/* Arduino DigitalIO Library
* Copyright (C) 2013 by William Greiman
*
* This file is part of the Arduino DigitalIO Library
*
* This Library is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This Library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with the Arduino DigitalIO Library. If not, see
* .
*/
/**
* @file
* @brief Software I2C library
*
* @defgroup softI2C Software I2C
* @details Software Two Wire Interface library.
* @{
*/
#include "SoftI2cMaster.h"
//------------------------------------------------------------------------------
/**
* Start an I2C transfer with possible continuation.
*
* @param[in] addrRW I2C slave address plus R/W bit.
* The I2C slave address is in the high seven bits
* and is ORed with on of the following:
* - I2C_READ for a read transfer.
* - I2C_WRITE for a write transfer.
* .
* @param[in,out] buf Source or destination for transfer.
* @param[in] nbytes Number of bytes to transfer (may be zero).
* @param[in] option Option for ending the transfer, one of:
* - I2C_STOP end the transfer with an I2C stop
* condition.
* - I2C_REP_START end the transfer with an I2C
* repeated start condition.
* - I2C_CONTINUE allow additional transferContinue()
* calls.
* .
* @return true for success else false.
*/
bool I2cMasterBase::transfer(uint8_t addrRW,
void *buf, size_t nbytes, uint8_t option)
{
if (_state != STATE_REP_START) {
start();
}
if (!write(addrRW)) {
_state = addrRW & I2C_READ ? STATE_RX_ADDR_NACK : STATE_TX_ADDR_NACK;
return false;
}
_state = addrRW & I2C_READ ? STATE_RX_DATA : STATE_TX_DATA;
return transferContinue(buf, nbytes, option);
}
//------------------------------------------------------------------------------
/**
* Continue an I2C transfer.
*
* @param[in,out] buf Source or destination for transfer.
* @param[in] nbytes Number of bytes to transfer (may be zero).
* @param[in] option Option for ending the transfer, one of:
* - I2C_STOP end the transfer with an I2C stop
* condition.
* - I2C_REP_START end the transfer with an I2C
* repeated start condition.
* - I2C_CONTINUE allow additional transferContinue()
* calls.
* .
* @return true for success else false.
*/
bool I2cMasterBase::transferContinue(void *buf, size_t nbytes, uint8_t option)
{
uint8_t* p = reinterpret_cast(buf);
if (_state == STATE_RX_DATA) {
for (size_t i = 0; i < nbytes; i++) {
p[i] = read(i == (nbytes - 1) && option != I2C_CONTINUE);
}
} else if (_state == STATE_TX_DATA) {
for (size_t i = 0; i < nbytes; i++) {
if (!write(p[i])) {
_state = STATE_TX_DATA_NACK;
return false;
}
}
} else {
return false;
}
if (option == I2C_STOP) {
stop();
_state = STATE_STOP;
} else if (option == I2C_REP_START) {
start();
_state = STATE_STOP;
}
return true;
}
//==============================================================================
// WARNING don't change SoftI2cMaster unless you verify the change with a scope
//------------------------------------------------------------------------------
/**
* Constructor, initialize SCL/SDA pins and set the bus high.
*
* @param[in] sdaPin The software SDA pin number.
*
* @param[in] sclPin The software SCL pin number.
*/
SoftI2cMaster::SoftI2cMaster(uint8_t sclPin, uint8_t sdaPin)
{
begin(sclPin, sdaPin);
}
//------------------------------------------------------------------------------
/**
* Initialize SCL/SDA pins and set the bus high.
*
* @param[in] sdaPin The software SDA pin number.
*
* @param[in] sclPin The software SCL pin number.
*/
void SoftI2cMaster::begin(uint8_t sclPin, uint8_t sdaPin)
{
uint8_t port;
// Get bit mask and address of scl registers.
_sclBit = digitalPinToBitMask(sclPin);
port = digitalPinToPort(sclPin);
_sclDDR = portModeRegister(port);
volatile uint8_t* sclOutReg = portOutputRegister(port);
// Get bit mask and address of sda registers.
_sdaBit = digitalPinToBitMask(sdaPin);
port = digitalPinToPort(sdaPin);
_sdaDDR = portModeRegister(port);
_sdaInReg = portInputRegister(port);
volatile uint8_t* sdaOutReg = portOutputRegister(port);
// Clear PORT bit for scl and sda.
uint8_t s = SREG;
noInterrupts();
*sclOutReg &= ~_sclBit;
*sdaOutReg &= ~_sdaBit;
SREG = s;
// Set scl and sda high.
writeScl(HIGH);
writeSda(HIGH);
}
//------------------------------------------------------------------------------
/* Read a byte and send ACK if more reads follow else NACK to terminate read.
*
* @param[in] last Set true to terminate the read else false.
*
* @return The byte read from the I2C bus.
*/
uint8_t SoftI2cMaster::read(uint8_t last)
{
uint8_t b = 0;
// Set sda to high Z mode for read.
writeSda(HIGH);
// Read a byte.
for (uint8_t i = 0; i < 8; i++) {
// Don't change this loop unless you verify the change with a scope.
b <<= 1;
sclDelay(16);
writeScl(HIGH);
sclDelay(12);
if (readSda()) {
b |= 1;
}
writeScl(LOW);
}
// send ACK or NACK
writeSda(last);
sclDelay(12);
writeScl(HIGH);
sclDelay(18);
writeScl(LOW);
writeSda(LOW);
return b;
}
//------------------------------------------------------------------------------
/* Issue a start condition. */
void SoftI2cMaster::start()
{
if (!readSda()) {
writeSda(HIGH);
writeScl(HIGH);
sclDelay(20);
}
writeSda(LOW);
sclDelay(20);
writeScl(LOW);
}
//------------------------------------------------------------------------------
/* Issue a stop condition. */
void SoftI2cMaster::stop(void)
{
writeSda(LOW);
sclDelay(20);
writeScl(HIGH);
sclDelay(20);
writeSda(HIGH);
sclDelay(20);
}
//------------------------------------------------------------------------------
/*
* Write a byte.
*
* @param[in] data The byte to send.
*
* @return The value true, 1, if the slave returned an ACK or false for NACK.
*/
bool SoftI2cMaster::write(uint8_t data)
{
// write byte
for (uint8_t m = 0X80; m != 0; m >>= 1) {
// don't change this loop unless you verify the change with a scope
writeSda(m & data);
sclDelay(8);
writeScl(HIGH);
sclDelay(18);
writeScl(LOW);
}
sclDelay(8);
// Go to sda high Z mode for input.
writeSda(HIGH);
writeScl(HIGH);
sclDelay(16);
// Get ACK or NACK.
uint8_t rtn = readSda();
// pull scl low.
writeScl(LOW);
// Pull sda low.
writeSda(LOW);
return rtn == 0;
}
/** @} */