library - Wire

ArduinoAddons/Arduino_1.6.x/hardware/marlin/avr/libraries/Wire/Wire.cpp

@@ -0,0 +1,303 @@
+/*
+  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 "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::setClock(uint32_t frequency)
+{
+  TWBR = ((F_CPU / frequency) - 16) / 2;
+}
+
+uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity, uint8_t sendStop)
+{
+  // 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)
+{
+  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)
+  int8_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();
+