storing data in EEPROM

shmow · 2010-07-27 20:09

Hey All,

I'm using Mike Green's Minimal_I2C_Driver (Basic_I2C_Driver - http://obex.parallax.com/objects/26/ . (Thanks Mike!)

I'm trying to understand it, but I'm not sure how to handle devSel or addrReg. What would I put in those variables?

I have the microchip 24LC256 - so, is that device 2 for devSel?

And, addrReg is anywhere from $0000 (0) to $3FFFF ((26000)?

Am I understanding this correctly?

Regards,
Shmow

shmow · 2010-07-27 20:56

Hey All,

here's an attempt to store the value 255 in an EEPROM address (not really sure if it works).
And, an attempt to retrieve what may be in that address too...


CON
    _clkmode = xtal1 + pll16x
    _xinfreq = 5_000_000

    SCL = 28
    StoreData = 255  'VALUE TO BE STORED IN EEPROM
    Ack = 0
    DevSel = $00002  'THE NUMBER TWO IN HEX
    AddrReg = $3FFFF 'ADDRESS LOCATION IN EEPROM 
    count = 32
    
VAR
  byte buffer[noparse][[/noparse]32]
  byte retrievedData     

OBJ
   i2c : "Minimal_I2C_Driver"
   sio : "FullDuplexSerialPlus"
   
PUB Main

  sio.start(31,30,0,115200)
  i2c.initialize(SCL)
  dira[noparse][[/noparse]16..17]~~
' INDICATOR LIGHT TO SHOW PROGRAM WILL START IN 4 SECONDS
' GIVES ME TIME TO OPEN PARALLAX SERIAL TERMINAL
  outa[noparse][[/noparse]17]~~
  waitcnt(clkfreq*4+cnt)
  outa[noparse][[/noparse]17]~  
  repeat                                          
'      WHEN BUTTON IS PRESSED, VALUE OF 255 SHOULD BE STORED IN EEPROM (HOW, I DON'T KNOW) 
       if ina[noparse][[/noparse]0] == 1                     
         StoreVal
         waitcnt(clkfreq*3+cnt)         
       else
'        WHEN BUTTON IS NOT PRESSED, RETRIEVED DATA IS DISPLAYED ON PST (PARALLAX SERIAL TERMINAL)       
         RetrieveVal
         

PRI StoreVal

'    NOT EVEN SURE HOW TO MAKE THIS WORK TO STORE DECIMAL 255 (IN storeData VARIABLE)
'    
     I2C.WritePage(SCL, devSel, addrReg, @buffer, count)
     
PRI RetrieveVal

'  VARIABLE IS ASSIGNED VALUE FROM DEVICE 2 (MICROCHIP 24LC256) AT BUFFER LOCATION 32   
   retrievedData := I2C.ReadPage(SCL, devSel, addrReg, @buffer, Count)
     
'  SHOW DATA ON P SERIAL TERMINAL
   sio.dec(retreivedData)
   sio.Str(string(13," ",13,13))
   waitcnt(clkfreq+cnt)

If you can decipher what I'm trying to do here then throw me a line cause I'm way in over my head!

Cheers,
Shmow

jazzed · 2010-07-27 21:40

I was hoping Mike would jump in ... he may anyway.
In Mike's driver there are read/write examples in the comments.

An EEPROM device id is $A0 ... that's what you get with i2c#EEPROM.
The address range of a 24LC256 is $0000 to $7FFF ... Not sure what $3FFFF will give you.

To store 255 in location 0 you say buffer[noparse][[/noparse]0] := 255 ... but you should read the buffer first.
So a call to Mike's readIt method would preceed that.

Here's a simple, but untested example that should work barring syntax errors, etc....

Hope this helps some way.
--Steve

'' code fragment
obj i2c : "Minimal_I2C_Driver"
var byte buffer[noparse][[/noparse]33] ' I have bad habit of adding 1 to buffers :)
var long eepromAddress

pub main
  eepromAddress := 0  ' global eepromAddress ... not the best way, but ok for demo
  i2c.initialize(28)
  i2c.readIt
  buffer[noparse][[/noparse]eepromAddress // 32] := 255   ' using // 32 makes sure we don't overrun the buffer
  i2c.writeIt
  repeat

PRI readIt
   if i2c.ReadPage(i2c#BootPin, i2c#EEPROM, eepromAddress, @buffer, 32)
     abort ' an error occurred during the read

PRI writeIt | startTime
   if i2c.WritePage(i2c#BootPin, i2c#EEPROM, eepromAddress, @buffer, 32)
     abort ' an error occured during the write
   startTime := cnt ' prepare to check for a timeout
   repeat while i2c.WriteWait(i2c#BootPin, i2c#EEPROM, eepromAddress)
     if cnt - startTime > clkfreq / 10
       abort ' waited more than a 1/10 second for the write to finish

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shmow · 2010-07-27 22:27

Hey Steve,
thanks a'plenty for the helpful reply. I'll run with this to see if I can get things in order.
Cheers,
Shmow

shmow · 2010-07-27 23:05

Hey Steve,

I tested out what you gave me, and I actually got the EEPROM to store my value.
The problem is that when the power is lost and restored, the value is not there in the EEPROM.
Isn't there a way to store a value that won't be lost when the power is interrupted?
Regards,
Shmow

Here's my code with your suggestions:

CON
    _clkmode = xtal1 + pll16x
    _xinfreq = 5_000_000

    SCL = 28
    StoreData = 255  'VALUE TO BE STORED IN EEPROM
    eepromaddress = $0000
    
VAR
  byte buffer[noparse][[/noparse]32]
  byte retrievedData     

OBJ
   i2c : "Minimal_I2C_Driver"
   sio : "FullDuplexSerialPlus"
   
PUB Main

  sio.start(31,30,0,115200)
  i2c.initialize(SCL)
'  i2c.readit
  dira[noparse][[/noparse]16..17]~~
' INDICATOR LIGHT TO SHOW PROGRAM WILL START IN 4 SECONDS
' GIVES ME TIME TO OPEN PARALLAX SERIAL TERMINAL

  outa[noparse][[/noparse]17]~~
  waitcnt(clkfreq*4+cnt)
  outa[noparse][[/noparse]17]~  
  repeat                                          
'      WHEN BUTTON IS PRESSED, VALUE OF 255 SHOULD BE STORED IN EEPROM (HOW, I DON'T KNOW) 
       if ina[noparse][[/noparse]0] == 1                     
         StoreVal
         waitcnt(clkfreq*3+cnt)         
       else
'        WHEN BUTTON IS NOT PRESSED, RETRIEVED DATA IS DISPLAYED ON PST (PARALLAX SERIAL TERMINAL)       
         RetrieveVal
         

PRI StoreVal

  buffer[noparse][[/noparse]eepromAddress // 32] := 255
     
PRI RetrieveVal

'  VARIABLE IS ASSIGNED VALUE FROM DEVICE 2 (MICROCHIP 24LC256) AT BUFFER LOCATION 32   
   retrievedData := buffer[noparse][[/noparse]eepromAddress // 32]
     
'  SHOW DATA ON P SERIAL TERMINAL
   sio.dec(retrievedData)
   sio.Str(string(13," ",13,13))
   waitcnt(clkfreq+cnt)


PRI readIt
   if i2c.ReadPage(i2c#BootPin, i2c#EEPROM, eepromAddress, @buffer, 32)
     abort ' an error occurred during the read

PRI writeIt | startTime
   if i2c.WritePage(i2c#BootPin, i2c#EEPROM, eepromAddress, @buffer, 32)
     abort ' an error occured during the write
   startTime := cnt ' prepare to check for a timeout
   repeat while i2c.WriteWait(i2c#BootPin, i2c#EEPROM, eepromAddress)
     if cnt - startTime > clkfreq / 10
       abort ' waited more than a 1/10 second for the write to finish

jazzed · 2010-07-28 02:08

It seems like you're not calling the writeIt method. Maybe it would help if you add writeIt in StoreVal method after buffer[noparse][[/noparse]eepromAddress // 32] := 255

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shmow · 2010-07-28 02:34

thanks for pointing that out. I would have never known that.
I did the same thing for the readit method too, and it works!
Thanks for your help.

Here's the final sample code for anyone else following:


CON
    _clkmode = xtal1 + pll16x
    _xinfreq = 5_000_000

    SCL = 28
    StoreData = 255  'VALUE TO BE STORED IN EEPROM
    eepromaddress = 0
    
VAR
  byte buffer[noparse][[/noparse]32]
  byte retrievedData     

OBJ
   i2c : "Minimal_I2C_Driver"
   sio : "FullDuplexSerialPlus"
   
PUB Main

  sio.start(31,30,0,115200)
  i2c.initialize(SCL)
'  i2c.readit
  dira[noparse][[/noparse]16..17]~~
' INDICATOR LIGHT TO SHOW PROGRAM WILL START IN 4 SECONDS
' GIVES ME TIME TO OPEN PARALLAX SERIAL TERMINAL

  outa[noparse][[/noparse]17]~~
  waitcnt(clkfreq*4+cnt)
  outa[noparse][[/noparse]17]~  
  repeat                                          
'      WHEN BUTTON IS PRESSED, VALUE OF 255 SHOULD BE STORED IN EEPROM (HOW, I DON'T KNOW) 
       if ina[noparse][[/noparse]0] == 1                     
         StoreVal
         waitcnt(clkfreq*3+cnt)         
       else
'        WHEN BUTTON IS NOT PRESSED, RETRIEVED DATA IS DISPLAYED ON PST (PARALLAX SERIAL TERMINAL)       
         RetrieveVal
         

PRI StoreVal

  buffer[noparse][[/noparse]eepromAddress // 32] := 255
  writeIt
     
PRI RetrieveVal

'  VARIABLE IS ASSIGNED VALUE FROM DEVICE 2 (MICROCHIP 24LC256) AT BUFFER LOCATION 32   
  readit
  retrievedData := buffer[noparse][[/noparse]eepromAddress // 32]
     
'  SHOW DATA ON P SERIAL TERMINAL
   sio.dec(retrievedData)
   sio.Str(string(13," ",13,13))
   waitcnt(clkfreq+cnt)


PRI readIt
   if i2c.ReadPage(i2c#BootPin, i2c#EEPROM, eepromAddress, @buffer, 32)
     abort ' an error occurred during the read

PRI writeIt | startTime
   if i2c.WritePage(i2c#BootPin, i2c#EEPROM, eepromAddress, @buffer, 32)
     abort ' an error occured during the write
   startTime := cnt ' prepare to check for a timeout
   repeat while i2c.WriteWait(i2c#BootPin, i2c#EEPROM, eepromAddress)
     if cnt - startTime > clkfreq / 10
       abort ' waited more than a 1/10 second for the write to finish

Cheers,
Shmow

park1231 · 2010-08-05 06:27

I have been following and am unable to get the code working with an 24LC256. ReadPage is returning with an error. Help would be appreciated.

CON
  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000

  SCL = 28

  eepromAddress = 0

VAR
  byte buffer[noparse][[/noparse]32]
  byte retrieveData

OBJ
  i2c : "Basic_I2C_Driver"
  sio : "FullDuplexSerialPlus"

PUB Main

  sio.start(31,30,0,115200)
  i2c.initialize(SCL)
  dira[noparse][[/noparse]6]~~
  outa[noparse][[/noparse]6]~~
  waitcnt(clkfreq*4+cnt)
  outa[noparse][[/noparse]6]~
  RetrieveValue
  sio.str(string("retrieved",13,13))
  sio.str(string("starting transfer",13))
  StoreValue
  sio.str(string("Stored",13))
  waitcnt(clkfreq*4+cnt)
  RetrieveValue
  sio.str(string("retrieved",13))


PRI readIt
   if i2c.ReadPage(i2c#BootPin, i2c#EEPROM, eepromAddress, @buffer, 32)
     sio.str(string("A Read Error Ocurred",13)) ' an error occurred during the read
     abort

PRI writeIt | startTime
   if i2c.WritePage(i2c#BootPin, i2c#EEPROM, eepromAddress, @buffer, 32)  
     sio.str(string("A Write Error Ocurred",13))
     abort ' an error occured during the write
   startTime := cnt ' prepare to check for a timeout
   repeat while i2c.WriteWait(i2c#BootPin, i2c#EEPROM, eepromAddress)
     if cnt - startTime > clkfreq / 10
       sio.str(string("Waiting Failed",13))' waited more than a 1/10 second for the write to finis
       abort
PRI StoreValue

  buffer[noparse][[/noparse]eepromAddress // 32] := 128
  writeIt
PRI RetrieveValue

  readIt
  retrieveData := buffer[noparse][[/noparse]eepromAddress // 32]

  sio.dec(retrieveData)
  sio.str(string(13," ",13,13))
  waitcnt(clkfreq+cnt)

jmspaggi · 2010-08-05 16:34

Shmow,

Just be careful with that:

  repeat                                          
'      WHEN BUTTON IS PRESSED, VALUE OF 255 SHOULD BE STORED IN EEPROM (HOW, I DON'T KNOW) 
       if ina[noparse][[/noparse]0] == 1                     
         StoreVal
         waitcnt(clkfreq*3+cnt)

Let's say it takes about 40 instruction to execute it. 20 instructions is 20*12.5ns = 0.25us.

If you keep your finger for 1sec on the button, you will execute this loop 4000 times.

An EEPROM can write about 1 000 000 times a value. Then you can have failures and you will have to replace it. So 1 000 000 / 4 000 = 250...

So if you try your program more than 250 times, you will burn your EEPROM.

Just update your code with that:

  repeat                                          
'      WHEN BUTTON IS PRESSED, VALUE OF 255 SHOULD BE STORED IN EEPROM (HOW, I DON'T KNOW) 
       if ina[noparse][[/noparse]0] == 1
         repeat while ina[noparse][[/noparse]0] == 1 ' Add this line to wait until the button is released to store the data only one time.
         StoreVal
         waitcnt(clkfreq*3+cnt)

Just be aware that this will old this cog until you release the button. For my onw project, I have a single cog to handle the inputs, so it's not olding anything on the other cogs.

JM

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lardom · 2010-08-09 07:37

I learned that a variable occupies the same address in memory and ram. The obex has an object called "BS2_Functions". The method, I think, is "Write_Codemem". At any rate I assigned a keypad button to write a variable to eeprom. It easily changes default values which persist through resets.

storing data in EEPROM

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