CB-029 32k x 8-bit EEPROM Module - Jameco Electronics · 2014. 11. 6. · The CB-029 EEPROM has 256k bits arranged as 32k 8-bit words. This note will show how to write to and reading

_____________________________________________________________________________________

Rev. 1.01

r e v . 1 . 0 1 145 Rt. 46 West E‐mail: sales@electro‐set.net Wayne, NJ 07470 Web: www.Electro‐Set.net

1

CB-029 32k x 8-bit EEPROM Module

September 05, 2014

Introduction

This application note will show two minimal code set ups to operate the EEPROM module CB-029 one with an Arduino board and the other with Cardinal’s CB-026 Microchip microcontroller module.

The CB-029 EEPROM has 256k bits arranged as 32k 8-bit words. This note will show how to write to and reading from the EEPROM.

Arduino

The Arduino example will write a text phrase to the EEPROM, read it back and count the occurrence of the letter ‘a’ in the read phrase. The Arduino serial monitor port will be used to display the result.

Before proceeding any further, please have the Arduino software install to your computer. Visit Arduino’s user setup guide at http://arduino.cc/en/Guide/windows for step-by-step instructions.

Hardware

Parts List:

Arduino Uno USB type B connector CB-I-022 Cardinal Interface Board CB-029 EEPROM module

_____________________________________________________________________________________

Rev. 1.01


2

Connect the components as shown in the picture below

Plug the CB-I-022 interface into the Arduino Uno board and the CB-029 EEPROM module into the interface’s Electro-Set 6 pin connector. Connect the USB cable between the computer and the Arduino Uno.

The computer will supply 5 volts through the USB cable which will be regulated on the Arduino interface board to 3.3 volts to run the CB-029 EEPROM module.

Three jumpers on the CB-029 can be used to change the slave address of the EEPROM. For this code example we are using 0x57 as the 7-bit slave address so the three jumper should be populated towards the center of the board as shown in the picture above. This makes the lower three slave address bits a logic one (high), the 7 in 0x57 slave address.

_____________________________________________________________________________________

Rev. 1.01


3

The Software

#include <Wire.h> // Wire I2C library

#define EEPROM_ADDRESS 0x57 // 7-bit I2C EEPROM_ADDRESS of eeprom

static char someText[] = "Mary had a little lamb it's fleece was white as snow.";

unsigned int index = 0;

unsigned int len,i;

char myChar;

unsigned int count=0;

void setup()

{

Serial.begin(9600); // initialize serial monitor to 9600 baud

Serial.println("Electro-Set"); // welcome message

Serial.println("CB-029 Test"); // welcome message

Wire.begin(); // initialize I2C port

len=strlen(someText); // the length of the text to write, the number of bytes

Serial.print("The number of characters in someText to write is ");

Serial.println(len); // print number of bytes to serial monitor

}

void loop()

{

Serial.println("Writing:"); // Display info to the serial monitor

while(index<len){ // A while loop to write the text to eeprom

_____________________________________________________________________________________

Rev. 1.01


4

Wire.beginTransmission(EEPROM_ADDRESS); // start of I2C tramsmission to eeprom

Wire.write(index>>8); // MSB of 16-bit eeprom memory address

Wire.write(index&0xff); // LSB of 16-bit eeprom memory address

Wire.write(someText[index]); // data byte to write to eeprom memory

Wire.endTransmission(); // Complete the I2C transmission

delay(5); // The delay is very important, the eeprom write is slow

Serial.print(someText[index]); // Display the text being written to the serial monitor

index++; // Increment the index

} // end of while()

Serial.println(); // New line

Serial.println("Reading:"); // Display info to the serial monitor

for(i=0;i<len;i++){ // A for loop to read back the text and count the 'a's

Wire.beginTransmission(EEPROM_ADDRESS); // start of I2C tramsmission to eeprom

Wire.write(i>>8); // MSB of 16-bit eeprom memory address

Wire.write(i&0xff); // LSB of 16-bit eeprom memory address

Wire.endTransmission(); // Complete the I2C transmission

Wire.requestFrom(EEPROM_ADDRESS, 1); // Read 1 bytes from eeprom into Wire input buffer

if(Wire.available() == 1){ // If we received one bytes, that is good

myChar=Wire.read(); // retrieve the byte from the buffer

Serial.print(myChar); // display the char read on the serial monitor

if (myChar=='a') // compare the character with the charater 'a'

count++; // if it matches add 1 to the count

}

} // end of for()

Serial.println(); // New line

Serial.println("Result:"); // Display info to the serial monitor

Serial.print("Number of 'a' is "); // Output the count to the serial monitor

_____________________________________________________________________________________

Rev. 1.01


5

Serial.println(count);

while(1); // Go no further, we are done, loop forever

} // end of loop()

Code Operation

The EEPROM module has a 7-bit I2C slave address as 0x57 which we make a #define.

The setup() function is called when sketch starts. The setup code, initializes the serial monitor baud rate at 9600, outputs a welcome message and then initializes the I2C port as a master. We compute the length of the text phrase stored in the “someText” array and output this length (‘len’) to the serial monitor which for our example turns out to be 53 bytes.

After setup has completed, sketch causes the function loop() to be repeatedly called.

The variable ‘index’ is used to access through the “someText” array and is also used as the memory address in the EEPROM. The EEPROM memory address is 16-bits wide, we use the upper byte of ‘index’ for the MSB of the EEPROM address and the lower byte of ‘index’ for the LSB of the EPROM address. In our example the MSB will always be 0x00 and LSB will range from 0x00 to 0x52. The ‘while’ loop takes one byte at a time from the ‘someText’ array and writes it to the EEPROM, looping ‘len’ (53) time to completely write the phrase.

Take special note of the ‘delay(5);’ code line. Without this the writes to EEPROM will be arriving too fast for the EEPROM and will be discarded. The write cycle time from the datasheet is specified at 5mS.

Next the code reads back the values from the EEPROM using a ‘for’ loop (just to be different). As each byte is retrieved it is compared against the character ‘a’, if matching the ‘count’ variable is incremented. Once the ‘for’ loop completes its 53 iterations, the value of the ‘count’ variable is output to the serial monitor. Lastly we execute the code ‘while(1);’, this puts the microcontroller into an endless loop doing nothing harmful and causing our code in the sketch ‘loop()’ function to execute only once. As an alternative, we could have placed all our code in the sketch ‘setup()’ function since it only executes once.

_____________________________________________________________________________________

Rev. 1.01


6

Microchip Module CB-026

The CB-026 example in PICBASIC PRO will write 10 data values into the EEPROM on the CB-029 module then read them back displaying the data values via the serial port to a terminal emulator such as hyperterminal

Before proceeding any further, please have the MicroCode Studio PICBASIC PRO suite installed on your computer.

Hardware

Parts List:

Electro-Set module CB-026 microcontroller USB type mini connector CB-029 EEPROM module

_____________________________________________________________________________________

Rev. 1.01


7

Connect the components as shown in the picture below

The Software

INCLUDE "modedefs.bas"

#CONFIG __config _HS_OSC & _WDT_ON & _LVP_OFF & _CP_OFF

#ENDCONFIG

DEFINE OSC 20 'Set for 20 MHz oscillator

SCL var PORTC.3 ‘ Set I2C pins

SDA var PORTC.4

_____________________________________________________________________________________

Rev. 1.01


8

Soutpin var PORTC.6 ‘ Set serial port pins

Sinpin var PORTC.7

baud1 var byte ‘ for serial port baud rate

EEpromadd var word ‘ 16-bit address of where to write the data in the EEPROM

eepromdata var byte ‘ the 8-bit data to write into the EEPROM

baud1 = 6 ‘ 38400 baud, non-inverted

test_EEProm: ‘ label to loop to repeat the sequence

serout2 soutpin,baud1,["TESTING EEProm",13,10] ‘ Welcome message to serial port

serout2 soutpin,baud1,["Writing to the first 10 locations of the EEProm",13,10]

pause 1000 ‘ wait 1 second

for eepromadd = 1 to 10 ‘ loop to cause eepromadd to increment from 1 to 10

eepromdata = eepromadd & $00FF ’ mask the address value to return the lower 8-bits

eepromdata = eepromdata * 2 ‘ double the value

serout2 soutpin, baud1,["Writing Address ",dec2 eepromadd," Data = ",dec2 eepromdata,13,10]

i2cwrite sda,scl,$AE,EEpromadd,[eepromdata],nodata ‘ write the data into the EEPROM

pause 250 ‘ Some delay is very important, EEPROM writes are slow

next eepromadd

pause 500

serout2 soutpin,baud1,["Reading the first 10 locations of the EEProm",13,10]

for eepromadd = 1 to 10 ‘ loop to cause eepromadd to increment from 1 to 10

i2cread sda,scl,$AE,eepromadd,[eepromdata],nodata ‘ read from EEPROM

serout2 soutpin,baud1,["Reading Address ",Dec eepromadd," Data = ",dec2 eepromdata,13,10]

pause 250 ‘ This delay not important, reads of EEPROM are fast

next eepromadd

serout2 soutpin,baud1,["Done",13,10]

pause 500

goto test_eeprom ‘ do it all over again

NoData: ‘ Excute this if the I2C communication fails

_____________________________________________________________________________________

Rev. 1.01


9

Serout2 soutpin,baud1,["EEProm Module Not Connected",13,10]

pause 500

goto Test_EEProm

end

Code Operation

The line

“# CONFIG __config _HS_OSC & _WDT_ON & _LVP_OFF & _CP_OFF”

includes configuration for the programmer in the output hex file so it does not necessary to manually change the entries in the programmer configuration window every time you come to write a new version of your program to the microcontroller.

The port pins for the I2C interface are set on PORTC pins 3 and 4. The CB-026 board wires these to the Electro-Set 6 pin connector.

The microcontroller serial port pins are set on PORTC pins 6 and 7, these connect to the FTDI chip on the CB-026 which couples through to the USB and so when plugged into a PC producing a virtual COMM port where the microcontroller’s serial data can be seen on a terminal emulator such as hyperterminal. The terminal emulator should be set to connect to the virtual COMM port assigned to the FTDI driver and connect at 38400,8,N,1.

We declare the variable baud1 for use in the serout2 to set the baud rate. For a baud rate of 38400, baud1 is set to 6, see the MicroChip documentation for other rates and options.

The first parameters for the PicBasicPro functions i2cread and i2cwrite uses and 8-bit slave address which is a one bit left shift of the 7-bit slave address, so the A/D module’s 8-bit slave address as 0xAE.

The line

for eepromadd = 1 to 10

sets up a ‘for’ loop to sequentially increment the 16-bit word variable eepromadd from 1 to 10. These are the address locations we will write to in this example. In this loop we take the lower 8-bits of eepromadd, double that value and save the result in the byte variable eepromdata, this is the value we will write using the following line of code:

i2cwrite sda,scl,$AE,EEpromadd,[eepromdata],nodata ‘ write the data into the EEPROM

Between successive writes to the EEPROM we need some delay, around 5mS. Without this delay the write will be rejected by the EEPROM.

_____________________________________________________________________________________

Rev. 1.01


10

Finally we set up another ‘for’ loop to read and display the data on the serial port.

.

Documents

CB-029 32k x 8-bit EEPROM Module - Jameco Electronics · 2014. 11. 6. · The CB-029 EEPROM has 256k bits arranged as 32k 8-bit words. This note will show how to write to and reading