I2CWRITE problem

[Art]

Hi Guys,
I seem to be able to READ ok with I2CREAD,
but I'm having difficulty with my program, and I've narrowed it down to I2CWRITE.

I'm using a 24LC512 EEPROM, and I've also tried 256.

W0 var byte
epin var word

W0 = 0
FOR cntr = 0 TO 2000					'
I2CWRITE porte.1,porte.2,%10100000,epin,[W0,W0,W0,W0,W0],error	'
pause 10						'
epin = epin + 5						'
NEXT cntr						'

It would seem this code should write a lot of zeros, but when I read back the chip
there are some missing.
I have erased the EEPROM with my programmer which sets all $FF values,
and then run this code, then I find when I read back the EEPROM with my
pic programmer (or with picbasic code) there are some zero bytes.

They appear to be in groups of 2 or 3 bytes at addresses like:
100h, 180h, 200h, 280h, 300h, 380h, and so on.

Any ideas on this? Anyone else seen the same problem?

I'm using a 16F877A and Port e 1&2 to do the I2C stuff.
Art.

[Art]

Oh, I should add that I can entirely write and verify both EEPROMs properly with my pic programmer.

[Dave]

Art, Do you have any interrupts going on in the program? I have seen in the past that if you are interrupted during a I2CWRITE to some eeproms you will write bad data to the locations...

Dave Purola,
N8NTA

[mackrackit]

Just a couple of things to check/try...

Check:
ADC turned off for E.1 and E.2

Try:
DEFINE I2C_SLOW

[Art]

ADC turned off for E.1 and E.2

Try:
DEFINE I2C_SLOW

Yep, I have all digital pins. The EEPROM works most of the time,
it just doesn't want to write some addresses.
DEFINE I2C_SLOW 1 made no difference.

No interrupts in this program either.

4.7K pullups, checked 5 Volt supply.

[Gusse]

Hi Art & All,

Thanks to Art, I noticed similar I2CWRITE problem with different PIC and EEPROM (I use 18F4520 and 24C64).
So far I haven't use external EEPROM for storing anything, just used I2CREAD and that has worked very well.

Below is my test code for WRITE/READ for EEPROM. Test will be passed if X=0 (LED blinking slowly), if X > 0 then it fails immediately (LED blinking fast).

<code><font color="#000000">OSCCON = $70                <font color="#000080"><i>'Int CLK 8MHz
</i></font>OSCTUNE.6 = 1               <font color="#000080"><i>'PLL 4x
</i></font>ADCON1= %00001111           <font color="#000080"><i>'$0F = disable A/D converter
</i></font>TRISD.0 = 0
TRISD.1 = 1
TRISD.3 = 0
TRISE.4 = 0

<b>DEFINE </b>OSC 32

X       <b>VAR BYTE
</b>Y       <b>VAR BYTE
</b>SCL     <b>VAR </b>PortD.0 
SDA     <b>VAR </b>PortD.1   
LED     <b>VAR </b>PortD.3

I2CDeviceEEprom     <b>VAR BYTE   
</b>I2CAddressEEprom    <b>VAR WORD 
</b>I2CDeviceEEprom=$A0

X=0    <font color="#000080"><i>'OK if EEPROM content is 00h and X = 0, if X &gt; 0 then fails

</i></font><b>FOR </b>I2CAddressEEprom = 0 <b>TO </b>8191
    <b>I2CWRITE </b>SDA, SCL, I2CDeviceEEprom, I2CAddressEEprom,[ X ], Error			
    <b>PAUSE </b>10
    <b>I2CREAD </b>SDA, SCL, I2CDeviceEEprom, I2CAddressEEprom,[ Y ], Error
    <b>IF </b>Y &lt;&gt; X <b>THEN GOTO </b>Error
<b>NEXT </b>I2CAddressEEprom

Blink:
<b>HIGH </b>LED
<b>PAUSE </b>1000
<b>LOW </b>LED
<b>PAUSE </b>1000
<b>GOTO </b>Blink

Error:
<b>HIGH </b>LED
<b>PAUSE </b>200
<b>LOW </b>LED
<b>PAUSE </b>200
<b>GOTO </b>error

<b>END</b>	
</code>

No help from DEFINE I2C_SLOW or any other that I have tried so far (increasing PAUSE time between write and read, etc...).
Hardware is OK, because I have used it for other purpose and then PIC read only from EEPROM (same PIC and EEPROM). Pull-ups are 4.7k and very solid 5V (no dips). Data lines are quite short (~25mm). EEPROM is only device in I2C-bus. WP pin is grounded....
Sounds very similar problems as Art has.

BR,
-Gusse-

[Archangel]

Hi Gusse,
Your code does not loop, I am sitting here wondering if there is some latency in your hardware, causing your code to run ahead of the eeprom, so the code is finished before the eeprom has finished waking up . . . Maybe in Art's too . . BTW ART, I liked your talking clock, esp when it encounters an error