An arduino library to communicate using the Dallas one-wire protocol, where the Arduino takes the role of a slave.
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#include "OneWireSlave.h"
// uncomment this line to enable sending messages along with errors (but takes more program memory)
//#define ERROR_MESSAGES
#ifdef ERROR_MESSAGES
#define ERROR(msg) error_(msg)
#else
#define ERROR(msg) error_(0)
#endif
namespace
{
const unsigned long ResetMinDuration = 480;
const unsigned long ResetMaxDuration = 900;
const unsigned long PresenceWaitDuration = 30;
const unsigned long PresenceDuration = 300;
const unsigned long ReadBitSamplingTime = 25;
const unsigned long SendBitDuration = 35;
const byte ReceiveCommand = (byte)-1;
void(*timerEvent)() = 0;
}
OneWireSlave OneWire;
byte OneWireSlave::rom_[8];
byte OneWireSlave::scratchpad_[8];
Pin OneWireSlave::pin_;
byte OneWireSlave::tccr1bEnable_;
unsigned long OneWireSlave::resetStart_;
unsigned long OneWireSlave::lastReset_;
void(*OneWireSlave::receiveBitCallback_)(bool bit, bool error);
void(*OneWireSlave::bitSentCallback_)(bool error);
void(*OneWireSlave::clientReceiveCallback_)(ReceiveEvent evt, byte data);
byte OneWireSlave::receivingByte_;
byte OneWireSlave::searchRomBytePos_;
byte OneWireSlave::searchRomBitPos_;
bool OneWireSlave::searchRomInverse_;
byte* OneWireSlave::buffer_;
short OneWireSlave::bufferLength_;
byte OneWireSlave::bufferBitPos_;
short OneWireSlave::bufferPos_;
void(*OneWireSlave::receiveBytesCallback_)(bool error);
void(*OneWireSlave::sendBytesCallback_)(bool error);
ISR(TIMER1_COMPA_vect) // timer1 interrupt
{
TCCR1B = 0; // disable clock
void(*event)() = timerEvent;
timerEvent = 0;
event();
}
void OneWireSlave::begin(byte* rom, byte pinNumber)
{
pin_ = Pin(pinNumber);
resetStart_ = (unsigned long)-1;
lastReset_ = 0;
memcpy(rom_, rom, 7);
rom_[7] = crc8(rom_, 7);
// log("Enabling 1-wire library")
cli(); // disable interrupts
pin_.inputMode();
pin_.writeLow(); // make sure the internal pull-up resistor is disabled
// prepare hardware timer
TCCR1A = 0;
TCCR1B = 0;
TIMSK1 |= (1 << OCIE1A); // enable timer compare interrupt
tccr1bEnable_ = (1 << WGM12) | (1 << CS11) | (1 << CS10); // turn on CTC mode with 64 prescaler
// start 1-wire activity
beginWaitReset_();
sei(); // enable interrupts
}
void OneWireSlave::end()
{
#ifdef DEBUG_LOG
debug.append("Disabling 1-wire library");
#endif
cli();
disableTimer_();
pin_.detachInterrupt();
releaseBus_();
sei();
}
void OneWireSlave::write(byte* bytes, short numBytes, void(*complete)(bool error))
{
cli();
beginWriteBytes_(bytes, numBytes, complete == 0 ? noOpCallback_ : complete);
sei();
}
byte OneWireSlave::crc8(byte* data, short numBytes)
{
byte crc = 0;
while (numBytes--) {
byte inbyte = *data++;
for (byte i = 8; i; i--) {
byte mix = (crc ^ inbyte) & 0x01;
crc >>= 1;
if (mix) crc ^= 0x8C;
inbyte >>= 1;
}
}
return crc;
}
void OneWireSlave::setTimerEvent_(short delayMicroSeconds, void(*handler)())
{
delayMicroSeconds -= 10; // remove overhead (tuned on Arduino Uno)
short skipTicks = (delayMicroSeconds - 3) / 4; // round the micro seconds delay to a number of ticks to skip (4us per tick, so 4us must skip 0 tick, 8us must skip 1 tick, etc.)
if (skipTicks < 1) skipTicks = 1;
TCNT1 = 0;
OCR1A = skipTicks;
timerEvent = handler;
TCCR1B = tccr1bEnable_;
}
void OneWireSlave::disableTimer_()
{
TCCR1B = 0;
}
void OneWireSlave::onEnterInterrupt_()
{
#ifdef DEBUG_LOG
dbgOutput.writeLow();
#endif
}
void OneWireSlave::onLeaveInterrupt_()
{
#ifdef DEBUG_LOG
dbgOutput.writeHigh();
#endif
}
void OneWireSlave::error_(const char* message)
{
#ifdef DEBUG_LOG
if (message == 0)
debug.append("unspecified error");
else
debug.append(message);
#endif
beginWaitReset_();
}
void OneWireSlave::pullLow_()
{
pin_.outputMode();
pin_.writeLow();
}
void OneWireSlave::releaseBus_()
{
pin_.inputMode();
}
void OneWireSlave::beginResetDetection_()
{
setTimerEvent_(ResetMinDuration - 50, &OneWireSlave::resetCheck_);
resetStart_ = micros() - 50;
}
void OneWireSlave::cancelResetDetection_()
{
disableTimer_();
resetStart_ = (unsigned long)-1;
}
void OneWireSlave::resetCheck_()
{
onEnterInterrupt_();
if (!pin_.read())
{
pin_.attachInterrupt(&OneWireSlave::waitReset_, CHANGE);
// log("Reset detected during another operation");
}
onLeaveInterrupt_();
}
void OneWireSlave::beginReceiveBit_(void(*completeCallback)(bool bit, bool error))
{
receiveBitCallback_ = completeCallback;
pin_.attachInterrupt(&OneWireSlave::receive_, FALLING);
}
void OneWireSlave::receive_()
{
onEnterInterrupt_();
pin_.detachInterrupt();
setTimerEvent_(ReadBitSamplingTime, &OneWireSlave::readBit_);
onLeaveInterrupt_();
}
void OneWireSlave::readBit_()
{
onEnterInterrupt_();
bool bit = pin_.read();
if (bit)
cancelResetDetection_();
else
beginResetDetection_();
receiveBitCallback_(bit, false);
//dbgOutput.writeLow();
//dbgOutput.writeHigh();
onLeaveInterrupt_();
}
void OneWireSlave::beginSendBit_(bool bit, void(*completeCallback)(bool error))
{
bitSentCallback_ = completeCallback;
if (bit)
{
pin_.attachInterrupt(&OneWireSlave::sendBitOne_, FALLING);
}
else
{
pin_.attachInterrupt(&OneWireSlave::sendBitZero_, FALLING);
}
}
void OneWireSlave::sendBitOne_()
{
onEnterInterrupt_();
beginResetDetection_();
bitSentCallback_(false);
onLeaveInterrupt_();
}
void OneWireSlave::sendBitZero_()
{
pullLow_(); // this must be executed first because the timing is very tight with some master devices
onEnterInterrupt_();
pin_.detachInterrupt();
setTimerEvent_(SendBitDuration, &OneWireSlave::endSendBitZero_);
onLeaveInterrupt_();
}
void OneWireSlave::endSendBitZero_()
{
onEnterInterrupt_();
releaseBus_();
bitSentCallback_(false);
onLeaveInterrupt_();
}
void OneWireSlave::beginWaitReset_()
{
disableTimer_();
pin_.attachInterrupt(&OneWireSlave::waitReset_, CHANGE);
resetStart_ = (unsigned int)-1;
}
void OneWireSlave::waitReset_()
{
onEnterInterrupt_();
bool state = pin_.read();
unsigned long now = micros();
if (state)
{
if (resetStart_ == (unsigned int)-1)
{
onLeaveInterrupt_();
return;
}
unsigned long resetDuration = now - resetStart_;
resetStart_ = (unsigned int)-1;
if (resetDuration >= ResetMinDuration)
{
if (resetDuration > ResetMaxDuration)
{
ERROR("Reset too long");
onLeaveInterrupt_();
return;
}
lastReset_ = now;
pin_.detachInterrupt();
setTimerEvent_(PresenceWaitDuration - (micros() - now), &OneWireSlave::beginPresence_);
if (clientReceiveCallback_ != 0)
clientReceiveCallback_(RE_Reset, 0);
}
}
else
{
resetStart_ = now;
}
onLeaveInterrupt_();
}
void OneWireSlave::beginPresence_()
{
pullLow_();
setTimerEvent_(PresenceDuration, &OneWireSlave::endPresence_);
}
void OneWireSlave::endPresence_()
{
releaseBus_();
beginWaitCommand_();
}
void OneWireSlave::beginWaitCommand_()
{
bufferPos_ = ReceiveCommand;
beginReceive_();
}
void OneWireSlave::beginReceive_()
{
receivingByte_ = 0;
bufferBitPos_ = 0;
beginReceiveBit_(&OneWireSlave::onBitReceived_);
}
void OneWireSlave::onBitReceived_(bool bit, bool error)
{
if (error)
{
ERROR("Invalid bit");
if (bufferPos_ >= 0)
receiveBytesCallback_(true);
return;
}
receivingByte_ |= ((bit ? 1 : 0) << bufferBitPos_);
++bufferBitPos_;
if (bufferBitPos_ == 8)
{
// log("received byte", (long)receivingByte_);
if (bufferPos_ == ReceiveCommand)
{
bufferPos_ = 0;
switch (receivingByte_)
{
case 0xF0: // SEARCH ROM
beginSearchRom_();
return;
case 0x33: // READ ROM
beginWriteBytes_(rom_, 8, &OneWireSlave::noOpCallback_);
return;
case 0x55: // MATCH ROM
beginReceiveBytes_(scratchpad_, 8, &OneWireSlave::matchRomBytesReceived_);
return;
case 0xCC: // SKIP ROM
// emulate a match rom operation
memcpy(scratchpad_, rom_, 8);
matchRomBytesReceived_(false);
return;
default:
ERROR("Unknown command");
return;
}
}
else
{
buffer_[bufferPos_++] = receivingByte_;
receivingByte_ = 0;
bufferBitPos_ = 0;
if (bufferPos_ == bufferLength_)
{
beginWaitReset_();
receiveBytesCallback_(false);
return;
}
}
}
beginReceiveBit_(&OneWireSlave::onBitReceived_);
}
void OneWireSlave::beginSearchRom_()
{
searchRomBytePos_ = 0;
searchRomBitPos_ = 0;
searchRomInverse_ = false;
beginSearchRomSendBit_();
}
void OneWireSlave::beginSearchRomSendBit_()
{
byte currentByte = rom_[searchRomBytePos_];
bool currentBit = bitRead(currentByte, searchRomBitPos_);
bool bitToSend = searchRomInverse_ ? !currentBit : currentBit;
beginSendBit_(bitToSend, &OneWireSlave::continueSearchRom_);
}
void OneWireSlave::continueSearchRom_(bool error)
{
if (error)
{
ERROR("Failed to send bit");
return;
}
searchRomInverse_ = !searchRomInverse_;
if (searchRomInverse_)
{
beginSearchRomSendBit_();
}
else
{
beginReceiveBit_(&OneWireSlave::searchRomOnBitReceived_);
}
}
void OneWireSlave::searchRomOnBitReceived_(bool bit, bool error)
{
if (error)
{
ERROR("Bit read error during ROM search");
return;
}
byte currentByte = rom_[searchRomBytePos_];
bool currentBit = bitRead(currentByte, searchRomBitPos_);
if (bit == currentBit)
{
++searchRomBitPos_;
if (searchRomBitPos_ == 8)
{
searchRomBitPos_ = 0;
++searchRomBytePos_;
}
if (searchRomBytePos_ == 8)
{
// log("ROM sent entirely");
beginWaitReset_();
}
else
{
beginSearchRomSendBit_();
}
}
else
{
// log("Leaving ROM search");
beginWaitReset_();
}
}
void OneWireSlave::beginWriteBytes_(byte* data, short numBytes, void(*complete)(bool error))
{
buffer_ = data;
bufferLength_ = numBytes;
bufferPos_ = 0;
bufferBitPos_ = 0;
sendBytesCallback_ = complete;
bool bit = bitRead(buffer_[0], 0);
beginSendBit_(bit, &OneWireSlave::bitSent_);
}
void OneWireSlave::bitSent_(bool error)
{
if (error)
{
ERROR("error sending a bit");
sendBytesCallback_(true);
return;
}
++bufferBitPos_;
if (bufferBitPos_ == 8)
{
bufferBitPos_ = 0;
++bufferPos_;
}
if (bufferPos_ == bufferLength_)
{
beginWaitReset_();
sendBytesCallback_(false);
return;
}
bool bit = bitRead(buffer_[bufferPos_], bufferBitPos_);
beginSendBit_(bit, &OneWireSlave::bitSent_);
}
void OneWireSlave::beginReceiveBytes_(byte* buffer, short numBytes, void(*complete)(bool error))
{
buffer_ = buffer;
bufferLength_ = numBytes;
bufferPos_ = 0;
receiveBytesCallback_ = complete;
beginReceive_();
}
void OneWireSlave::noOpCallback_(bool error)
{
if (error)
ERROR("error during an internal 1-wire operation");
}
void OneWireSlave::matchRomBytesReceived_(bool error)
{
if (error)
{
ERROR("error receiving match rom bytes");
return;
}
if (memcmp(rom_, scratchpad_, 8) == 0)
{
// log("ROM matched");
beginReceiveBytes_(scratchpad_, 1, &OneWireSlave::notifyClientByteReceived_);
}
else
{
// log("ROM not matched");
beginWaitReset_();
}
}
void OneWireSlave::notifyClientByteReceived_(bool error)
{
if (error)
{
if (clientReceiveCallback_ != 0)
clientReceiveCallback_(RE_Error, 0);
ERROR("error receiving custom bytes");
return;
}
beginReceiveBytes_(scratchpad_, 1, &OneWireSlave::notifyClientByteReceived_);
if (clientReceiveCallback_ != 0)
clientReceiveCallback_(RE_Byte, scratchpad_[0]);
}