I2c EEPROM Read byte - Electronic Circuits Projects Diagrams Free

FarshadN · 1st November 2009, 12:51 PM

Hi all,

I've used a PIC16f876a and could successfully write 128Byte (as LCD CHR codes) into 24C512 Eeprom, the problem rose when I try to read bytes back and display onto LCD.

when doing random read I can successfully read one byte from any where in the memory page, but after the first byte when i send ACK to read more, all i get is 0xff on all byte and LCD shows █. no matter what.

I'd appreciate any help.

Farshad

Sceadwian · 1st November 2009, 01:01 PM

Are you sure you're using the right command to read the next byte?

Pommie · 1st November 2009, 01:55 PM

Post your code. You must be doing something wrong but I can't think what it might be.

Mike.

FarshadN · 4th November 2009, 11:52 AM

here is my code:
as I mentioned the first read is fine but when it goes to the loop for next bytes it's wrong data display on LCD.

setup

bcf STATUS, RP0
clrf PORTB
clrf PORTC
bsf STATUS, RP0 ;bank1
movlw b'00011100'
movwf TRISC ; PORTC <4:3> as input
bcf STATUS, RP0 ;bank0

call INITLCD

clrf SSPCON
movlw b'00101000' ;init I2C with FOsc
movwf SSPCON

bcf PIR1, SSPIF ;init XT flag bit

bsf STATUS, RP0 ;bank1
clrf SSPCON2 ;init SSPCON2
clrf SSPSTAT
bsf SSPSTAT, SMP ;slew disable for 100KHz
bcf SSPSTAT, CKE ;SMBus disabled
movlw h'9'
movwf SSPADD ; 100Khz baud rate
bcf STATUS, RP0 ;bank0
movlw d'16'
movwf data_count

read_mode
bsf STATUS, RP0 ;bank1
bsf SSPCON2, SEN ; send Start
btfss SSPSTAT, S
goto $-1
bcf STATUS, RP0 ;bank0
btfss PIR1, SSPIF ;wait till Start completed
goto $-1
bcf PIR1, SSPIF ; clear TXflag bit
movlw b'10100000'
movwf SSPBUF ;set device address<0>write
bsf STATUS, RP0 ;bank1
btfsc SSPSTAT, BF ; check if buffer is empty
goto $-1
btfsc SSPCON2, ACKSTAT ; check if ACK received
goto $-1
bcf STATUS, RP0 ;bank0
btfss PIR1, SSPIF ;wait till Start completed
goto $-1
bcf PIR1, SSPIF ; clear TXflag bit
movlw d'0'
movwf SSPBUF ; first word address
bsf STATUS, RP0 ;bank1
btfsc SSPSTAT, BF ; check if buffer is empty
goto $-1
btfsc SSPCON2, ACKSTAT ; check if ACK received
goto $-1
bcf STATUS, RP0 ;bank0
btfss PIR1, SSPIF ;wait till Start completed
goto $-1
bcf PIR1, SSPIF ; clear TXflag bit
movlw d'5'
movwf SSPBUF ;second word address page0=0, page1=128
bsf STATUS, RP0 ;bank1
btfsc SSPSTAT, BF ; check if buffer is empty
goto $-1
btfsc SSPCON2, ACKSTAT ; check if ACK received
goto $-1
bcf STATUS, RP0 ;bank0
btfss PIR1, SSPIF ;wait till Start completed
goto $-1
bcf PIR1, SSPIF ; clear TXflag bit
bsf STATUS, RP0 ;bank1
bsf SSPCON2, RSEN ;send Restart
btfss SSPSTAT, S
goto $-1
bcf STATUS, RP0 ;bank0
btfss PIR1, SSPIF ;wait till Start completed
goto $-1
bcf PIR1, SSPIF ; clear TXflag bit
movlw b'10100001'
movwf SSPBUF ;set device address<1>read
bsf STATUS, RP0 ;bank1
btfsc SSPSTAT, BF ; check if buffer is empty
goto $-1
btfsc SSPCON2, ACKSTAT ; check if ACK received
goto $-1
bcf STATUS, RP0 ;bank0
btfss PIR1, SSPIF ; wait XT complete
goto $-1
bcf PIR1, SSPIF ; clear TXflag bit
data_read
bsf STATUS, RP0 ;bank1
bsf SSPCON2, RCEN ;I2C receive enabled
btfss SSPSTAT, BF ; check if buffer is full
goto $-1
bcf STATUS, RP0 ;bank0
btfss PIR1, SSPIF ;wait till Start completed
goto $-1
bcf PIR1, SSPIF ; clear TXflag bit
bcf STATUS, RP0
movf SSPBUF, w
call LCDWRITE ;data to LCD
clrf SSPBUF
bsf STATUS, RP0
bcf SSPCON2, ACKDT ;ACK send
bsf SSPCON2, ACKEN ;init Sequel ACK
bcf STATUS, RP0 ;bank0
btfss PIR1, SSPIF ;wait till Start completed
goto $-1
bcf PIR1, SSPIF ; clear TXflag bit
decfsz data_count, f
goto data_read
return

read_end
bsf STATUS, RP0 ;bank1
bsf SSPCON2, ACKDT ;NO acknowlege bit
bsf SSPCON2, ACKEN ;init Sequel ACK
bcf STATUS, RP0 ;bank0
btfss PIR1, SSPIF ;wait till Start completed
goto $-1
bcf PIR1, SSPIF ; clear TXflag bit
bsf SSPCON2, PEN ;send Stop bit
btfss SSPSTAT, P
goto $-1
bcf STATUS, RP0 ;bank0
btfss PIR1, SSPIF ; wait XT complete
goto $-1
bcf PIR1, SSPIF ; clear TXflag bit

FarshadN · 4th November 2009, 11:54 AM

Hi
please have a look at my code.
thanks!

Pommie · 4th November 2009, 12:29 PM

Too late for me now. If nobody answers before tomorrow I'll take a look.

Mike.

FarshadN · 9th November 2009, 12:06 PM

Hi Mike!

have you had time to look at my code. I also added a "btfsc SSPSTAT, R-W" check after the RCEN was set to slow down the loop, but still same problem all I get is 0xff on all bytes.

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1st November 2009, 12:51 PM	#1
FarshadN	I2c EEPROM Read byte Hi all, I've used a PIC16f876a and could successfully write 128Byte (as LCD CHR codes) into 24C512 Eeprom, the problem rose when I try to read bytes back and display onto LCD. when doing random read I can successfully read one byte from any where in the memory page, but after the first byte when i send ACK to read more, all i get is 0xff on all byte and LCD shows █. no matter what. I'd appreciate any help. Farshad

1st November 2009, 01:01 PM	#2
Sceadwian	Are you sure you're using the right command to read the next byte? __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

1st November 2009, 01:55 PM	#3
Pommie	Post your code. You must be doing something wrong but I can't think what it might be. Mike.

4th November 2009, 11:52 AM	#4
FarshadN	here is my code: as I mentioned the first read is fine but when it goes to the loop for next bytes it's wrong data display on LCD. setup bcf STATUS, RP0 clrf PORTB clrf PORTC bsf STATUS, RP0 ;bank1 movlw b'00011100' movwf TRISC ; PORTC <4:3> as input bcf STATUS, RP0 ;bank0 call INITLCD clrf SSPCON movlw b'00101000' ;init I2C with FOsc movwf SSPCON bcf PIR1, SSPIF ;init XT flag bit bsf STATUS, RP0 ;bank1 clrf SSPCON2 ;init SSPCON2 clrf SSPSTAT bsf SSPSTAT, SMP ;slew disable for 100KHz bcf SSPSTAT, CKE ;SMBus disabled movlw h'9' movwf SSPADD ; 100Khz baud rate bcf STATUS, RP0 ;bank0 movlw d'16' movwf data_count read_mode bsf STATUS, RP0 ;bank1 bsf SSPCON2, SEN ; send Start btfss SSPSTAT, S goto $-1 bcf STATUS, RP0 ;bank0 btfss PIR1, SSPIF ;wait till Start completed goto $-1 bcf PIR1, SSPIF ; clear TXflag bit movlw b'10100000' movwf SSPBUF ;set device address<0>write bsf STATUS, RP0 ;bank1 btfsc SSPSTAT, BF ; check if buffer is empty goto $-1 btfsc SSPCON2, ACKSTAT ; check if ACK received goto $-1 bcf STATUS, RP0 ;bank0 btfss PIR1, SSPIF ;wait till Start completed goto $-1 bcf PIR1, SSPIF ; clear TXflag bit movlw d'0' movwf SSPBUF ; first word address bsf STATUS, RP0 ;bank1 btfsc SSPSTAT, BF ; check if buffer is empty goto $-1 btfsc SSPCON2, ACKSTAT ; check if ACK received goto $-1 bcf STATUS, RP0 ;bank0 btfss PIR1, SSPIF ;wait till Start completed goto $-1 bcf PIR1, SSPIF ; clear TXflag bit movlw d'5' movwf SSPBUF ;second word address page0=0, page1=128 bsf STATUS, RP0 ;bank1 btfsc SSPSTAT, BF ; check if buffer is empty goto $-1 btfsc SSPCON2, ACKSTAT ; check if ACK received goto $-1 bcf STATUS, RP0 ;bank0 btfss PIR1, SSPIF ;wait till Start completed goto $-1 bcf PIR1, SSPIF ; clear TXflag bit bsf STATUS, RP0 ;bank1 bsf SSPCON2, RSEN ;send Restart btfss SSPSTAT, S goto $-1 bcf STATUS, RP0 ;bank0 btfss PIR1, SSPIF ;wait till Start completed goto $-1 bcf PIR1, SSPIF ; clear TXflag bit movlw b'10100001' movwf SSPBUF ;set device address<1>read bsf STATUS, RP0 ;bank1 btfsc SSPSTAT, BF ; check if buffer is empty goto $-1 btfsc SSPCON2, ACKSTAT ; check if ACK received goto $-1 bcf STATUS, RP0 ;bank0 btfss PIR1, SSPIF ; wait XT complete goto $-1 bcf PIR1, SSPIF ; clear TXflag bit data_read bsf STATUS, RP0 ;bank1 bsf SSPCON2, RCEN ;I2C receive enabled btfss SSPSTAT, BF ; check if buffer is full goto $-1 bcf STATUS, RP0 ;bank0 btfss PIR1, SSPIF ;wait till Start completed goto $-1 bcf PIR1, SSPIF ; clear TXflag bit bcf STATUS, RP0 movf SSPBUF, w call LCDWRITE ;data to LCD clrf SSPBUF bsf STATUS, RP0 bcf SSPCON2, ACKDT ;ACK send bsf SSPCON2, ACKEN ;init Sequel ACK bcf STATUS, RP0 ;bank0 btfss PIR1, SSPIF ;wait till Start completed goto $-1 bcf PIR1, SSPIF ; clear TXflag bit decfsz data_count, f goto data_read return read_end bsf STATUS, RP0 ;bank1 bsf SSPCON2, ACKDT ;NO acknowlege bit bsf SSPCON2, ACKEN ;init Sequel ACK bcf STATUS, RP0 ;bank0 btfss PIR1, SSPIF ;wait till Start completed goto $-1 bcf PIR1, SSPIF ; clear TXflag bit bsf SSPCON2, PEN ;send Stop bit btfss SSPSTAT, P goto $-1 bcf STATUS, RP0 ;bank0 btfss PIR1, SSPIF ; wait XT complete goto $-1 bcf PIR1, SSPIF ; clear TXflag bit Last edited by FarshadN; 9th November 2009 at 12:03 PM.

4th November 2009, 11:54 AM	#5
FarshadN	Hi please have a look at my code. thanks!

4th November 2009, 12:29 PM	#6
Pommie	Too late for me now. If nobody answers before tomorrow I'll take a look. Mike.

9th November 2009, 12:06 PM	#7
FarshadN	Hi Mike! have you had time to look at my code. I also added a "btfsc SSPSTAT, R-W" check after the RCEN was set to slow down the loop, but still same problem all I get is 0xff on all bytes. Last edited by FarshadN; 9th November 2009 at 12:06 PM.