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Arduino/hardware/libraries/Wire/Wire.cpp

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/*
TwoWire.cpp - TWI/I2C library for Wiring & Arduino
Copyright (c) 2006 Nicholas Zambetti. All right reserved.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
extern "C" {
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include "twi.h"
}
#include "Wire.h"
// Initialize Class Variables //////////////////////////////////////////////////
uint8_t* TwoWire::rxBuffer = 0;
uint8_t TwoWire::rxBufferIndex = 0;
uint8_t TwoWire::rxBufferLength = 0;
uint8_t TwoWire::txAddress = 0;
uint8_t* TwoWire::txBuffer = 0;
uint8_t TwoWire::txBufferIndex = 0;
uint8_t TwoWire::txBufferLength = 0;
uint8_t TwoWire::transmitting = 0;
void (*TwoWire::user_onRequest)(void);
void (*TwoWire::user_onReceive)(int);
// Constructors ////////////////////////////////////////////////////////////////
TwoWire::TwoWire()
{
}
// Public Methods //////////////////////////////////////////////////////////////
void TwoWire::begin(void)
{
// init buffer for reads
rxBuffer = (uint8_t*) calloc(BUFFER_LENGTH, sizeof(uint8_t));
rxBufferIndex = 0;
rxBufferLength = 0;
// init buffer for writes
txBuffer = (uint8_t*) calloc(BUFFER_LENGTH, sizeof(uint8_t));
txBufferIndex = 0;
txBufferLength = 0;
twi_init();
}
void TwoWire::begin(uint8_t address)
{
twi_setAddress(address);
twi_attachSlaveTxEvent(onRequestService);
twi_attachSlaveRxEvent(onReceiveService);
begin();
}
void TwoWire::begin(int address)
{
begin((uint8_t)address);
}
void TwoWire::requestFrom(uint8_t address, uint8_t quantity)
{
// clamp to buffer length
if(quantity > BUFFER_LENGTH){
quantity = BUFFER_LENGTH;
}
// perform blocking read into buffer
twi_readFrom(address, rxBuffer, quantity);
// set rx buffer iterator vars
rxBufferIndex = 0;
rxBufferLength = quantity;
}
void TwoWire::requestFrom(int address, int quantity)
{
requestFrom((uint8_t)address, (uint8_t)quantity);
}
void TwoWire::beginTransmission(uint8_t address)
{
// indicate that we are transmitting
transmitting = 1;
// set address of targeted slave
txAddress = address;
// reset tx buffer iterator vars
txBufferIndex = 0;
txBufferLength = 0;
}
void TwoWire::beginTransmission(int address)
{
beginTransmission((uint8_t)address);
}
void TwoWire::endTransmission(void)
{
// transmit buffer (blocking)
twi_writeTo(txAddress, txBuffer, txBufferLength, 1);
// reset tx buffer iterator vars
txBufferIndex = 0;
txBufferLength = 0;
// indicate that we are done transmitting
transmitting = 0;
}
// must be called in:
// slave tx event callback
// or after beginTransmission(address)
void TwoWire::send(uint8_t data)
{
if(transmitting){
// in master transmitter mode
// don't bother if buffer is full
if(txBufferLength >= BUFFER_LENGTH){
return;
}
// put byte in tx buffer
txBuffer[txBufferIndex] = data;
++txBufferIndex;
// update amount in buffer
txBufferLength = txBufferIndex;
}else{
// in slave send mode
// reply to master
twi_transmit(&data, 1);
}
}
// must be called in:
// slave tx event callback
// or after beginTransmission(address)
void TwoWire::send(uint8_t* data, uint8_t quantity)
{
if(transmitting){
// in master transmitter mode
for(uint8_t i = 0; i < quantity; ++i){
send(data[i]);
}
}else{
// in slave send mode
// reply to master
twi_transmit(data, quantity);
}
}
// must be called in:
// slave tx event callback
// or after beginTransmission(address)
void TwoWire::send(char* data)
{
send((uint8_t*)data, strlen(data));
}
// must be called in:
// slave tx event callback
// or after beginTransmission(address)
void TwoWire::send(int data)
{
send((uint8_t)data);
}
// must be called in:
// slave rx event callback
// or after requestFrom(address, numBytes)
uint8_t TwoWire::available(void)
{
return rxBufferLength - rxBufferIndex;
}
// must be called in:
// slave rx event callback
// or after requestFrom(address, numBytes)
uint8_t TwoWire::receive(void)
{
// default to returning null char
// for people using with char strings
uint8_t value = '\0';
// get each successive byte on each call
if(rxBufferIndex < rxBufferLength){
value = rxBuffer[rxBufferIndex];
++rxBufferIndex;
}
return value;
}
// behind the scenes function that is called when data is received
void TwoWire::onReceiveService(uint8_t* inBytes, int numBytes)
{
// don't bother if user hasn't registered a callback
if(!user_onReceive){
return;
}
// don't bother if rx buffer is in use by a master requestFrom() op
// i know this drops data, but it allows for slight stupidity
// meaning, they may not have read all the master requestFrom() data yet
if(rxBufferIndex < rxBufferLength){
return;
}
// copy twi rx buffer into local read buffer
// this enables new reads to happen in parallel
for(uint8_t i = 0; i < numBytes; ++i){
rxBuffer[i] = inBytes[i];
}
// set rx iterator vars
rxBufferIndex = 0;
rxBufferLength = numBytes;
// alert user program
user_onReceive(numBytes);
}
// behind the scenes function that is called when data is requested
void TwoWire::onRequestService(void)
{
// don't bother if user hasn't registered a callback
if(!user_onRequest){
return;
}
// reset tx buffer iterator vars
// !!! this will kill any pending pre-master sendTo() activity
txBufferIndex = 0;
txBufferLength = 0;
// alert user program
user_onRequest();
}
// sets function called on slave write
void TwoWire::onReceive( void (*function)(int) )
{
user_onReceive = function;
}
// sets function called on slave read
void TwoWire::onRequest( void (*function)(void) )
{
user_onRequest = function;
}
// Preinstantiate Objects //////////////////////////////////////////////////////
TwoWire Wire = TwoWire();