Make Wire and twi buffers weak and allow to override by macro

SET_Wire_Buffers().

Author: dac1e

libraries/Wire/examples/master_reader_custombuffer/master_reader_custombuffer.ino

@@ -0,0 +1,59 @@
+// Wire Master Reader Custom Buffer
+
+// Demonstrates use of the Wire library with customized buffers
+// Reads data from an I2C/TWI slave device
+// Refer to the "Wire Slave Sender Custom Buffer" example for use with this
+
+// Created 31 Dec 2024
+
+// This example code is in the public domain.
+
+
+#include <Wire.h>
+#include <WireBuffer.h>
+#include "Arduino.h"
+
+// request 6 bytes from slave device #8
+constexpr size_t REQUESTED_BYTE_COUNT = 6;
+
+constexpr size_t RECEIVE_BUFFER_SIZE  = REQUESTED_BYTE_COUNT;
+constexpr size_t TRANSMIT_BUFFER_SIZE = 0; // There is no transmit in this sketch.
+
+SET_Wire_BUFFERS(RECEIVE_BUFFER_SIZE, TRANSMIT_BUFFER_SIZE,
+    true /* master buffers needed */, false /* no slave buffers needed */ );
+
+void setup() {
+  Wire.begin();        // join I2C bus (address optional for master)
+  Serial.begin(9600);  // start serial for output
+
+  // This is just for curiosity and could be removed
+  printWireBufferSize(Serial);
+}
+
+void loop() {
+  Wire.requestFrom(8, REQUESTED_BYTE_COUNT);
+
+  size_t count = 0;
+  while (Wire.available()) { // slave may send less than requested
+    ++count;
+    char c = Wire.read();    // receive a byte as character
+    Serial.print(c);         // print the character
+  }
+  if(count) {
+    Serial.println();
+  }
+  delay(500);
+}
+
+void printWireBufferSize(Stream& stream) {
+  stream.print("Wire receive buffer size is ");
+  stream.println(WireBuffer::RX_BUFFER_SIZE);
+  stream.print("Wire transmit buffer size is ");
+  stream.println(WireBuffer::TX_BUFFER_SIZE);
+  stream.print("twi_masterBuffer size is ");
+  stream.println(twiBuffer::TWI_MASTER_BUFFER_SIZE);
+  stream.print("twi_rxBuffer size is ");
+  stream.println(twiBuffer::TWI_RX_BUFFER_SIZE);
+  stream.print("twi_txBuffer size is ");
+  stream.println(twiBuffer::TWI_TX_BUFFER_SIZE);
+}

libraries/Wire/examples/master_writer_custombuffer/master_writer_custombuffer.ino

@@ -0,0 +1,56 @@
+// Wire Master Writer Custom Buffer
+
+// Demonstrates use of the Wire library with customized buffers
+// Writes data to an I2C/TWI slave device
+// Refer to the "Wire Slave Receiver Custom Buffer" example for use with this
+
+// Created 31 Dec 2024
+
+// This example code is in the public domain.
+
+
+#include <Wire.h>
+#include <WireBuffer.h>
+#include "Arduino.h"
+
+// The following text will not fit into the default buffer of 32 bytes.
+static const char text[] = "You really won't believe it, but x is ";
+
+constexpr size_t RECEIVE_BUFFER_SIZE  = 0;  // There is no receive in this sketch.
+constexpr size_t TRANSMIT_BUFFER_SIZE = 42; // Enhance the buffer to 42 characters.
+
+SET_Wire_BUFFERS(RECEIVE_BUFFER_SIZE, TRANSMIT_BUFFER_SIZE,
+    true /* master buffers needed */, false /* no slave buffers needed */ );
+
+void setup() {
+  Wire.begin(); // join I2C bus (address optional for master)
+
+  // This is just for curiosity and could be removed
+  Serial.begin(9600);   // start serial for output
+  printWireBufferSize(Serial);
+}
+
+static byte x = 0;
+
+void loop() {
+  Wire.beginTransmission(8); // transmit to device #8
+  Wire.write(text);          // sends multiple bytes
+  Wire.write(x);             // sends one byte
+  Wire.endTransmission();    // stop transmitting
+
+  x++;
+  delay(500);
+}
+
+void printWireBufferSize(Stream& stream) {
+  stream.print("Wire receive buffer size is ");
+  stream.println(WireBuffer::RX_BUFFER_SIZE);
+  stream.print("Wire transmit buffer size is ");
+  stream.println(WireBuffer::TX_BUFFER_SIZE);
+  stream.print("twi_masterBuffer size is ");
+  stream.println(twiBuffer::TWI_MASTER_BUFFER_SIZE);
+  stream.print("twi_rxBuffer size is ");
+  stream.println(twiBuffer::TWI_RX_BUFFER_SIZE);
+  stream.print("twi_txBuffer size is ");
+  stream.println(twiBuffer::TWI_TX_BUFFER_SIZE);
+}

libraries/Wire/examples/slave_receiver_custombuffer/slave_receiver_custombuffer.ino

@@ -0,0 +1,63 @@
+// Wire Slave Receiver Custom Buffer
+
+// Demonstrates use of the Wire library with customized buffers
+// Receives data as an I2C/TWI slave device
+// Refer to the "Wire Master Writer Custom Buffer" example for use with this
+
+// Created 31 Dec 2024
+
+// This example code is in the public domain.
+
+
+#include <Wire.h>
+#include <WireBuffer.h>
+#include "Arduino.h"
+
+constexpr size_t RECEIVE_BUFFER_SIZE  = 42; // Be able receive up to 42 characters in one message.
+constexpr size_t TRANSMIT_BUFFER_SIZE = 0;  // There is no transmit in this sketch.
+
+SET_Wire_BUFFERS(RECEIVE_BUFFER_SIZE, TRANSMIT_BUFFER_SIZE,
+    false /* no master buffers needed */, true /* slave buffers needed */ );
+
+void setup() {
+  Wire.begin(8);                // join I2C bus with address #8
+  Wire.onReceive(receiveEvent); // register event
+  Serial.begin(9600);           // start serial for output
+
+  // This is just for curiosity and could be removed
+  printWireBufferSize(Serial);
+}
+
+void loop() {
+  delay(100);
+}
+
+// function that executes whenever data is received from master
+// this function is registered as an event, see setup()
+//
+// Hint: This function is called within an interrupt context.
+// That means, that there must be enough space in the Serial output
+// buffer for the characters to be printed. Otherwise the
+// Serial.print() call will lock up.
+void receiveEvent(int howMany) {
+  while (1 < Wire.available()) { // loop through all but the last
+    const char c = Wire.read();  // receive byte as a character
+    Serial.print(c);             // print the character
+  }
+  const int x = Wire.read(); // receive byte as an integer
+  Serial.println(x);         // print the integer
+}
+
+void printWireBufferSize(Stream& stream) {
+  stream.print("Wire receive buffer size is ");
+  stream.println(WireBuffer::RX_BUFFER_SIZE);
+  stream.print("Wire transmit buffer size is ");
+  stream.println(WireBuffer::TX_BUFFER_SIZE);
+  stream.print("twi_masterBuffer size is ");
+  stream.println(twiBuffer::TWI_MASTER_BUFFER_SIZE);
+  stream.print("twi_rxBuffer size is ");
+  stream.println(twiBuffer::TWI_RX_BUFFER_SIZE);
+  stream.print("twi_txBuffer size is ");
+  stream.println(twiBuffer::TWI_TX_BUFFER_SIZE);
+  delay(250); // Give time to free up Serial output buffer.
+}

libraries/Wire/examples/slave_sender_custombuffer/slave_sender_custombuffer.ino

@@ -0,0 +1,55 @@
+// Wire Slave Sender Custom Buffer
+
+// Demonstrates use of the Wire library with customized buffers
+// Sends data as an I2C/TWI slave device
+// Refer to the "Wire Master Reader Custom Buffer" example for use with this
+
+// Created 31 Dec 2024
+
+// This example code is in the public domain.
+
+
+#include <Wire.h>
+#include <WireBuffer.h>
+#include "Arduino.h"
+
+static const char text[] = "hello "; // respond with message of 6 bytes
+
+constexpr size_t RECEIVE_BUFFER_SIZE  = 0; // There is no receive in this sketch.
+constexpr size_t TRANSMIT_BUFFER_SIZE = sizeof(text)-1; // Don't need a byte for the \0
+
+SET_Wire_BUFFERS(RECEIVE_BUFFER_SIZE, TRANSMIT_BUFFER_SIZE,
+    false /* no master buffers needed */, true /* slave buffers needed */ );
+
+void setup() {
+  Wire.begin(8);                // join I2C bus with address #8
+  Wire.onRequest(requestEvent); // register event
+
+  // This is just for curiosity and could be removed
+  Serial.begin(9600);
+  printWireBufferSize(Serial);
+}
+
+void loop() {
+  delay(100);
+}
+
+// function that executes whenever data is requested by master
+// this function is registered as an event, see setup()
+void requestEvent() {
+  Wire.write(text);
+  // as expected by master
+}
+
+void printWireBufferSize(Stream& stream) {
+  stream.print("Wire receive buffer size is ");
+  stream.println(WireBuffer::RX_BUFFER_SIZE);
+  stream.print("Wire transmit buffer size is ");
+  stream.println(WireBuffer::TX_BUFFER_SIZE);
+  stream.print("twi_masterBuffer size is ");
+  stream.println(twiBuffer::TWI_MASTER_BUFFER_SIZE);
+  stream.print("twi_rxBuffer size is ");
+  stream.println(twiBuffer::TWI_RX_BUFFER_SIZE);
+  stream.print("twi_txBuffer size is ");
+  stream.println(twiBuffer::TWI_TX_BUFFER_SIZE);
+}

libraries/Wire/src/Wire.cpp

@@ -1,5 +1,5 @@
 /*
-  TwoWire.cpp - TWI/I2C library for Wiring & Arduino
+  Wire.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
@@ -26,23 +26,24 @@
 #include <inttypes.h>
 #include "utility/twi.h"
 
+#include "WireBuffer.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);
 
+using namespace WireBuffer;
+
 // Constructors ////////////////////////////////////////////////////////////////
 
 TwoWire::TwoWire()
@@ -152,8 +153,8 @@ uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity, uint32_t iaddres
   }
 
   // clamp to buffer length
-  if(quantity > BUFFER_LENGTH){
-    quantity = BUFFER_LENGTH;
+  if(quantity > RX_BUFFER_SIZE){
+    quantity = RX_BUFFER_SIZE;
   }
   // perform blocking read into buffer
   uint8_t read = twi_readFrom(address, rxBuffer, quantity, sendStop);
@@ -240,7 +241,7 @@ size_t TwoWire::write(uint8_t data)
   if(transmitting){
   // in master transmitter mode
     // don't bother if buffer is full
-    if(txBufferLength >= BUFFER_LENGTH){
+    if(txBufferLength >= TX_BUFFER_SIZE){
       setWriteError();
       return 0;
     }
@@ -334,7 +335,7 @@ void TwoWire::onReceiveService(uint8_t* inBytes, int numBytes)
   // 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];    
+    rxBuffer[i] = inBytes[i];
   }
   // set rx iterator vars
   rxBufferIndex = 0;

libraries/Wire/src/Wire.h

@@ -1,5 +1,5 @@
 /*
-  TwoWire.h - TWI/I2C library for Arduino & Wiring
+  Wire.h - TWI/I2C library for Arduino & Wiring
   Copyright (c) 2006 Nicholas Zambetti.  All right reserved.
 
   This library is free software; you can redistribute it and/or
@@ -20,26 +20,24 @@
   Modified 2020 by Greyson Christoforo (grey@christoforo.net) to implement timeouts
 */
 
+#pragma once
+
 #ifndef TwoWire_h
 #define TwoWire_h
 
 #include <inttypes.h>
 #include "Stream.h"
 
-#define BUFFER_LENGTH 32
-
 // WIRE_HAS_END means Wire has end()
 #define WIRE_HAS_END 1
 
 class TwoWire : public Stream
 {
   private:
-    static uint8_t rxBuffer[];
     static uint8_t rxBufferIndex;
     static uint8_t rxBufferLength;
 
     static uint8_t txAddress;
-    static uint8_t txBuffer[];
     static uint8_t txBufferIndex;
     static uint8_t txBufferLength;
 

libraries/Wire/src/WireBuffer.cpp

@@ -0,0 +1,30 @@
+/*
+  WireBuffer.cpp - TWI/I2C library for Arduino & Wiring
+  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
+*/
+
+#include <stdint.h>
+#include <stddef.h>
+#include "WireBuffer.h"
+
+// Default buffers as weak buffers
+namespace WireBuffer {
+  extern __attribute__((weak)) const bufferSize_t TX_BUFFER_SIZE = WIRE_BUFFER_DEFAULT_SIZE;
+  extern __attribute__((weak)) const bufferSize_t RX_BUFFER_SIZE = WIRE_BUFFER_DEFAULT_SIZE;
+  __attribute__((weak))  uint8_t rxBuffer[WIRE_BUFFER_DEFAULT_SIZE];
+  __attribute__((weak)) uint8_t txBuffer[WIRE_BUFFER_DEFAULT_SIZE];
+}