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Topic: 24LC256 overwrite and read all sketches (Read 3211 times) previous topic - next topic

Volkemon

Jul 26, 2010, 12:00 am Last Edit: Jul 26, 2010, 04:36 pm by Volkemon Reason: 1
Couple of sketches I made as I learned about the 24LC256.

This one overwrites all the data with FF, or whatever value you choose to substitite. it does it in (2) 30 packet strings, and one (4) packet string. This puts the Internal Address Pointer at the beginning of a Page each time the cycle is complete.


**EDIT** I discovered at the end of the process, after the "OVERWRITE COMPLETE" message, the 'startAddress' value was 1 not 0. I could find no reason for this in the code.  I put a workaround in , I set the value of 'startAddress' to (-1) and things work fine.  I am open to reasons why, however :) **

New Sketch:
Code: [Select]

// Some code to overwrite FF (or other chosen value) in all memory locations in a 24LC256.
// mashup from Volkemon 7/2010



#include <Wire.h>  


char chipAdress=0x50;   // 24LC256 address on the bus, pins a0,a1 and a2 tied to ground. Will not compile as a byte value, only char??


int startAddress = 0;      //overall counter for address location. 16 bit value, will be split into MSB and LSB  
byte startaddrMSB = 0x00; // Most Signifigant Byte, 1/2 of the address in chip memory.         Max val 0x7F
byte startaddrLSB = 0x00; // Least Signifigant Byte, other 1/2 of the address in chip memory.  Max val 0xFF
                     



void setup()

{
 Wire.begin();             // enable the i2c bus
 Serial.begin(19200);      // Make sure you set the serial monitor to match! :)


}



void loop()
{

 
   Serial.print("Writing starting at bite/slot "); Serial.print(startAddress, DEC);  // info sent to serial monitor for debugging.
 Wire.beginTransmission(chipAdress);    // chip address on the TWI bus, not chip memory address.
 
                 //Set up the chip Internal Address Pointer to the desired location
                 
 startaddrMSB = highByte(startAddress);
 startaddrLSB = lowByte(startAddress);  
 Wire.send(startaddrMSB);      //First  7 bits of the address
 Wire.send(startaddrLSB);     //Second 8 bits of the address
 
 for (byte ct=0x0; ct<30; ct++)  // loop where we write info to Wire library buffer.30 byte max. first two are used for address.
 {
   
  Wire.send(0xF1);
  startAddress ++;
  if (startAddress >= 0x7FFF){
    Serial.print("OVERWRITE COMPLETE");
    startAddress = (-1);    // if set to zero, address is off by 1 after 1st overwrite. WHY???
    delay(5000);
  }
                   
 }
 Wire.endTransmission();      // commands write of data from Wire library buffer to chip , 'closes' chip
 
 Serial.print(" Done1.");Serial.print(startAddress);
 
 
 
 
 
 
  Wire.beginTransmission(chipAdress);    // chip address on the TWI bus, not chip memory address.
 
                 //Set up the chip Internal Address Pointer to the desired location
 startaddrMSB = highByte(startAddress);
 startaddrLSB = lowByte(startAddress);  
 Wire.send(startaddrMSB);      //First  7 bits of the address
 Wire.send(startaddrLSB);     //Second 8 bits of the address
 
 for (char ct=0x0; ct<30; ct++)  // loop where we write info to Wire library buffer.30 byte max.first two used by address.
 {
   
  Wire.send(0xF2);   // Sends the value 0xFF to Wire library buffer.
  startAddress++;
  if (startAddress >= 0x7FFF){
    Serial.print("OVERWRITE COMPLETE");
    startAddress = (-1);   // if set to zero, address is off by 1 after 1st overwrite. WHY???
    delay(5000);
  }
 }
 
 Wire.endTransmission();      // commands write of data from Wire library buffer to chip , 'closes' chip
 
 Serial.print(" Done2.");Serial.print(startAddress);

// The first two wire.send loops sent 60 packets, leaving 4 open in the page. This cleans them up, and gets the Internal Address Pointer to an page beginning.


   Wire.beginTransmission(chipAdress);    // chip address on the TWI bus, not chip memory address.
 
                 //Set up the chip Internal Address Pointer to the desired location
 startaddrMSB = highByte(startAddress);
 startaddrLSB = lowByte(startAddress);  
 Wire.send(startaddrMSB);      //First  7 bits of the address
 Wire.send(startaddrLSB);     //Second 8 bits of the address
 
 for (char ct=0x0; ct<4; ct++)  // loop where we write info to Wire library buffer.4 to clean up the page.
 {
   
  Wire.send(0xF3);   // Sends the value 0xFF to Wire library buffer.
  startAddress++;
  if (startAddress >= 0x7FFF){
    Serial.print("OVERWRITE COMPLETE");
    startAddress = (-1);     // if set to zero, address is off by 1 after 1st overwrite. WHY???
    delay(5000);
  }
 }
 
 Wire.endTransmission();      // commands write of data from Wire library buffer to chip , 'closes' chip
 
  Serial.print(" Done3."); Serial.println(startAddress);
 
}


This one reads all the data off the card. The data can be read only in 32 byte strings due to limitations in the wire library. starts at the beginning, and goes to the end, actually beyond.. :)

**EDIT** I had forgotten to put code in the setup loop to put the Internal Address Pointer back to '0'.... ::)

Code: [Select]


// sketch to read entire chip 32 bytes at a time, display on serial monitor with progress indicated.
// July2010- Volkemon tweaked and commented.
//      _ _
//  A0-|oU |-Vcc
//  A1-|   |-WP
//  A2-|   |-SCL
// Vss-|   |-SDA
//      ---
//
//   SDA goes to Arduino 4
//   SCL goes to Arduino 5
//   WP  goes to ground for now. Can be put to Vcc if write protection is needed.
//   Vcc goes to arduino Vcc
//   Vss goes to arduino ground
//   A2, A1, A0 go to ground for now.
//
// They can be also put to either ground or Vcc to control up to 8 memory chips (2^3), giving you 2MBit of memory (8*2^15).
// A2 A1 A0 Binary Address Hex Address
// 0  0  0    0b1010000       0×50
// 0  0  1    0b1010001       0×51
// 0  1  0    0b1010010       0×52
// 0  1  1    0b1010011       0×53
// 1  0  0    0b1010100       0×54
// 1  0  1    0b1010101       0×55
// 1  1  0    0b1010110       0×56
// 1  1  1    0b1010111       0×57
 
#include <Wire.h>

char chipAdress=0x50;        // Binary 10100000 . Three bits after 1010 (currently 000) are used to specify to what A2, A1, A0 are connected to, ground or vcc. See comment above.
                     // Last bit specifies the opertation - 0 for write, 1 for read. This is controlled for you by the Wire library. :)
int block = 0;



void setup()

{
 Wire.begin();           // enable the i2c bus
 Serial.begin(19200);   // Did you set your serial monitor to 19200?
 Wire.beginTransmission(chipAdress);    // chip address on the TWI bus, not chip memory address.
 
                 //Set up the chip Internal Address Pointer to the beginning of memory

 Wire.send(0x00);      
 Wire.send(0x00);    
 
 Wire.endTransmission(); // sends Wire buffer to chip, sets Internal Address Pointer to '0'
 
 
}

void loop()
{
 Serial.println("");
 Serial.print(block);
 Wire.requestFrom(chipAdress, 32);          // requests 32 Bytes of data in a packet, maximum string size.
 while(Wire.available()){                // 'while loop' start, Checks to see if data is waiting
   Serial.print("  ");                  // space to format packets on serial monitor
   Serial.print(Wire.receive(), HEX);  // print the values received on the serial monitor
 }                                    // end bracket for 'while loop'
 Wire.endTransmission();           // when 'while loop' is finished (no more data available) 'closes' chip
 //Serial.println("");
 block += 1;
 if (block > 1024){
   Serial.println("End Of Memory");
   delay(5000);
 }
 delay(100);
}

Hope it helps someone... I learned a lot about these little chips today!!

retrolefty

Thanks for your posting. I did use a 24LC256 chip in my last project to save script patterns for a LED cube. However I only performed single byte reads and writes. I think it would be cool to build a shield for eight of these puppies mounted on it. Been looking for a bargain price of a bunch of them on E-bay, but so far haven't found a listing I like.

Lefty

Volkemon

I found the 24LC512 for $1.40 each from Newark, same footprint and pinout, but twice the memory for your shield.

http://www.newark.com/jsp/search/productdetail.jsp?SKU=62K0581&CMP=AFC-GB100000001  

I am sure there are others, I just happened to start here.


retrolefty

Wow that's a great price and Newark doesn't charge me shipping! I just ordered eight of them.

Thanks for the info

Lefty

Volkemon

Hm...no shipping?!? I may have to look into that. I just googled it.

Well, the 'page wrap' during writes had been the major problem in reliable data logging for me using the 24LC256.

Using the two sketches above, and writing values such as F1,F2,F3 and observing the patterns shown by reading it, have proved valueable in writing information properly to the chip.

This may free me from using a SD card that is WAY too big for my purpose. SWEET!

Now... to transmit it via XBee to a roving monitor... :)  

Garitron

Hello Volkemon...

I have implemented your overwrite sketch.  It was a good mechanism for learning how to work with the 24LC256.  You had a couple of problems:

1) Can't get "chipAdress" to compile using "byte", need "char"...
   Mine works fine with "byte", I don't know why... (uint8_t would
   probably be better.)

2) Your off-by-one problem:
   a) Change "int startAddress = 0" to "uint16_t startAddress = 0"
       (Signed integer changed to unsigned.)

   b) Change (3) tests to "if (startAddress > 0x7FFF) {"
       (address 0x7FFF didn't get written until next pass using -1,
        I think. This is probably the root of the problem.)

   c) Change (3) reset stmts to "startAddress = 0;"

   Anyhow, it works now...

Hope you sleep better tonight!

73,
 Gary (Garitron)

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