cubloc:reading_from_and_writing_to_an_eeprom:index

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====== Reading from and Writing to an EEPROM ======

Typically EEPROMs store between 0.5 to 64KB of data. Data is retained
even after powering off. For example, if you wanted to retain a temperature
setting for a temperature controller, you could simply store the value of the
temperature in the EEPROM in case of a power outage.

The Cubloc has an internal EEPROM of 4KB. This EEPROM can be used to
store small amounts of data. If a larger EEPROM is needed, the 24LC512
can be used to store up to 64KB of data.

The following example will demonstrate how to access the 24LC32 4KB
EEPROM using the I2C protocol. Serial EEPROMs usually support either SPI
or I2C. I2C EEPROM part numbers begin with 24XXXX and SPI EEPROM
part numbers begin with 93XXX.

{{ :cubloc:reading_from_and_writing_to_an_eeprom:cubloceeprom.png?nolink |}}


<code xbasic>
Const Device = CB220
Dim adr As Integer
Dim data As Byte
Dim a As Byte
data = &ha6
adr = &h3
Set I2C 7,6
Do
  I2CStart
  If I2CWrite(&b10100000)= 1 Then Goto err_proc
  a=I2CWrite(adr.byte1)
  a=I2CWrite(adr.lowbyte)
  a=I2CWrite(data)
  I2CStop
  Delay 1000
  I2CStart
  a=I2CWrite(&b10100000)
  a=I2CWrite(adr.byte1)
  a=I2CWrite(adr.lowbyte)
  I2CStart
  a=I2CWrite(&b10100001)
  a=I2CRread(0)
  I2CStop
  Debug Hex a,cr
  ADR = ADR + 1
  DATA = DATA + 1
Loop
 
err_proc:
  Debug "Error !"
  Do
  Loop
</code>

This example program will write a number to the EEPROM and read it back.
When this program runs correctly, numbers will increment in the debug
window. This program can be easily modified to support other EEPROMs.

Note: Typically, EEPROMs need a delay of about 5ms after a write operation.

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