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Bit-banged I2C implementation on any pin

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This commit is contained in:
Rhys Weatherley 2012-05-13 22:41:10 +10:00
parent 9a1cd00521
commit cbd5345b49
3 changed files with 272 additions and 1 deletions
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doc/Doxyfile
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@ -610,7 +610,7 @@ WARN_LOGFILE =
# directories like "/usr/src/myproject". Separate the files or directories
# with spaces.
INPUT = ../libraries/FreetronicsLCD ../libraries/BlinkLED .
INPUT = ../libraries/FreetronicsLCD ../libraries/BlinkLED ../libraries/BitBangI2C .
# This tag can be used to specify the character encoding of the source files
# that doxygen parses. Internally doxygen uses the UTF-8 encoding, which is

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libraries/BitBangI2C/BitBangI2C.cpp Normal file
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/*
* Copyright (C) 2012 Southern Storm Software, Pty Ltd.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include "BitBangI2C.h"
#include <WProgram.h>
/**
* \class BitBangI2C BitBangI2C.h <BitBangI2C.h>
* \brief Bit-banged implementation of an I2C master.
*
* This class implements the I2C master protocol on any arbitrary pair
* of data and clock pins. It is not restricted to pre-defined pins as
* is the case for the standard \c Wire library.
*
* This implementation only implements the master side of the protocol.
* It assumes that there is a single bus master, no arbitration, and
* no clock stretching.
*/
#define i2cDelay() delayMicroseconds(5)
/**
* \brief Constructs a new bit-banged I2C master on \a dataPin and \a clockPin.
*/
BitBangI2C::BitBangI2C(uint8_t dataPin, uint8_t clockPin)
: _dataPin(dataPin)
, _clockPin(clockPin)
, started(false)
{
// Initially set the CLOCK and DATA lines to be outputs in the high state.
pinMode(_clockPin, OUTPUT);
pinMode(_dataPin, OUTPUT);
digitalWrite(_clockPin, HIGH);
digitalWrite(_dataPin, HIGH);
}
/**
* \typedef BitBangI2C::ack_t
* \brief Type that represents an I2C ACK or NACK indication.
*/
/**
* \var BitBangI2C::ACK
* \brief Indicates that an I2C operation was acknowledged.
*/
/**
* \var BitBangI2C::NACK
* \brief Indicates that an I2C operation was not acknowledged.
*/
/**
* \brief Transmits an I2C start condition on the bus.
*
* \sa startRead(), startWrite()
*/
void BitBangI2C::start()
{
pinMode(_dataPin, OUTPUT);
if (started) {
// Already started, so send a restart condition.
digitalWrite(_dataPin, HIGH);
digitalWrite(_clockPin, HIGH);
i2cDelay();
}
digitalWrite(_dataPin, LOW);
i2cDelay();
digitalWrite(_clockPin, LOW);
i2cDelay();
started = true;
}
/**
* \brief Transmits an I2C stop condition on the bus.
*/
void BitBangI2C::stop()
{
pinMode(_dataPin, OUTPUT);
digitalWrite(_dataPin, LOW);
digitalWrite(_clockPin, HIGH);
i2cDelay();
digitalWrite(_dataPin, HIGH);
i2cDelay();
started = false;
}
#define I2C_WRITE 0x00
#define I2C_WRITE10 0xF0
#define I2C_READ 0x01
#define I2C_READ10 0xF1
/**
* \brief Starts a write operation by sending a start condition and the I2C control byte.
*
* The \a address must be the 7-bit or 10-bit address of the I2C slave
* on the bus.
*
* Returns BitBangI2C::ACK or BitBangI2C::NACK to indicate whether the
* read operation was acknowledged by the slave or not.
*
* \sa startWrite()
*/
BitBangI2C::ack_t BitBangI2C::startWrite(unsigned int address)
{
start();
if (address < 0x80) {
// 7-bit address.
return write((uint8_t)((address << 1) | I2C_WRITE));
} else {
// 10-bit address.
if (write((uint8_t)(((address >> 7) & 0x06)) | I2C_WRITE10) == NACK)
return NACK;
return write((uint8_t)address);
}
}
/**
* \brief Starts a read operation by sending the start condition and the I2C control byte.
*
* The \a address must be the 7-bit or 10-bit address of the I2C slave
* on the bus.
*
* Returns BitBangI2C::ACK or BitBangI2C::NACK to indicate whether the
* read operation was acknowledged by the slave or not.
*
* \sa startWrite()
*/
BitBangI2C::ack_t BitBangI2C::startRead(unsigned int address)
{
start();
if (address < 0x80) {
// 7-bit address.
return write((uint8_t)((address << 1) | I2C_READ));
} else {
// 10-bit address.
if (write((uint8_t)(((address >> 7) & 0x06)) | I2C_READ10) == NACK)
return NACK;
return write((uint8_t)address);
}
}
/**
* \brief Writes a single byte \a value on the I2C bus.
*
* Returns BitBangI2C::ACK or BitBangI2C::NACK to indicate whether the
* slave acknowledged the byte or not.
*/
BitBangI2C::ack_t BitBangI2C::write(uint8_t value)
{
uint8_t mask = 0x80;
while (mask != 0) {
writeBit((value & mask) != 0);
mask >>= 1;
}
return readBit();
}
/**
* \brief Reads a single byte from the I2C bus.
*
* If \a ack is BitBangI2C::ACK, then the byte is acknowledged. Otherwise
* the byte will not be acknowledged.
*/
uint8_t BitBangI2C::read(ack_t ack)
{
uint8_t value = 0;
for (uint8_t bit = 0; bit < 8; ++bit)
value = (value << 1) | readBit();
writeBit(ack);
return value;
}
void BitBangI2C::writeBit(bool bit)
{
pinMode(_dataPin, OUTPUT);
if (bit)
digitalWrite(_dataPin, HIGH);
else
digitalWrite(_dataPin, LOW);
i2cDelay();
digitalWrite(_clockPin, HIGH);
i2cDelay();
digitalWrite(_clockPin, LOW);
i2cDelay();
}
bool BitBangI2C::readBit()
{
pinMode(_dataPin, INPUT);
digitalWrite(_dataPin, HIGH);
digitalWrite(_clockPin, HIGH);
bool bit = digitalRead(_dataPin);
i2cDelay();
digitalWrite(_clockPin, LOW);
i2cDelay();
return bit;
}

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libraries/BitBangI2C/BitBangI2C.h Normal file
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/*
* Copyright (C) 2012 Southern Storm Software, Pty Ltd.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#ifndef BitBangI2C_h
#define BitBangI2C_h
#include <inttypes.h>
class BitBangI2C {
public:
BitBangI2C(uint8_t dataPin, uint8_t clockPin);
typedef bool ack_t;
static const ack_t ACK = false;
static const ack_t NACK = true;
void start();
void stop();
ack_t startWrite(unsigned int address);
ack_t startRead(unsigned int address);
ack_t write(uint8_t value);
uint8_t read(ack_t ack = ACK);
private:
uint8_t _dataPin;
uint8_t _clockPin;
bool started;
void writeBit(bool bit);
bool readBit();
};
#endif