PIC16F690 - 24LC08B: they won't talk...

[xnihilo]

Hello,

I'm p....d off right now.
I'm using a PIC16F690.
I'm trying to store and read back 1 databyte to a 24LC08B EEPROM.
I connected the EEPROM accroding to the schematics found in PBP manual (I2C section).
It does not seem to work.
I've checked to see if I had VDD and VSS at eeprom pins, alright, I use 4.7k WPU; alright.
I don't see what can be wrong. I paste snippets related to this code section.

What's funny is that when I display the value of the value read after the write I get "0" which is not the initial value of the variable before the write. It means it can read (assuming the read walue is "0" but it cannot write (= write value '33' at first position in EEPROM... Why?

Could someone have a look?

Variable declaration:

ep_address VAR BYTE
eep_control VAR BYTE

checkwrite var BYTE         'used to check external EEPROM (in mag) operations

Registers setting

OSCCON = %01110001	'int osc, hs, 8mhz
''''''CMCON0 =  %00000111			'comparators OFF, val = 7

CM1CON0.7 = 0           'comparator1 disabled
CM2CON0.7 = 0           'comparator2 disabled

ANSEL = %00000000			'choose digital i/o, val = 0
OPTION_REG = %01111111 			'enable internal porta weak pullups resistors (no weak pull-up available for porta.3), p12. they bring pin to High state; to set a change, pull pin to ground


'First PORT then TRIS, see Mid-range MCU DS !!!

TRISA = %011011 	'a5 is output (to lcd pins), A4 is input from supplier (score request)
TRISC = %00000000
TRISB = %0000

WPUA =  %000111 			'enable weak pull ups individually on portA
'Rem: porta.3 (MCLR) has no internal weak pullups, we add an external 10k WPU !!!!
'100k wpd on A4
WPUB = %0000


PORTA = %001111 			'set pins logic
PORTB = %0000
PORTC = %00000000 			'set pins logic
'porta pins with weak pullups will be set to high (i.e. 5v by the pullups)

Variables initialization

eep_address = 0
eep_control = %10100000 'block 0 (of 0-3), byte 0 (of 0 to 255)

The code section writing and checking EEPROM

    'routine that checks if the external eeprom (the mag) is connected to the supplier
    'it writes than reads back the test value (33)
    checkwrite = 33
    eep_address = 0     'use storage byte 1 of 255 fo rthe test
    I2CWRITE PORTC.6,PORTC.7,eep_control,eep_address,[checkwrite]    'store maxitem value in the mag external EEPROM
    PAUSE 15        'hadware dependent
    I2CREAD PORTC.6,PORTC.7,eep_control,eep_address,[checkwrite]    'store maxitem value in the mag external EEPROM
    LCDOUT $fe,1,"I2C:",#checkwrite
    PAUSE 2000
    IF (checkwrite != 33) then
        LCDOUT $fe,1,"couldn't write"
        PAUSE 4000
        checkwrite = 0
        GOTO endofroutine
    ENDIF
    checkwrite = 66