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Add single-byte write and read functions.
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Remove support for Arduino releases before 1.0.
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JChristensen committed Jul 21, 2014
1 parent 36156f5 commit c2d7fff
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75 changes: 55 additions & 20 deletions extEEPROM.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,23 @@
* *
* This library will work with most I2C serial EEPROM chips between 2k bits *
* and 2048k bits (2M bits) in size. Multiple EEPROMs on the bus are supported *
* as a single address space. Certain assumptions are made regarding the *
* EEPROM device addressing. These assumptions should be true for most EEPROMs *
* as a single address space. I/O across block, page and device boundaries *
* is supported. Certain assumptions are made regarding the EEPROM *
* device addressing. These assumptions should be true for most EEPROMs *
* but there are exceptions, so read the datasheet and know your hardware. *
* *
* The library should also work for EEPROMs smaller than 2k bits, assuming *
* that there is only one on the bus and also that the user is careful not *
* to exceed the maximum address for the EEPROM. *
* that there is only one EEPROM on the bus and also that the user is careful *
* to not exceed the maximum address for the EEPROM. *
* *
* Library tested with: *
* Microchip 24AA02E48 (2k bit) *
* Microchip 24LC256 (256k bit) *
* Microchip 24FC1026 (1M bit, thanks to Gabriele B on the Arduino forum) *
* ST Micro M24M02 (2M bit) *
* *
* Library will NOT work with Microchip 24xx1025 as its control byte does not *
* conform to the following assumptions. *
* *
* Device addressing assumptions: *
* 1. The I2C address sequence consists of a control byte followed by one *
Expand All @@ -27,6 +37,7 @@
* Depending on EEPROM device size, this may result in one or more of the *
* most significant bits in the I2C address bytes being unused (or "don't *
* care"). *
* 4. An EEPROM contains an integral number of pages. *
* *
* To use the extEEPROM library, the Arduino Wire library must also *
* be included. *
Expand All @@ -51,6 +62,7 @@
// - nDevice is the number of EEPROM devices on the I2C bus (all must
// be identical).
// - pageSize is the EEPROM's page size in bytes.
// - eepromAddr is the EEPROM's I2C address and defaults to 0x50 which is common.
extEEPROM::extEEPROM(eeprom_size_t deviceCapacity, byte nDevice, unsigned int pageSize, uint8_t eepromAddr)
{
_dvcCapacity = deviceCapacity;
Expand All @@ -76,23 +88,23 @@ extEEPROM::extEEPROM(eeprom_size_t deviceCapacity, byte nDevice, unsigned int pa

//initialize the I2C bus and do a dummy write (no data sent)
//to the device so that the caller can determine whether it is responding.
//when using a 400kHz clock speed and there are multiple I2C devices on the
//when using a 400kHz bus speed and there are multiple I2C devices on the
//bus (other than EEPROM), call extEEPROM::begin() after any initialization
//calls for the other devices to ensure the intended I2C clock speed is set.
byte extEEPROM::begin(twiClockFreq_t twiFreq)
{
Wire.begin(_eepromAddr);
TWBR = ( (F_CPU / twiFreq) - 16) / 2;
Wire.beginTransmission(_eepromAddr);
if (_nAddrBytes == 2) i2cWrite(0); //high addr byte
i2cWrite(0); //low addr byte
if (_nAddrBytes == 2) Wire.write(0); //high addr byte
Wire.write(0); //low addr byte
return Wire.endTransmission();
}

// Write bytes to external EEPROM.
// If the I/O would extend past the top of the EEPROM address space,
// a status of EEPROM_ADDR_ERR is returned. For I2C errors, the status
// from the Arduino Wire library is passed back through to the caller.
//Write bytes to external EEPROM.
//If the I/O would extend past the top of the EEPROM address space,
//a status of EEPROM_ADDR_ERR is returned. For I2C errors, the status
//from the Arduino Wire library is passed back through to the caller.
byte extEEPROM::write(unsigned long addr, byte *values, byte nBytes)
{
uint8_t ctrlByte; //control byte (I2C device address & chip/block select bits)
Expand All @@ -111,18 +123,18 @@ byte extEEPROM::write(unsigned long addr, byte *values, byte nBytes)
nWrite = BUFFER_LENGTH - _nAddrBytes < nWrite ? BUFFER_LENGTH - _nAddrBytes : nWrite;
ctrlByte = _eepromAddr | (byte) (addr >> _csShift);
Wire.beginTransmission(ctrlByte);
if (_nAddrBytes == 2) i2cWrite( (byte) (addr >> 8) ); //high addr byte
i2cWrite( (byte) addr ); //low addr byte
i2cWrite(values, nWrite);
if (_nAddrBytes == 2) Wire.write( (byte) (addr >> 8) ); //high addr byte
Wire.write( (byte) addr ); //low addr byte
Wire.write(values, nWrite);
txStatus = Wire.endTransmission();
if (txStatus != 0) return txStatus;

//wait up to 50ms for the write to complete
for (uint8_t i=100; i; --i) {
delayMicroseconds(500); //no point in waiting too fast
delayMicroseconds(500); //no point in waiting too fast
Wire.beginTransmission(ctrlByte);
if (_nAddrBytes == 2) i2cWrite(0); //high addr byte
i2cWrite(0); //low addr byte
if (_nAddrBytes == 2) Wire.write(0); //high addr byte
Wire.write(0); //low addr byte
txStatus = Wire.endTransmission();
if (txStatus == 0) break;
}
Expand Down Expand Up @@ -156,17 +168,40 @@ byte extEEPROM::read(unsigned long addr, byte *values, byte nBytes)
nRead = BUFFER_LENGTH < nRead ? BUFFER_LENGTH : nRead;
ctrlByte = _eepromAddr | (byte) (addr >> _csShift);
Wire.beginTransmission(ctrlByte);
if (_nAddrBytes == 2) i2cWrite( (byte) (addr >> 8) ); //high addr byte
i2cWrite( (byte) addr ); //low addr byte
if (_nAddrBytes == 2) Wire.write( (byte) (addr >> 8) ); //high addr byte
Wire.write( (byte) addr ); //low addr byte
rxStatus = Wire.endTransmission();
if (rxStatus != 0) return rxStatus; //read error

Wire.requestFrom(ctrlByte, nRead);
for (byte i=0; i<nRead; i++) values[i] = i2cRead();
for (byte i=0; i<nRead; i++) values[i] = Wire.read();

addr += nRead; //increment the EEPROM address
values += nRead; //increment the input data pointer
nBytes -= nRead; //decrement the number of bytes left to write
}
return 0;
}

//Write a single byte to external EEPROM.
//If the I/O would extend past the top of the EEPROM address space,
//a status of EEPROM_ADDR_ERR is returned. For I2C errors, the status
//from the Arduino Wire library is passed back through to the caller.
byte extEEPROM::write(unsigned long addr, byte value)
{
return write(addr, &value, 1);
}

//Read a single byte from external EEPROM.
//If the I/O would extend past the top of the EEPROM address space,
//a status of EEPROM_ADDR_ERR is returned. For I2C errors, the status
//from the Arduino Wire library is passed back through to the caller.
//To distinguish error values from valid data, error values are returned as negative numbers.
int extEEPROM::read(unsigned long addr)
{
uint8_t data;
int ret;

ret = read(addr, &data, 1);
return ret == 0 ? data : -ret;
}
36 changes: 18 additions & 18 deletions extEEPROM.h
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Original file line number Diff line number Diff line change
@@ -1,15 +1,25 @@
/*-----------------------------------------------------------------------------*
* extEEPROM.cpp - Arduino library to support external I2C EEPROMs. *
* extEEPROM.h - Arduino library to support external I2C EEPROMs. *
* *
* This library will work with most I2C serial EEPROM chips between 2k bits *
* and 2048k bits (2M bits) in size. Multiple EEPROMs on the bus are supported *
* as a single address space. Certain assumptions are made regarding the *
* EEPROM device addressing. These assumptions should be true for most EEPROMs *
* as a single address space. I/O across block, page and device boundaries *
* is supported. Certain assumptions are made regarding the EEPROM *
* device addressing. These assumptions should be true for most EEPROMs *
* but there are exceptions, so read the datasheet and know your hardware. *
* *
* The library should also work for EEPROMs smaller than 2k bits, assuming *
* that there is only one on the bus and also that the user is careful not *
* to exceed the maximum address for the EEPROM. *
* that there is only one EEPROM on the bus and also that the user is careful *
* to not exceed the maximum address for the EEPROM. *
* *
* Library tested with: *
* Microchip 24AA02E48 (2k bit) *
* Microchip 24LC256 (256k bit) *
* Microchip 24FC1026 (1M bit, thanks to Gabriele B on the Arduino forum) *
* ST Micro M24M02 (2M bit) *
* *
* Library will NOT work with Microchip 24xx1025 as its control byte does not *
* conform to the following assumptions. *
* *
* Device addressing assumptions: *
* 1. The I2C address sequence consists of a control byte followed by one *
Expand All @@ -27,6 +37,7 @@
* Depending on EEPROM device size, this may result in one or more of the *
* most significant bits in the I2C address bytes being unused (or "don't *
* care"). *
* 4. An EEPROM contains an integral number of pages. *
* *
* To use the extEEPROM library, the Arduino Wire library must also *
* be included. *
Expand All @@ -43,20 +54,7 @@
#ifndef extEEPROM_h
#define extEEPROM_h

#if defined(ARDUINO) && ARDUINO >= 100
#include <Arduino.h>
#else
#include <WProgram.h>
#endif

//define release-independent I2C functions
#if ARDUINO >= 100
#define i2cRead Wire.read
#define i2cWrite Wire.write
#else
#define i2cRead Wire.receive
#define i2cWrite Wire.send
#endif

//EEPROM size in kilobits. EEPROM part numbers are usually designated in k-bits.
enum eeprom_size_t {
Expand Down Expand Up @@ -84,7 +82,9 @@ class extEEPROM
extEEPROM(eeprom_size_t deviceCapacity, byte nDevice, unsigned int pageSize, byte eepromAddr = 0x50);
byte begin(twiClockFreq_t twiFreq = twiClock100kHz);
byte write(unsigned long addr, byte *values, byte nBytes);
byte write(unsigned long addr, byte value);
byte read(unsigned long addr, byte *values, byte nBytes);
int read(unsigned long addr);

private:
uint8_t _eepromAddr; //eeprom i2c address
Expand Down
1 change: 1 addition & 0 deletions keywords.txt
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
extEEPROM KEYWORD1
begin KEYWORD2
write KEYWORD2
read KEYWORD2

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