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

**mackrackit** · - 18th April 2010, 00:51

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** · - 18th April 2010, 01:21

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** · - 18th April 2010, 22:59

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...

Code:

 
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** · - 19th April 2010, 11:40

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** · - 19th April 2010, 19:10

Originally Posted by Dave

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???

Code:

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???

**mackrackit** · - 19th April 2010, 21:23

10100000
Is the R/W bit. Leave it as "0" and PBP takes care of parsing it to a "1" if needed.

10100000
Are the A0 and A1 bits. If pins A0 and A1 are connected to the zero rail leave as zero. Mixing and matching on or the other or both gives the four combination's for up to four chips on the same bus.

10100000
Is the bit to set to read or write to the first or second block.

**mackrackit** · - 19th April 2010, 21:59

Here is how to read and write to a Serial EEPROM using SHIFTIN/SHIFTOUT.
Using a 24FC1025.

Why???? Why not???

I have the DATA and CLOCK pins pulled up with 2.7k resistors.
Follow the code with the data sheet to understand what is going on.

Code:

DEFINE OSC 20

DPIN    VAR PORTB.2    'I2C DATA PIN
CPIN    VAR PORTB.1    'I2C CLOCK PIN
CONT1   CON %10100001  'READ CONTROL
CONT0   CON %10100000  'WRITE CONTROL
ADDR_HB   VAR BYTE
ADDR_LB    VAR BYTE
DATOW       VAR BYTE
ACK            VAR BIT
ADDR_HB = 0'%00000000
ADDR_LB = 0'%00000000
DATOW    VAR BYTE
CNT VAR BYTE
CNT = 0

START:
    CNT = CNT + 1
    DATOW = 245
    GOSUB WRITE_DATA
    PAUSE 10
    GOSUB READ_DATA
    LCDOUT $FE,1,"TEST ",DEC CNT
    lcdout $FE,$C0,"DATA IN ",DEC DATI
    lcdout $FE,$90,"LB ",DEC ADDR_LB
    PAUSE 250
    GOTO START
    
    WRITE_DATA:     
    ADDR_LB = ADDR_LB + 1
    GOSUB START_ROM
    SHIFTOUT DPIN,CPIN,1,[CONT0]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTOUT DPIN,CPIN,1,[ADDR_HB]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTOUT DPIN,CPIN,1,[ADDR_LB]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTOUT DPIN,CPIN,1,[DATOW\8]      
    SHIFTOUT DPIN,CPIN,1,[%1\1]
    GOSUB STOP_ROM
    PAUSE 10
    RETURN
    
    READ_DATA: 
    GOSUB START_ROM
    SHIFTOUT DPIN,CPIN,1,[CONT0]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTOUT DPIN,CPIN,1,[ADDR_HB]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTOUT DPIN,CPIN,1,[ADDR_LB]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    GOSUB START_ROM
    SHIFTOUT DPIN,CPIN,1,[CONT1]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTIN DPIN,CPIN,0,[DATI\8]
    SHIFTOUT DPIN,CPIN,1,[%1\1]
    GOSUB STOP_ROM
    PAUSE 10
    RETURN
    
    START_ROM:
    HIGH CPIN:HIGH DPIN:LOW DPIN:RETURN
    STOP_ROM:
    HIGH CPIN:LOW DPIN:HIGH DPIN:RETURN

Make sure you have ANALOG turned off!!

**wolwil** · - 20th April 2010, 02:47

Thanks for the code guys! I will try it out on sunday when I get back.

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

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Changed the Pullups to 2.2K and still no change

Just for fun...

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