I2C with External Eeprom

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  1. - 19th February 2008, 20:34 #1
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    Default I2C with External Eeprom

    Hi all,

    The reason for this post is that i'm trying to get my 24LC512 eeprom to work with my PIC16F88.

    I was successful with this eeprom and a PIC12F675, but for some reason with the 16F88 i cant read nor write anything.

    I've search the forum for an answer but nothing worked.

    I've read the pic16F88 datasheet over and over and i came up with some doubts.

    Please try to answer my questions so i can proceed in finding a solution

    According to the pic 16F88's datasheet ( I2C )Pin RB1 is for SDA and pin RB4 is for SCL.

    1st question:
    Is it mandatory that i use these ports to communicate with the eeprom ?
    ( this may be a silly question but for 12F675 i can use almost any pin for them ).

    In the datasheet i have found that we need to clear SSPEN bit and program the 2 I2C ports as inputs.

    2nd question:
    For that to happen i need to mess with the SSPSTAT and SSPCON ?
    If yes, can you please show me how can these be set ( since i dont understand the meaning of their bits )

    thanks
  2. - 19th February 2008, 21:11 #2
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    Quote Originally Posted by ruijc View Post
    Hi all,
    The reason for this post is that i'm trying to get my 24LC512 eeprom to work with my PIC16F88.
    I was successful with this eeprom and a PIC12F675, but for some reason with the 16F88 i cant read nor write anything.
    I've search the forum for an answer but nothing worked.
    I've read the pic16F88 datasheet over and over and i came up with some doubts.
    Please try to answer my questions so i can proceed in finding a solution
    According to the pic 16F88's datasheet ( I2C )Pin RB1 is for SDA and pin RB4 is for SCL.
    1st question:
    Is it mandatory that i use these ports to communicate with the eeprom ?
    ( this may be a silly question but for 12F675 i can use almost any pin for them ).
    In the datasheet i have found that we need to clear SSPEN bit and program the 2 I2C ports as inputs.
    2nd question:
    For that to happen i need to mess with the SSPSTAT and SSPCON ?
    If yes, can you please show me how can these be set ( since i dont understand the meaning of their bits )
    thanks
    You seem to have a bit of a problem with a little bit of everything, but then, that's why you're here...
    PBP's I2C commands pretty much take care of everything for you, no extra work needed, with most chips.
    First off, do you have pull up resistors on SDA/SCL like the manual shows?
    Second...where's the code?
  3. - 19th February 2008, 21:20 #3
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    If you are trying to use the hardware i2c, the 16F88 can't do it--it does not have master i2c capability (only SPI). Therefore, the i2c pin selections are irrelevant--you can connect them anywhere you want, and you'll have to define where they are, and use i2c commands.
  4. - 19th February 2008, 21:22 #4
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    Hello skimask and thanks for your help

    Yes...i have the 4k7 pull ups ( also tryed other resistor values with no success.

    here is the code :

    Code:
    *****

SSPCON.5 = 0                ; Disable SSP Module
TXSTA.5 = 0                 ; Disable AUSART Tx
RCSTA.7 = 0                 ; Disable Serial Port
 

OSCCON          = %01111110 'Internal RC w/ I/Os

INTCON=0

PIE1     = 0
'PIE2    = 0

PIR1                 = 0                   'off

CMCON= 7                
CVRCON= 0                   'Vref Off
CCP1CON= 0

T1CON= 0
'T2CON = %00000100

'*****************************************************************************
'DEFINEs
'*****************************************************************************

@ DEVICE INTRC_OSC
@ DEVICE MCLR_OFF
@ DEVICE PROTECT_OFF

DEFINE osc 4

@ DEVICE CPD_OFF
@ DEVICE LVP_OFF
@ DEVICE BOD_OFF
@ DEVICE PWRT_OFF
@ DEVICE WDT_OFF
 
'*****************************************************************************
'ADC

DEFINE ADC_BITS 10 ' Set number of bits in result ( 8 or 10 bits )
DEFINE ADC_CLOCK 3 ' Set clock source (3=rc)
DEFINE ADC_SAMPLEUS 50 ' Set sampling time in uS
 

'*****************************************************************************
'ADC parameters

ADCON1  =%10000000      'right justify
ANSEL   =%00000101 
ADCON0  =%11000001     

'*****************************************************************************
 
INCLUDE "modedefs.bas" 

'settings for serial comm

DEFINE debug_reg PORTA  
DEFINE debug_bit 1
DEFINE debug_baud 9600
DEFINE debug_mode 1

'*****************************************************************************
'I/O's
 
PORTA=0
PORTB=0

TRISA=%00100101
TRISB=%00000011
 
'*****************************************************************************
'PINS
 
temp    var PORTA.0 
out     var PORTA.1 
volt    var PORTA.2 
a3      var PORTA.3 
A4      var PORTA.4 
but1    var PORTA.5 
led2    var PORTA.6 
led1    var PORTA.7 

but2    var PORTB.0   
but3    var PORTB.1   
SCL     var PORTB.2  
SDA     var PORTB.3

green    var PORTB.4  
red       var PORTB.5  
led4      var PORTB.6  
led3      var PORTB.7

*****************************************************************************
' variables

va       var word
va2      var word
tempe    var word
volte    var word
mem      var byte
p1a      var word
p1b      var word
p2a      var word
p2b      var word
p3a      var word
p3b      var word
p4a      var word
p4b      var word
state   var byte
st      var word
ed      var word
ADDR    var word
m1      var  byte
m2      var byte
m3      var byte
m4      var byte
slot    var bit
w       var byte
CTW     VAR BYTE
km      var byte
ra      var word
set1    VAR BYTE
set2    VAR BYTE
rm      var byte
x       var byte

CLEAR

'*****************************************************************************

mem=1       
state=1     
p1a=$10     
p1b=$1070    
p2a=$1080
p2b=$2140
p3a=$2160
p3b=$3220
p4a=$3230
p4b=$4290

'*****************************************************************************
start:

high out
debug $0D, $0A
PAUSE 50

CTW=$A0

'*****************************************************************************

debug "start menu",13,10

startmenu:
 
I2CREAD SDA,SCL,CTW,1,[m1]
I2CREAD SDA,SCL,CTW,2,[m2]
I2CREAD SDA,SCL,CTW,3,[m3]
I2CREAD SDA,SCL,CTW,4,[m4]
 

if (mem=1) and (m1=0) then
led1=1
led2=0
led3=0
led4=0
slot=0
endif
 

if (mem=1) and (m1<>0) then
pause 300
toggle led1
led2=0
led3=0
led4=0
slot=1
endif
 

if (mem=2) and (m2=0) then
led1=0
led2=1
led3=0
led4=0
slot=0
endif
 

if (mem=2) and (m2<>0) then
led1=0
pause 300
toggle led2
led3=0
led4=0
slot=1
endif
 

if (mem=3) and (m3=0) then
led1=0
led2=0
led3=1
led4=0
slot=0
endif
 

if (mem=3) and (m3<>0) then
led1=0
pause 300
led2=0
toggle led3
led4=0
slot=1
endif
 

if (mem=4) and (m4=0) then
led1=0
led2=0
led3=0
led4=1
slot=0
endif
 

if (mem=4) and (m4<>0) then
led1=0
pause 300
led2=0
led3=0
toggle led4
slot=1
endif
 

if state=1 then
green=0
red=1
endif

if state=2 then
green=1
red=0
endif
if state=3 then
green=1
red=1
endif

 

if (but1=1) and (state=1) then
gosub readmenu
endif

if (but1=1) and (state=2) then
gosub recordmenu
endif

if (but1=1) and (state=3) then
gosub erasemenu
endif

 
if but3=1 then
gosub memorymenu
endif

 
if but2=1 then
gosub statemenu
endif


goto startmenu
 

'*****************
recordmenu:

debug "Record Menu",13,10

if slot=1 then 
goto warningmenu
endif

if mem=1 then
st=p1a
ed=p1b
endif
if mem=2 then
st=p2a
ed=p2b
endif
if mem=3 then
st=p3a
ed=p3b
endif
if mem=4 then
st=p4a
ed=p4b
endif

'****************** 

recordmem:
 
debug "2s pause before start recording",13,10
PAUSE 2000


        FOR ADDR= st TO ed

 	for w = 0 to 15
        ADCIN temp, va
        va2=va + (temp>>4)
        NEXT
 
va = (va2 */ 5000 ) >> 2
va=va/10
        
        toggle red
        pause  824           
        debug " Saved value:  ", dec va2," - ", dec va," In position  ", dec ADDR, 13,10 
        debug " VA2 = ", dec va2,13,10
        I2CWRITE SDA,SCL,CTW,ADDR,[VA.highbyte]
        pause 10
        ADDR=ADDR+1
        I2CWRITE SDA,SCL,CTW,ADDR,[VA.lowbyte]
        pause 10    
        ADDR=ADDR+1
        I2CWRITE SDA,SCL,CTW,mem,[addr]
        if but1=1 then      'stop recording
        pause 600
        goto startmenu
        endif
        toggle led1
        toggle led4
        NEXT
        red=1
        return
 
'******************
 
erasemenu:

'*****************

eraseblock:

debug "erasing block",dec mem,13,10
red=0
I2Cread SDA,SCL,CTW,mem,[x]
debug "before in position ",dec mem," - ",dec x,13,10
I2CWRITE SDA,SCL,CTW,mem,[0]
pause 500
red=1
return

'******************

memorymenu:
if mem < 4 then
mem=mem+1
else
mem=1
endif
debug DEC mem,13,10
pause 300
return

'******************

statemenu:

if state < 3 then
state=state+1
else
state=1
endif
debug "state change - ", DEC state,13,10
pause 300
return
 
'******************

end
  5. - 19th February 2008, 21:51 #5
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    WP pin pulled high? Low? Floating?
    Address pins pulled high? Low? Floating?
  6. - 19th February 2008, 22:30 #6
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    WP is connected to ground. Same as all address pins of the eeprom.
  7. - 20th February 2008, 01:22 #7
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    Quote Originally Posted by ruijc View Post
    WP is connected to ground. Same as all address pins of the eeprom.
    Then I'd suggest backing up a bit...
    Get uncomplicated...
    Write some code to just write a few values to the eeprom and read them back to verify what was written...THEN write the code you actually want to use...'cause I see a few flaws in your logic in the code written a few posts back.
  8. - 20th February 2008, 10:40 #8
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    Thanks skimask,

    Good idea. Will do that tonight and post the results

    .
  9. - 20th February 2008, 21:56 #9
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    Just finished assembling a small code and still cannot work with the eeprom

    this is the code i used :

    Code:
    '****************************************************************

'****************************************************************


SSPCON.5 = 0                ; Disable SSP Module
TXSTA.5 = 0                 ; Disable AUSART Tx
RCSTA.7 = 0                 ; Disable Serial Port
 

OSCCON = %01111110 'Internal RC w/ I/Os

INTCON=0

PIE1     = 0
'PIE2    = 0

PIR1 = 0   	'off

CMCON= 7   	'COMPARATOR OFF          
CVRCON= 0 	'Vref Off
CCP1CON= 0

T1CON= 0
'T2CON = %00000100

osctune=0

'*****************************************************************************
'DEFINEs
'*****************************************************************************

@ DEVICE INTRC_OSC
@ DEVICE MCLR_OFF
@ DEVICE PROTECT_OFF

DEFINE osc 8

@ DEVICE CPD_OFF
@ DEVICE LVP_OFF
@ DEVICE BOD_OFF
@ DEVICE PWRT_OFF
@ DEVICE WDT_OFF
 
'*****************************************************************************
 

'*****************************************************************************
'ADC parameters

ADCON1  =%10000000      'right justify
ANSEL   =%00000001 	'PORTA.0 ANALOG
ADCON0  =%11000001     

'*****************************************************************************
 
INCLUDE "modedefs.bas" 

'settings for serial comm

DEFINE debug_reg PORTB  
DEFINE debug_bit 7
DEFINE debug_baud 9600
DEFINE debug_mode 1

'*****************************************************************************
'I/O's
 
PORTA=0
PORTB=0

TRISA=%00000001		'PORTA.0 AS INPUT
TRISB=%00000111		'SDA,SCL AND BUT1 AS INPUTS
 
'*****************************************************************************
'PINS
 
A0    	var PORTA.0 
a1     	var PORTA.1 
A2    	var PORTA.2 
A3      var PORTA.3 
A4      var PORTA.4 
MCLR    var PORTA.5 
a6    	var PORTA.6 
a7    	var PORTA.7 

SDA    	var 	PORTB.0   'I2C DATA PIN
SCL    	var 	PORTB.1   'I2C CLOCK PIN
but1    var 	PORTB.2   'BUTTON FOR LOOP
b3     	var 	PORTB.3

B4    	var PORTB.4  
B5    	var PORTB.5  
B6    	var PORTB.6  
out    	var PORTB.7

'*****************************************************************************
' variables


mem      var 	byte

ADDR    var 	word
m1      var 	word
m2      var 	word
CTW	VAR	WORD

'*****************************************************************************

CTW=$A0
m1=0
m2=0

'*****************************************************************************

start:

I2CREAD SDA,SCL,CTW,$1,[m1]
pause 10

debug " value IN EEPROM address 1 =  ",dec m1,13,10

I2CREAD SDA,SCL,CTW,$10,[m2]
pause 10

debug " value IN EEPROM address 10 =  ",dec m2,13,10

I2CWRITE SDA,SCL,CTW,$1,[5]
PAUSE 10

debug " WROTE 5 at address 1 =  ",13,10

I2CWRITE SDA,SCL,CTW,$10,[6]
PAUSE 10

debug " WROTE 6 at address 10 =  ",13,10


loop:
if but1=1 then 
goto start
else 
goto loop
endif

end
    The value returned for both addresses is 257

    Just as a note, with the first code ( showned in post #4 ) the returned value was always 8 ( for any address ) and 0 when removing the pullups.

    EDIT:
    Changed the lines:

    I2CWRITE SDA,SCL,CTW,$1,[5]

    to

    ADDR=$1
    I2CWRITE SDA,SCL,CTW,ADDR,[5]

    ( as seen in Melanie's post about I2C )
    http://www.picbasic.co.uk/forum/showthread.php?t=587

    but the return value is the same
    Last edited by ruijc; - 20th February 2008 at 22:30.
  10. - 20th February 2008, 23:37 #10
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    Code:
    DEFINE OSC 8
INCLUDE "modedefs.bas" 
@ DEVICE INTRC_OSC
@ DEVICE MCLR_OFF
@ DEVICE PROTECT_OFF
@ DEVICE CPD_OFF
@ DEVICE LVP_OFF
@ DEVICE BOD_OFF
@ DEVICE PWRT_OFF
@ DEVICE WDT_OFF
DEFINE DEBUG_REG PORTB  
DEFINE DEBUG_BIT 7
DEFINE DEBUG_BAUD 9600
DEFINE DEBUG_MODE 1
osccon=$7e:cmcon=7:adcon1=$80:ansel=1:adcon0=$c1:porta=0:portb=0:trisa=1
trisb=7:sda var portb.0:scl var portb.1:addr var word:dat var byte
dat2 var byte:ctw con $a0
start:     dat=dat+1:addr=addr+1
i2cwrite sda,scl,ctw,addr.highbyte,addr.lowbyte,[dat]:pause 10
debug "Wrote: ",dec addr," with ",dec dat,13,10
i2cread sda,scl,ctw,addr.highbyte,addr.lowbyte,[dat2]
debug " Read: ",dec addr," val: ",dec dat2 , 13 , 10
if dat = dat2 then
debug "Write/Read Successful at ",dec5 addr," with ",dec3 dat,13,10
else
debug "Write/Read Error at ",dec5 addr,"-Wrote:",dec3 dat," - Read:",dec dat2,13,10
endif
pause 500:goto start
END
    OR un-COLONized...

    Code:
    DEFINE OSC 8
INCLUDE "modedefs.bas" 
@ DEVICE INTRC_OSC
@ DEVICE MCLR_OFF
@ DEVICE PROTECT_OFF
@ DEVICE CPD_OFF
@ DEVICE LVP_OFF
@ DEVICE BOD_OFF
@ DEVICE PWRT_OFF
@ DEVICE WDT_OFF
DEFINE DEBUG_REG PORTB  
DEFINE DEBUG_BIT 7
DEFINE DEBUG_BAUD 9600
DEFINE DEBUG_MODE 1
osccon = $7e
cmcon = 7
adcon1 = $80
ansel = 1
adcon0 = $c1
porta = 0
portb = 0
trisa = 1
trisb = 7
sda var portb.0
scl var portb.1
addr var word
dat var byte
dat2 var byte
ctw con $a0

start:
dat = dat + 1
addr = addr + 1
i2cwrite sda , scl , ctw , addr.highbyte , addr.lowbyte , [ dat ]
pause 10
debug "Wrote: " , dec5 addr , " with " , dec3 dat , 13 , 10
i2cread sda , scl , ctw , addr.highbyte , addr.lowbyte , [ dat2 ]
debug " Read: " , dec5 addr , " val: " , dec3 dat2 , 13 , 10
if dat = dat2 then
debug "Write/Read Successful at " , dec5 addr , " with " , dec3 dat , 13 , 10
else
debug "Write/Read Error at " , dec5 addr , "-Wrote:" , dec3 dat , " - Read:" , dec dat2 , 13 , 10
endif
pause 500
goto start
END
    Last edited by skimask; - 20th February 2008 at 23:42.
  11. - 21st February 2008, 19:39 #11
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    Hi skimask,

    i'm pleased to say that your code worked. Thank you very much for your help

    Will re-write my entire code from scratch.

    I have some notes here and i will see what happens.

    .
  12. - 21st February 2008, 19:43 #12
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    Quote Originally Posted by ruijc View Post
    Hi skimask,
    i'm pleased to say that your code worked. Thank you very much for your help
    Will re-write my entire code from scratch.
    I have some notes here and i will see what happens.
    .
    Really?
    That's amazing...because I did a quick search a couple days ago for 24LC512 here on THESE forums and, except for COLON-izing the one listing, practically did a cut-and-paste.
    Search engine must've been broken that day...huh?
  13. - 21st February 2008, 20:16 #13
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    I guess i missed that one, sorry.

    But thanks anyway for your help

    .
  14. - 22nd February 2008, 10:58 #14
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    Greetings,

    While reviewing my code i changed the I2C lines from :

    I2Cread SDA,SCL,CTW,mem,[x]

    to

    I2Cread SDA,SCL,CTW,mem.highbyte,mem.lowbyte,[x]

    to make it work.

    Sorry if i'm a bit stubborn ( just trying to learn ), but i re-made ( yes... re-made ) the search and as before almost every one mentions the I2C lines as follows :


    I2cwrite SDA,SCL,CONTROL,ADDR,[DATA]

    Posts like:
    http://www.picbasic.co.uk/forum/show...hlight=24lc512

    http://www.picbasic.co.uk/forum/show...hlight=24lc512

    http://www.picbasic.co.uk/forum/show...hlight=24lc512

    Including melanie's post

    http://www.picbasic.co.uk/forum/showthread.php?t=587

    The only one that mentions to separate the address in high and low somehow did not worked in that case

    http://www.picbasic.co.uk/forum/show...hlight=24lc512


    My question is just to try to understand

    Why is that the i2c line ( I2cwrite SDA,SCL,CONTROL,ADDR,[DATA] ) works with other pics ( yes...all my programs with 12F675 work ) and with the 16F88 does not ? Why with this pic i need to have the address separated with high and low byte ?

    Also ( question for skimask )
    In post # 7 you mention :

    Code:
    'cause I see a few flaws in your logic in the code written a few posts back.
    Can you please point where the flaws are so i can take a look at them ?

    Thanks
  15. - 22nd February 2008, 14:00 #15
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    Quote Originally Posted by ruijc View Post
    Why is that the i2c line ( I2cwrite SDA,SCL,CONTROL,ADDR,[DATA] ) works with other pics ( yes...all my programs with 12F675 work ) and with the 16F88 does not ? Why with this pic i need to have the address separated with high and low byte ?
    Quite frankly, if it works, who cares?
    Actually, I don't remember the answer to that at the moment. I'll remember eventually...

    Also ( question for skimask )
    In post # 7 you mention :
    Code:
    'cause I see a few flaws in your logic in the code written a few posts back.
    Can you please point where the flaws are so i can take a look at them ?
    Thanks
    You'll figure it out... Suffice to say there's just MUCH better ways to do some things, more reliable, faster, longer, stronger, and so on...
  16. - 22nd February 2008, 14:13 #16
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    I've had to make some changes in my logic to work with the new I2C lines ( low/high address ) but still maintained the generic structure.

    This was my priority #1

    After checking if it works will study on those flaws .

    I undestand your point of "if it works, who cares", but if we leave things like that we will never get to improve the codes to be more reliable, faster and shorter

    Dont you agree ?

    In the mean time, if you remember please let me know

    Thanks again
    .
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