Include custom Wire lib

lib/Wire/Wire.cpp

@@ -0,0 +1,378 @@
+/*
+  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
+  Modified 2017 by Chuck Todd (ctodd@cableone.net) to correct Unconfigured Slave Mode reboot
+  Modified 2020 by Greyson Christoforo (grey@christoforo.net) to implement timeouts
+*/
+
+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();
+  twi_attachSlaveTxEvent(onRequestService); // default callback must exist
+  twi_attachSlaveRxEvent(onReceiveService); // default callback must exist
+}
+
+void TwoWire::begin(uint8_t address)
+{
+  begin();
+  twi_setAddress(address);
+}
+
+void TwoWire::begin(int address)
+{
+  begin((uint8_t)address);
+}
+
+void TwoWire::end(void)
+{
+  twi_disable();
+}
+
+void TwoWire::setClock(uint32_t clock)
+{
+  twi_setFrequency(clock);
+}
+
+/***
+ * Sets the TWI timeout.
+ *
+ * This limits the maximum time to wait for the TWI hardware. If more time passes, the bus is assumed
+ * to have locked up (e.g. due to noise-induced glitches or faulty slaves) and the transaction is aborted.
+ * Optionally, the TWI hardware is also reset, which can be required to allow subsequent transactions to
+ * succeed in some cases (in particular when noise has made the TWI hardware think there is a second
+ * master that has claimed the bus).
+ *
+ * When a timeout is triggered, a flag is set that can be queried with `getWireTimeoutFlag()` and is cleared
+ * when `clearWireTimeoutFlag()` or `setWireTimeoutUs()` is called.
+ *
+ * Note that this timeout can also trigger while waiting for clock stretching or waiting for a second master
+ * to complete its transaction. So make sure to adapt the timeout to accomodate for those cases if needed.
+ * A typical timeout would be 25ms (which is the maximum clock stretching allowed by the SMBus protocol),
+ * but (much) shorter values will usually also work.
+ *
+ * In the future, a timeout will be enabled by default, so if you require the timeout to be disabled, it is
+ * recommended you disable it by default using `setWireTimeoutUs(0)`, even though that is currently
+ * the default.
+ *
+ * @param timeout a timeout value in microseconds, if zero then timeout checking is disabled
+ * @param reset_with_timeout if true then TWI interface will be automatically reset on timeout
+ *                           if false then TWI interface will not be reset on timeout
+
+ */
+void TwoWire::setWireTimeout(uint32_t timeout, bool reset_with_timeout){
+  twi_setTimeoutInMicros(timeout, reset_with_timeout);
+}
+
+/***
+ * Returns the TWI timeout flag.
+ *
+ * @return true if timeout has occured since the flag was last cleared.
+ */
+bool TwoWire::getWireTimeoutFlag(void){
+  return(twi_manageTimeoutFlag(false));
+}
+
+/***
+ * Clears the TWI timeout flag.
+ */
+void TwoWire::clearWireTimeoutFlag(void){
+  twi_manageTimeoutFlag(true);
+}
+
+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();
+

lib/Wire/Wire.h

@@ -0,0 +1,89 @@
+/*
+  TwoWire.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
+  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
+  Modified 2020 by Greyson Christoforo (grey@christoforo.net) to implement timeouts
+*/
+
+#ifndef TwoWire_h
+#define TwoWire_h
+
+#include <inttypes.h>
+#include "Stream.h"
+
+#define BUFFER_LENGTH 128
+
+// 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;
+
+    static uint8_t transmitting;
+    static void (*user_onRequest)(void);
+    static void (*user_onReceive)(int);
+    static void onRequestService(void);
+    static void onReceiveService(uint8_t*, int);
+  public:
+    TwoWire();
+    void begin();
+    void begin(uint8_t);
+    void begin(int);
+    void end();
+    void setClock(uint32_t);
+    void setWireTimeout(uint32_t timeout = 25000, bool reset_with_timeout = false);
+    bool getWireTimeoutFlag(void);
+    void clearWireTimeoutFlag(void);
+    void beginTransmission(uint8_t);
+    void beginTransmission(int);
+    uint8_t endTransmission(void);
+    uint8_t endTransmission(uint8_t);
+    uint8_t requestFrom(uint8_t, uint8_t);
+    uint8_t requestFrom(uint8_t, uint8_t, uint8_t);
+    uint8_t requestFrom(uint8_t, uint8_t, uint32_t, uint8_t, uint8_t);
+    uint8_t requestFrom(int, int);
+    uint8_t requestFrom(int, int, int);
+    virtual size_t write(uint8_t);
+    virtual size_t write(const uint8_t *, size_t);
+    virtual int available(void);
+    virtual int read(void);
+    virtual int peek(void);
+    virtual void flush(void);
+    void onReceive( void (*)(int) );
+    void onRequest( void (*)(void) );
+
+    inline size_t write(unsigned long n) { return write((uint8_t)n); }
+    inline size_t write(long n) { return write((uint8_t)n); }
+    inline size_t write(unsigned int n) { return write((uint8_t)n); }
+    inline size_t write(int n) { return write((uint8_t)n); }
+    using Print::write;
+};
+
+extern TwoWire Wire;
+
+#endif
+

lib/Wire/utility/twi.c

@@ -0,0 +1,666 @@
+/*
+  twi.c - 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
+  Modified 2020 by Greyson Christoforo (grey@christoforo.net) to implement timeouts
+*/
+
+#include <math.h>
+#include <stdlib.h>
+#include <inttypes.h>
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+#include <compat/twi.h>
+#include "Arduino.h" // for digitalWrite and micros
+
+#ifndef cbi
+#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
+#endif
+
+#ifndef sbi
+#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
+#endif
+
+#include "pins_arduino.h"
+#include "twi.h"
+
+static volatile uint8_t twi_state;
+static volatile uint8_t twi_slarw;
+static volatile uint8_t twi_sendStop;			// should the transaction end with a stop
+static volatile uint8_t twi_inRepStart;			// in the middle of a repeated start
+
+// twi_timeout_us > 0 prevents the code from getting stuck in various while loops here
+// if twi_timeout_us == 0 then timeout checking is disabled (the previous Wire lib behavior)
+// at some point in the future, the default twi_timeout_us value could become 25000
+// and twi_do_reset_on_timeout could become true
+// to conform to the SMBus standard
+// http://smbus.org/specs/SMBus_3_1_20180319.pdf
+static volatile uint32_t twi_timeout_us = 0ul;
+static volatile bool twi_timed_out_flag = false;  // a timeout has been seen
+static volatile bool twi_do_reset_on_timeout = false;  // reset the TWI registers on timeout
+
+static void (*twi_onSlaveTransmit)(void);
+static void (*twi_onSlaveReceive)(uint8_t*, int);
+
+static uint8_t twi_masterBuffer[TWI_BUFFER_LENGTH];
+static volatile uint8_t twi_masterBufferIndex;
+static volatile uint8_t twi_masterBufferLength;
+
+static uint8_t twi_txBuffer[TWI_BUFFER_LENGTH];
+static volatile uint8_t twi_txBufferIndex;
+static volatile uint8_t twi_txBufferLength;
+
+static uint8_t twi_rxBuffer[TWI_BUFFER_LENGTH];
+static volatile uint8_t twi_rxBufferIndex;
+
+static volatile uint8_t twi_error;
+
+/* 
+ * Function twi_init
+ * Desc     readys twi pins and sets twi bitrate
+ * Input    none
+ * Output   none
+ */
+void twi_init(void)
+{
+  // initialize state
+  twi_state = TWI_READY;
+  twi_sendStop = true;		// default value
+  twi_inRepStart = false;
+  
+  // activate internal pullups for twi.
+  digitalWrite(SDA, 1);
+  digitalWrite(SCL, 1);
+
+  // initialize twi prescaler and bit rate
+  cbi(TWSR, TWPS0);
+  cbi(TWSR, TWPS1);
+  TWBR = ((F_CPU / TWI_FREQ) - 16) / 2;
+
+  /* twi bit rate formula from atmega128 manual pg 204
+  SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
+  note: TWBR should be 10 or higher for master mode
+  It is 72 for a 16mhz Wiring board with 100kHz TWI */
+
+  // enable twi module, acks, and twi interrupt
+  TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA);
+}
+
+/* 
+ * Function twi_disable
+ * Desc     disables twi pins
+ * Input    none
+ * Output   none
+ */
+void twi_disable(void)
+{
+  // disable twi module, acks, and twi interrupt
+  TWCR &= ~(_BV(TWEN) | _BV(TWIE) | _BV(TWEA));
+
+  // deactivate internal pullups for twi.
+  digitalWrite(SDA, 0);
+  digitalWrite(SCL, 0);
+}
+
+/* 
+ * Function twi_slaveInit
+ * Desc     sets slave address and enables interrupt
+ * Input    none
+ * Output   none
+ */
+void twi_setAddress(uint8_t address)
+{
+  // set twi slave address (skip over TWGCE bit)
+  TWAR = address << 1;
+}
+
+/* 
+ * Function twi_setClock
+ * Desc     sets twi bit rate
+ * Input    Clock Frequency
+ * Output   none
+ */
+void twi_setFrequency(uint32_t frequency)
+{
+  TWBR = ((F_CPU / frequency) - 16) / 2;
+  
+  /* twi bit rate formula from atmega128 manual pg 204
+  SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
+  note: TWBR should be 10 or higher for master mode
+  It is 72 for a 16mhz Wiring board with 100kHz TWI */
+}
+
+/* 
+ * Function twi_readFrom
+ * Desc     attempts to become twi bus master and read a
+ *          series of bytes from a device on the bus
+ * Input    address: 7bit i2c device address
+ *          data: pointer to byte array
+ *          length: number of bytes to read into array
+ *          sendStop: Boolean indicating whether to send a stop at the end
+ * Output   number of bytes read
+ */
+uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sendStop)
+{
+  uint8_t i;
+
+  // ensure data will fit into buffer
+  if(TWI_BUFFER_LENGTH < length){
+    return 0;
+  }
+
+  // wait until twi is ready, become master receiver
+  uint32_t startMicros = micros();
+  while(TWI_READY != twi_state){
+    if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) {
+      twi_handleTimeout(twi_do_reset_on_timeout);
+      return 0;
+    }
+  }
+  twi_state = TWI_MRX;
+  twi_sendStop = sendStop;
+  // reset error state (0xFF.. no error occured)
+  twi_error = 0xFF;
+
+  // initialize buffer iteration vars
+  twi_masterBufferIndex = 0;
+  twi_masterBufferLength = length-1;  // This is not intuitive, read on...
+  // On receive, the previously configured ACK/NACK setting is transmitted in
+  // response to the received byte before the interrupt is signalled. 
+  // Therefor we must actually set NACK when the _next_ to last byte is
+  // received, causing that NACK to be sent in response to receiving the last
+  // expected byte of data.
+
+  // build sla+w, slave device address + w bit
+  twi_slarw = TW_READ;
+  twi_slarw |= address << 1;
+
+  if (true == twi_inRepStart) {
+    // if we're in the repeated start state, then we've already sent the start,
+    // (@@@ we hope), and the TWI statemachine is just waiting for the address byte.
+    // We need to remove ourselves from the repeated start state before we enable interrupts,
+    // since the ISR is ASYNC, and we could get confused if we hit the ISR before cleaning
+    // up. Also, don't enable the START interrupt. There may be one pending from the 
+    // repeated start that we sent ourselves, and that would really confuse things.
+    twi_inRepStart = false;			// remember, we're dealing with an ASYNC ISR
+    startMicros = micros();
+    do {
+      TWDR = twi_slarw;
+      if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) {
+        twi_handleTimeout(twi_do_reset_on_timeout);
+        return 0;
+      }
+    } while(TWCR & _BV(TWWC));
+    TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE);	// enable INTs, but not START
+  } else {
+    // send start condition
+    TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA);
+  }
+
+  // wait for read operation to complete
+  startMicros = micros();
+  while(TWI_MRX == twi_state){
+    if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) {
+      twi_handleTimeout(twi_do_reset_on_timeout);
+      return 0;
+    }
+  }
+
+  if (twi_masterBufferIndex < length) {
+    length = twi_masterBufferIndex;
+  }
+
+  // copy twi buffer to data
+  for(i = 0; i < length; ++i){
+    data[i] = twi_masterBuffer[i];
+  }
+
+  return length;
+}
+
+/* 
+ * Function twi_writeTo
+ * Desc     attempts to become twi bus master and write a
+ *          series of bytes to a device on the bus
+ * Input    address: 7bit i2c device address
+ *          data: pointer to byte array
+ *          length: number of bytes in array
+ *          wait: boolean indicating to wait for write or not
+ *          sendStop: boolean indicating whether or not to send a stop at the end
+ * Output   0 .. success
+ *          1 .. length to long for buffer
+ *          2 .. address send, NACK received
+ *          3 .. data send, NACK received
+ *          4 .. other twi error (lost bus arbitration, bus error, ..)
+ *          5 .. timeout
+ */
+uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait, uint8_t sendStop)
+{
+  uint8_t i;
+
+  // ensure data will fit into buffer
+  if(TWI_BUFFER_LENGTH < length){
+    return 1;
+  }
+
+  // wait until twi is ready, become master transmitter
+  uint32_t startMicros = micros();
+  while(TWI_READY != twi_state){
+    if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) {
+      twi_handleTimeout(twi_do_reset_on_timeout);
+      return (5);
+    }
+  }
+  twi_state = TWI_MTX;
+  twi_sendStop = sendStop;
+  // reset error state (0xFF.. no error occured)
+  twi_error = 0xFF;
+
+  // initialize buffer iteration vars
+  twi_masterBufferIndex = 0;
+  twi_masterBufferLength = length;
+  
+  // copy data to twi buffer
+  for(i = 0; i < length; ++i){
+    twi_masterBuffer[i] = data[i];
+  }
+  
+  // build sla+w, slave device address + w bit
+  twi_slarw = TW_WRITE;
+  twi_slarw |= address << 1;
+  
+  // if we're in a repeated start, then we've already sent the START
+  // in the ISR. Don't do it again.
+  //
+  if (true == twi_inRepStart) {
+    // if we're in the repeated start state, then we've already sent the start,
+    // (@@@ we hope), and the TWI statemachine is just waiting for the address byte.
+    // We need to remove ourselves from the repeated start state before we enable interrupts,
+    // since the ISR is ASYNC, and we could get confused if we hit the ISR before cleaning
+    // up. Also, don't enable the START interrupt. There may be one pending from the 
+    // repeated start that we sent outselves, and that would really confuse things.
+    twi_inRepStart = false;			// remember, we're dealing with an ASYNC ISR
+    startMicros = micros();
+    do {
+      TWDR = twi_slarw;
+      if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) {
+        twi_handleTimeout(twi_do_reset_on_timeout);
+        return (5);
+      }
+    } while(TWCR & _BV(TWWC));
+    TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE);	// enable INTs, but not START
+  } else {
+    // send start condition
+    TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE) | _BV(TWSTA);	// enable INTs
+  }
+
+  // wait for write operation to complete
+  startMicros = micros();
+  while(wait && (TWI_MTX == twi_state)){
+    if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) {
+      twi_handleTimeout(twi_do_reset_on_timeout);
+      return (5);
+    }
+  }
+  
+  if (twi_error == 0xFF)
+    return 0;	// success
+  else if (twi_error == TW_MT_SLA_NACK)
+    return 2;	// error: address send, nack received
+  else if (twi_error == TW_MT_DATA_NACK)
+    return 3;	// error: data send, nack received
+  else
+    return 4;	// other twi error
+}
+
+/* 
+ * Function twi_transmit
+ * Desc     fills slave tx buffer with data
+ *          must be called in slave tx event callback
+ * Input    data: pointer to byte array
+ *          length: number of bytes in array
+ * Output   1 length too long for buffer
+ *          2 not slave transmitter
+ *          0 ok
+ */
+uint8_t twi_transmit(const uint8_t* data, uint8_t length)
+{
+  uint8_t i;
+
+  // ensure data will fit into buffer
+  if(TWI_BUFFER_LENGTH < (twi_txBufferLength+length)){
+    return 1;
+  }
+  
+  // ensure we are currently a slave transmitter
+  if(TWI_STX != twi_state){
+    return 2;
+  }
+  
+  // set length and copy data into tx buffer
+  for(i = 0; i < length; ++i){
+    twi_txBuffer[twi_txBufferLength+i] = data[i];
+  }
+  twi_txBufferLength += length;
+  
+  return 0;
+}
+
+/* 
+ * Function twi_attachSlaveRxEvent
+ * Desc     sets function called before a slave read operation
+ * Input    function: callback function to use
+ * Output   none
+ */
+void twi_attachSlaveRxEvent( void (*function)(uint8_t*, int) )
+{
+  twi_onSlaveReceive = function;
+}
+
+/* 
+ * Function twi_attachSlaveTxEvent
+ * Desc     sets function called before a slave write operation
+ * Input    function: callback function to use
+ * Output   none
+ */
+void twi_attachSlaveTxEvent( void (*function)(void) )
+{
+  twi_onSlaveTransmit = function;
+}
+
+/* 
+ * Function twi_reply
+ * Desc     sends byte or readys receive line
+ * Input    ack: byte indicating to ack or to nack
+ * Output   none
+ */
+void twi_reply(uint8_t ack)
+{
+  // transmit master read ready signal, with or without ack
+  if(ack){
+    TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT) | _BV(TWEA);
+  }else{
+    TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT);
+  }
+}
+
+/* 
+ * Function twi_stop
+ * Desc     relinquishes bus master status
+ * Input    none
+ * Output   none
+ */
+void twi_stop(void)
+{
+  // send stop condition
+  TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTO);
+
+  // wait for stop condition to be exectued on bus
+  // TWINT is not set after a stop condition!
+  // We cannot use micros() from an ISR, so approximate the timeout with cycle-counted delays
+  const uint8_t us_per_loop = 8;
+  uint32_t counter = (twi_timeout_us + us_per_loop - 1)/us_per_loop; // Round up
+  while(TWCR & _BV(TWSTO)){
+    if(twi_timeout_us > 0ul){
+      if (counter > 0ul){
+        _delay_us(10);
+        counter--;
+      } else {
+        twi_handleTimeout(twi_do_reset_on_timeout);
+        return;
+      }
+    }
+  }
+
+  // update twi state
+  twi_state = TWI_READY;
+}
+
+/* 
+ * Function twi_releaseBus
+ * Desc     releases bus control
+ * Input    none
+ * Output   none
+ */
+void twi_releaseBus(void)
+{
+  // release bus
+  TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT);
+
+  // update twi state
+  twi_state = TWI_READY;
+}
+
+/* 
+ * Function twi_setTimeoutInMicros
+ * Desc     set a timeout for while loops that twi might get stuck in
+ * Input    timeout value in microseconds (0 means never time out)
+ * Input    reset_with_timeout: true causes timeout events to reset twi
+ * Output   none
+ */
+void twi_setTimeoutInMicros(uint32_t timeout, bool reset_with_timeout){
+  twi_timed_out_flag = false;
+  twi_timeout_us = timeout;
+  twi_do_reset_on_timeout = reset_with_timeout;
+}
+
+/* 
+ * Function twi_handleTimeout
+ * Desc     this gets called whenever a while loop here has lasted longer than
+ *          twi_timeout_us microseconds. always sets twi_timed_out_flag
+ * Input    reset: true causes this function to reset the twi hardware interface
+ * Output   none
+ */
+void twi_handleTimeout(bool reset){
+  twi_timed_out_flag = true;
+
+  if (reset) {
+    // remember bitrate and address settings
+    uint8_t previous_TWBR = TWBR;
+    uint8_t previous_TWAR = TWAR;
+
+    // reset the interface
+    twi_disable();
+    twi_init();
+
+    // reapply the previous register values
+    TWAR = previous_TWAR;
+    TWBR = previous_TWBR;
+  }
+}
+
+/*
+ * Function twi_manageTimeoutFlag
+ * Desc     returns true if twi has seen a timeout
+ *          optionally clears the timeout flag
+ * Input    clear_flag: true if we should reset the hardware
+ * Output   none
+ */
+bool twi_manageTimeoutFlag(bool clear_flag){
+  bool flag = twi_timed_out_flag;
+  if (clear_flag){
+    twi_timed_out_flag = false;
+  }
+  return(flag);
+}
+
+ISR(TWI_vect)
+{
+  switch(TW_STATUS){
+    // All Master
+    case TW_START:     // sent start condition
+    case TW_REP_START: // sent repeated start condition
+      // copy device address and r/w bit to output register and ack
+      TWDR = twi_slarw;
+      twi_reply(1);
+      break;
+
+    // Master Transmitter
+    case TW_MT_SLA_ACK:  // slave receiver acked address
+    case TW_MT_DATA_ACK: // slave receiver acked data
+      // if there is data to send, send it, otherwise stop 
+      if(twi_masterBufferIndex < twi_masterBufferLength){
+        // copy data to output register and ack
+        TWDR = twi_masterBuffer[twi_masterBufferIndex++];
+        twi_reply(1);
+      }else{
+        if (twi_sendStop){
+          twi_stop();
+       } else {
+         twi_inRepStart = true;	// we're gonna send the START
+         // don't enable the interrupt. We'll generate the start, but we
+         // avoid handling the interrupt until we're in the next transaction,
+         // at the point where we would normally issue the start.
+         TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ;
+         twi_state = TWI_READY;
+        }
+      }
+      break;
+    case TW_MT_SLA_NACK:  // address sent, nack received
+      twi_error = TW_MT_SLA_NACK;
+      twi_stop();
+      break;
+    case TW_MT_DATA_NACK: // data sent, nack received
+      twi_error = TW_MT_DATA_NACK;
+      twi_stop();
+      break;
+    case TW_MT_ARB_LOST: // lost bus arbitration
+      twi_error = TW_MT_ARB_LOST;
+      twi_releaseBus();
+      break;
+
+    // Master Receiver
+    case TW_MR_DATA_ACK: // data received, ack sent
+      // put byte into buffer
+      twi_masterBuffer[twi_masterBufferIndex++] = TWDR;
+      __attribute__ ((fallthrough));
+    case TW_MR_SLA_ACK:  // address sent, ack received
+      // ack if more bytes are expected, otherwise nack
+      if(twi_masterBufferIndex < twi_masterBufferLength){
+        twi_reply(1);
+      }else{
+        twi_reply(0);
+      }
+      break;
+    case TW_MR_DATA_NACK: // data received, nack sent
+      // put final byte into buffer
+      twi_masterBuffer[twi_masterBufferIndex++] = TWDR;
+      if (twi_sendStop){
+        twi_stop();
+      } else {
+        twi_inRepStart = true;	// we're gonna send the START
+        // don't enable the interrupt. We'll generate the start, but we
+        // avoid handling the interrupt until we're in the next transaction,
+        // at the point where we would normally issue the start.
+        TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ;
+        twi_state = TWI_READY;
+      }
+      break;
+    case TW_MR_SLA_NACK: // address sent, nack received
+      twi_stop();
+      break;
+    // TW_MR_ARB_LOST handled by TW_MT_ARB_LOST case
+
+    // Slave Receiver
+    case TW_SR_SLA_ACK:   // addressed, returned ack
+    case TW_SR_GCALL_ACK: // addressed generally, returned ack
+    case TW_SR_ARB_LOST_SLA_ACK:   // lost arbitration, returned ack
+    case TW_SR_ARB_LOST_GCALL_ACK: // lost arbitration, returned ack
+      // enter slave receiver mode
+      twi_state = TWI_SRX;
+      // indicate that rx buffer can be overwritten and ack
+      twi_rxBufferIndex = 0;
+      twi_reply(1);
+      break;
+    case TW_SR_DATA_ACK:       // data received, returned ack
+    case TW_SR_GCALL_DATA_ACK: // data received generally, returned ack
+      // if there is still room in the rx buffer
+      if(twi_rxBufferIndex < TWI_BUFFER_LENGTH){
+        // put byte in buffer and ack
+        twi_rxBuffer[twi_rxBufferIndex++] = TWDR;
+        twi_reply(1);
+      }else{
+        // otherwise nack
+        twi_reply(0);
+      }
+      break;
+    case TW_SR_STOP: // stop or repeated start condition received
+      // ack future responses and leave slave receiver state
+      twi_releaseBus();
+      // put a null char after data if there's room
+      if(twi_rxBufferIndex < TWI_BUFFER_LENGTH){
+        twi_rxBuffer[twi_rxBufferIndex] = '\0';
+      }
+      // callback to user defined callback
+      twi_onSlaveReceive(twi_rxBuffer, twi_rxBufferIndex);
+      // since we submit rx buffer to "wire" library, we can reset it
+      twi_rxBufferIndex = 0;
+      break;
+    case TW_SR_DATA_NACK:       // data received, returned nack
+    case TW_SR_GCALL_DATA_NACK: // data received generally, returned nack
+      // nack back at master
+      twi_reply(0);
+      break;
+    
+    // Slave Transmitter
+    case TW_ST_SLA_ACK:          // addressed, returned ack
+    case TW_ST_ARB_LOST_SLA_ACK: // arbitration lost, returned ack
+      // enter slave transmitter mode
+      twi_state = TWI_STX;
+      // ready the tx buffer index for iteration
+      twi_txBufferIndex = 0;
+      // set tx buffer length to be zero, to verify if user changes it
+      twi_txBufferLength = 0;
+      // request for txBuffer to be filled and length to be set
+      // note: user must call twi_transmit(bytes, length) to do this
+      twi_onSlaveTransmit();
+      // if they didn't change buffer & length, initialize it
+      if(0 == twi_txBufferLength){
+        twi_txBufferLength = 1;
+        twi_txBuffer[0] = 0x00;
+      }
+      __attribute__ ((fallthrough));		  
+      // transmit first byte from buffer, fall
+    case TW_ST_DATA_ACK: // byte sent, ack returned
+      // copy data to output register
+      TWDR = twi_txBuffer[twi_txBufferIndex++];
+      // if there is more to send, ack, otherwise nack
+      if(twi_txBufferIndex < twi_txBufferLength){
+        twi_reply(1);
+      }else{
+        twi_reply(0);
+      }
+      break;
+    case TW_ST_DATA_NACK: // received nack, we are done 
+    case TW_ST_LAST_DATA: // received ack, but we are done already!
+      // ack future responses
+      twi_reply(1);
+      // leave slave receiver state
+      twi_state = TWI_READY;
+      break;
+
+    // All
+    case TW_NO_INFO:   // no state information
+      break;
+    case TW_BUS_ERROR: // bus error, illegal stop/start
+      twi_error = TW_BUS_ERROR;
+      twi_stop();
+      break;
+  }
+}

lib/Wire/utility/twi.h

@@ -0,0 +1,59 @@
+/*
+  twi.h - 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 2020 by Greyson Christoforo (grey@christoforo.net) to implement timeouts
+*/
+
+#ifndef twi_h
+#define twi_h
+
+  #include <inttypes.h>
+
+  //#define ATMEGA8
+
+  #ifndef TWI_FREQ
+  #define TWI_FREQ 100000L
+  #endif
+
+  #ifndef TWI_BUFFER_LENGTH
+  #define TWI_BUFFER_LENGTH 128
+  #endif
+
+  #define TWI_READY 0
+  #define TWI_MRX   1
+  #define TWI_MTX   2
+  #define TWI_SRX   3
+  #define TWI_STX   4
+  
+  void twi_init(void);
+  void twi_disable(void);
+  void twi_setAddress(uint8_t);
+  void twi_setFrequency(uint32_t);
+  uint8_t twi_readFrom(uint8_t, uint8_t*, uint8_t, uint8_t);
+  uint8_t twi_writeTo(uint8_t, uint8_t*, uint8_t, uint8_t, uint8_t);
+  uint8_t twi_transmit(const uint8_t*, uint8_t);
+  void twi_attachSlaveRxEvent( void (*)(uint8_t*, int) );
+  void twi_attachSlaveTxEvent( void (*)(void) );
+  void twi_reply(uint8_t);
+  void twi_stop(void);
+  void twi_releaseBus(void);
+  void twi_setTimeoutInMicros(uint32_t, bool);
+  void twi_handleTimeout(bool);
+  bool twi_manageTimeoutFlag(bool);
+
+#endif

platformio.ini

@@ -12,6 +12,6 @@
 platform = atmelavr
 board = nanoatmega328
 framework = arduino
-lib_deps = 
+;lib_deps = 
-	stevemarple/AsyncDelay @ ^1.1.2
+;	stevemarple/AsyncDelay @ ^1.1.2
-	stevemarple/SoftWire @ ^2.0.4
+;	stevemarple/SoftWire @ ^2.0.4