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Wire.cpp
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executable file
·330 lines (279 loc) · 8.24 KB
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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
Modified 2012 by Todd Krein (todd@krein.org) to implement repeated starts
*/
extern "C" {
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include "utility/twi.h"
}
#include "Wire.h"
// Initialize Class Variables //////////////////////////////////////////////////
uint8_t TwoWire::rxBuffer[BUFFER_LENGTH];
uint8_t TwoWire::rxBufferIndex = 0;
uint8_t TwoWire::rxBufferLength = 0;
uint8_t TwoWire::txAddress = 0;
uint8_t TwoWire::txBuffer[BUFFER_LENGTH];
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)
{
rxBufferIndex = 0;
rxBufferLength = 0;
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::end(void)
{
twi_disable();
}
void TwoWire::setClock(uint32_t clock)
{
twi_setFrequency(clock);
}
uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity, uint32_t iaddress, uint8_t isize, uint8_t sendStop)
{
if (isize > 0) {
// send internal address; this mode allows sending a repeated start to access
// some devices' internal registers. This function is executed by the hardware
// TWI module on other processors (for example Due's TWI_IADR and TWI_MMR registers)
beginTransmission(address);
// the maximum size of internal address is 3 bytes
if (isize > 3){
isize = 3;
}
// write internal register address - most significant byte first
while (isize-- > 0)
write((uint8_t)(iaddress >> (isize*8)));
endTransmission(false);
}
// clamp to buffer length
if(quantity > BUFFER_LENGTH){
quantity = BUFFER_LENGTH;
}
// perform blocking read into buffer
uint8_t read = twi_readFrom(address, rxBuffer, quantity, sendStop);
// set rx buffer iterator vars
rxBufferIndex = 0;
rxBufferLength = read;
return read;
}
uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity, uint8_t sendStop) {
return requestFrom((uint8_t)address, (uint8_t)quantity, (uint32_t)0, (uint8_t)0, (uint8_t)sendStop);
}
uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity)
{
return requestFrom((uint8_t)address, (uint8_t)quantity, (uint8_t)true);
}
uint8_t TwoWire::requestFrom(int address, int quantity)
{
return requestFrom((uint8_t)address, (uint8_t)quantity, (uint8_t)true);
}
uint8_t TwoWire::requestFrom(int address, int quantity, int sendStop)
{
return requestFrom((uint8_t)address, (uint8_t)quantity, (uint8_t)sendStop);
}
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);
}
//
// Originally, 'endTransmission' was an f(void) function.
// It has been modified to take one parameter indicating
// whether or not a STOP should be performed on the bus.
// Calling endTransmission(false) allows a sketch to
// perform a repeated start.
//
// WARNING: Nothing in the library keeps track of whether
// the bus tenure has been properly ended with a STOP. It
// is very possible to leave the bus in a hung state if
// no call to endTransmission(true) is made. Some I2C
// devices will behave oddly if they do not see a STOP.
//
uint8_t TwoWire::endTransmission(uint8_t sendStop)
{
// transmit buffer (blocking)
uint8_t ret = twi_writeTo(txAddress, txBuffer, txBufferLength, 1, sendStop);
// reset tx buffer iterator vars
txBufferIndex = 0;
txBufferLength = 0;
// indicate that we are done transmitting
transmitting = 0;
return ret;
}
// This provides backwards compatibility with the original
// definition, and expected behaviour, of endTransmission
//
uint8_t TwoWire::endTransmission(void)
{
return endTransmission(true);
}
// must be called in:
// slave tx event callback
// or after beginTransmission(address)
size_t TwoWire::write(uint8_t data)
{
if(transmitting){
// in master transmitter mode
// don't bother if buffer is full
if(txBufferLength >= BUFFER_LENGTH){
setWriteError();
return 0;
}
// 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);
}
return 1;
}
// must be called in:
// slave tx event callback
// or after beginTransmission(address)
size_t TwoWire::write(const uint8_t *data, size_t quantity)
{
if(transmitting){
// in master transmitter mode
for(size_t i = 0; i < quantity; ++i){
write(data[i]);
}
}else{
// in slave send mode
// reply to master
twi_transmit(data, quantity);
}
return quantity;
}
// must be called in:
// slave rx event callback
// or after requestFrom(address, numBytes)
int TwoWire::available(void)
{
return rxBufferLength - rxBufferIndex;
}
// must be called in:
// slave rx event callback
// or after requestFrom(address, numBytes)
int TwoWire::read(void)
{
int value = -1;
// get each successive byte on each call
if(rxBufferIndex < rxBufferLength){
value = rxBuffer[rxBufferIndex];
++rxBufferIndex;
}
return value;
}
// must be called in:
// slave rx event callback
// or after requestFrom(address, numBytes)
int TwoWire::peek(void)
{
int value = -1;
if(rxBufferIndex < rxBufferLength){
value = rxBuffer[rxBufferIndex];
}
return value;
}
void TwoWire::flush(void)
{
// XXX: to be implemented.
}
// 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();