 254,1   'clear LCD of any leftover data
loop:
DEBUG 254,1   'clears away the leftovers each loop

For B3 = 0 To 35   ' counter for reading 35 characters
I2CREAD DPIN,CPIN,$A0,b3,[B1]  ' read each character 1 at a time
pause 500           ' time to see each character on the LCD


DEBUG 254,2,"CHAR ",B1,"          " ' display the characters 1 at a time
'
Next B3                             ' get next character

I2CREAD DPIN,CPIN,$A0,0,[STR B1\20] ' read a string of  20 characters
DEBUG 254,2,STR B1\20               ' display those 20 characters
I2CREAD DPIN,CPIN,$A0,16,[STR B1\16]' get the last 16 characters
DEBUG 254,$C0,STR B1\16,"    "      ' display those 16 characters
DEBUG 254,$94,"I2C EEPROM DEMO"     ' display this program's purpose
DEBUG 254,$D4,"USING ARRAY & STRING" 
PAUSE 1500                          ' time to read the LCD
'NEXT B3                            ' go do it all again
Goto loop
end
POKECODE @$3FF, $4C  'read your PIC before erasing and put the cal. data here

[afbecker]

Gentlemen,

Thanks for the quick reply, I can work on this tonight!

Aratti: For my future reference, can you tell me what the difference is between the control bytes, particularily the read control byte ending in 1? I wondered if that was the key to making my specific part work.

Joe S.: I appreciate the code example. Reading example code is a way I find that I can learn new concepts very easily.

[aratti]

I wondered if that was the key to making my specific part work.

Although in this forum, I have read in several posts that I2CRead set the LSB to 1 automatically, I have never been able to read successfully, from external memory, without setting LSB to 1 myself. Now I do it as a standard in all my codes using I2C commands.

Al.

[Bill Legge]

I think your problem is with the address for READ and WRITE.

The 24LC64 EEPROM needs a WORD size address - even if the actual address is 0.

Change your program to

DEFINE B0 WORD ; Must not be a BYTE size or CONSTANT

B0 = 0
I2CWRITE, DataPin,ClockPin,$A0,B0,[Value]

and so on....

Good luck. I stuffed around with EEPROM for ages and eventualy found that all my errors were due to using BYTES when the chips expected a WORD. The spec sheet for the chip will tell you what it expects. The example in the PBP book is for a smaller EEPROM that only needs a BYTE address.

Regards Bill Legge

[afbecker]

Bill,

You are absolutely correct.

It came to me last night in a flash (pun intended.) I was re-reading the docs. and I realized I had defined the address variable as a byte type and the address of this part is a word type.

After I had changed it everything works superbly!

As a quick reply to Arratti: I am embarassed that I asked the question about the control word difference. At the time I replied I hadn't looked at the EPROM docs. for about two weeks. I forgot the difference in control words was due to the read/write mode.

Rhetorical question: Isn't it amazing how elementary a problem suddenly becomes once you have figured out the solution?