How to read & write to a 25aa1024 (1 Mbit SPI Bus Serial EEPROM) via 16F88

[wolwil]

How do you have pins A0 and A1 connected?

I have not had a chance to work on this today yet so I do not have any new news.

Tied to ground.

[Dave]

mackrackit, You can't use Shiftout and Shiftin for an I2C bus driven part. That is why you had no luck using it with a 24FC1025... It requires the pullup resistor for communicating the ACK signal back to the processor. Shiftout keeps the pin in an active state wghich ever it is... I recently posted code for talking to 24LC1025's here on the forum... Why not just use it for a starting point... I don't remember which thread it was in reply to but I believe it had to do with I2C....

Dave Purola,
N8NTA

[wolwil]

Dave,

I've searched through all the posts on the 24LC1025 and didn't find any code you posted but I found code that is basically the same as what I have tried already. If you can find the thread you were thinking of that would be great.

The only thing I have not tried is changing is my pullups from 4.7k to 2k and trying to write to it 1 page at a time but if I cant byte-write to begin with I'm sure the page write will not work either. I will try changing the Pullups tonight and see what happens.

[mackrackit]

I got the idea for shifting here.
http://www.rentron.com/PicBasic/i2c_communication.htm

Reading back over my code and data sheet I see some things are backwards. Maybe ...

Never did find that code posting. Found lots of others for different parts.

[wolwil]

Everything is the same as before with the new pullup values of 2.2K...back to the drawing board

I am going to be out of town for the next week so I wont be able to test anything new but I will be on here checking if any new ideas/breakthroughs come up.

[Dave]

wolwil, Here it is again incase you didn't find it. Maxpages is set for 1023 x the number of 24LC1025's you have connected. The routine saves the last storage pointer in the last 2 locations of the last 24LC1025. Block is incremented once for each page. Before you start a clean write you would set block to 0 which is the first page. When you want to read back the data then you would call READ_WRITE_BLK1025 and block would have the last address written..

This routine is rock solid and I use it for accessing 4 x 24LC1025's for a total of over 4 gigabits of memoy to record Azmnuth,Elevation,East/West/Up/Down Sensor data and control flag information for about 2 months at 1 minute intervals... I hope this helps...

 
CNTRL_BYTE    CON    $A0        'CONTROL BYTE FOR 24LC1025 I2C EEPROM MEMORY (A0/A1 USED FOR CHIP SELECT)
MAX_PAGES    CON    4095    'MAXIMUM MEMORY STORAGE PAGES,(32 BYTES/MINUTE x 4 MINUTES x PAGES = TOTAL MINUTES)
 
'*********************************************************************
RW_EEPROM1025:        'READ FROM or WRITE TO SERIAL EEPROM
'*********************************************************************
    IF READ_WRITE = 1 THEN    'WRITE 128 BYTE BLOCK TO EEPROM
        IF BLOCK <> 0 THEN    'IF STARTING NEW PASS DON'T READ OLD LOCATION
            READ_WRITE = 0    'SET FOR BLOCK READ
            GOSUB READ_WRITE_BLK1025    'READ FROM SERIAL EEPROM NEXT AVAILABLE STORAGE BLOCK
            READ_WRITE = 1    'SET FOR BLOCK WRITE
        ENDIF
        DEVICE = BLOCK / 512    'SELECT WHICH PHYSICAL ADDRESS BOUNDRY & EEPROM
        ADDRESS = BLOCK << 7    'CALCULATE 12C ADDRESS TO STORE DATA TO
        CNTROL_BYTE = CNTRL_BYTE    'COPY CONTROL BYTE
        CNTROL_BYTE.1 = DEVICE.1    'SET LSB OF HARDWARE ADDRESS
        CNTROL_BYTE.2 = DEVICE.2    'SET MSB OF HARDWARE ADDRESS
        CNTROL_BYTE.3 = DEVICE.0    'SET 64K BLOCK BIT
        INTCON.7 = 0    'CLEAR GLOBAL INTERRUPT
        I2CWRITE SDA,SCL,CNTROL_BYTE,ADDRESS,[STR STOR_DATA\128]    'SAVE DATA TO 12C
        WRITEOCCURED = 1
        INTCON.7 = 1    'SET GLOBAL INTERRUPT
        PAUSE 6        'ALLOW TIME FOR I2C WRITE ~5Ms.
        BLOCK = BLOCK + 1    'INCREMENT FOR NEXT AVAILABLE BLOCK TO WRITE
        BLOCK = BLOCK MIN MAX_PAGES    'LIMIT TO n BLOCKS OF 128 BYTES
        GOSUB READ_WRITE_BLK1025    'WRITE TO or READ FROM SERIAL EEPROM LAST STORAGE BLOCK
    ELSE
        DEVICE = BLOCK / 512    'SELECT WHICH PHYSICAL ADDRESS BOUNDRY & EEPROM
        ADDRESS = BLOCK << 7    'CALCULATE 12C ADDRESS TO STORE DATA TO
        CNTROL_BYTE = CNTRL_BYTE    'COPY CONTROL BYTE
        CNTROL_BYTE.1 = DEVICE.1    'SET LSB OF HARDWARE ADDRESS
        CNTROL_BYTE.2 = DEVICE.2    'SET MSB OF HARDWARE ADDRESS
        CNTROL_BYTE.3 = DEVICE.0    'SET 64K BLOCK BIT
        INTCON.7 = 0    'CLEAR GLOBAL INTERRUPT
        I2CREAD SDA,SCL,CNTROL_BYTE,ADDRESS,[STR READ_DATA\128]    'LOAD IN ENTIRE BLOCK
        WRITEOCCURED = 1
        INTCON.7 = 1    'SET GLOBAL INTERRUPT
    ENDIF
    RETURN
 
'*********************************************************************
READ_WRITE_BLK1025:    'WRITE TO or READ FROM SERIAL EEPROM NEXT AVAILABLE STORAGE BLOCK
'*********************************************************************
    ADDRESS = 65534        'POINT TO LAST STORED DATA(WORD) ADDRESS
    DEVICE = MAX_PAGES / 512    'SELECT WHICH PHYSICAL ADDRESS BOUNDRY & EEPROM
    CNTROL_BYTE = CNTRL_BYTE    'COPY CONTROL BYTE
    CNTROL_BYTE.1 = DEVICE.1    'SET LSB OF HARDWARE ADDRESS
    CNTROL_BYTE.2 = DEVICE.2    'SET MSB OF HARDWARE ADDRESS
    CNTROL_BYTE.3 = DEVICE.0    'SET 64K BLOCK BIT
    IF READ_WRITE = 1 THEN
        INTCON.7 = 0    'CLEAR GLOBAL INTERRUPT
        I2CWRITE SDA,SCL,CNTROL_BYTE,ADDRESS,[BLOCK.LOWBYTE,BLOCK.HIGHBYTE]    'WRITE DATA POINTER TO 12C    
        WRITEOCCURED = 1
        INTCON.7 = 1    'SET GLOBAL INTERRUPT
        PAUSE 6        'ALLOW TIME FOR I2C WRITE ~5Ms.
    ELSE
        INTCON.7 = 0    'CLEAR GLOBAL INTERRUPT
        I2CREAD SDA,SCL,CNTROL_BYTE,ADDRESS,[BLOCK.LOWBYTE,BLOCK.HIGHBYTE]    'READ DATA POINTER FROM 12C    
        WRITEOCCURED = 1
        INTCON.7 = 1    'SET GLOBAL INTERRUPT
    ENDIF
    RETURN

Dave Purola,
N8NTA

[mackrackit]

Hi Dave,
Thanks for posting your code. I also found my problem...

My problem is "I am a newbe!!!".
I forgot PORTF.6 on the 18F6680 is an analog pin.
RTFD RTFD RTFD

For what it is worth.. When I take care of the analog issue I can read the part with SHIFTIN/OUT. I can not write to the part that way yet. Still have a timing problem I guess. It may not be worth messing with other than an exercise in coding.

[wolwil]

CNTRL_BYTE CON $A0 'CONTROL BYTE FOR 24LC1025 I2C EEPROM MEMORY (A0/A1 USED FOR CHIP SELECT)

Maybe this is where I am getting confused... you have the control byte being $A0 which is basically saying to write to the 24LC1025 seeing how the read write bit in that is a 0 like this "10100000" but the you say in your comment that the A0/A1 is for chip select...So in this following line of code where I have the $A0 is that the 8 bit control byte or just the Chip Select portion of it???

I2CREAD PORTB.1,PORTB.4,$A0,addr,[B1]

See I thought if I wanted to write to chip select A1 I needed to use $A2 or in binary like this %10100010 and if I wanted to read from it I needed to use $A3 or in binary like this %10100011.

Every combination to read and write to all 4 Chips:

%10100000 or $A0 = Write to A0 (Pins A0 & A1 Tied Low)
%10100001 or $A1 = Read from A0
%10100010 or $A2 = Write to A1 (Pins A0 Tied Low & A1 Tied High)
%10100011 or $A3 = Read from A1
%10100100 or $A4 = Write to A2 (Pins A0 Tied High & A1 Tied Low)
%10100101 or $A5 = Read from A2
%10100110 or $A6 = Write to A3 (Pins A0 and A1 Tied High)
%10100111 or $A7 = Read from A3

So with me having both A0 and A1 Pins Tied to ground I should be using the first 2 options when trying to read/write to the chip or am I just way off on this???

Am I incorrect in my thinking of what PBP is calling the Control Byte???