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#include "SNAP.h"
#include "WConstants.h"
SNAP::SNAP()
{
//init our rx values
this->rxState = SNAP_idle;
this->rxFlags = 0;
this->rxHDB1 = 0;
this->rxHDB2 = 0;
this->rxLength = 0;
this->rxDestAddress = 0;
this->rxSourceAddress = 0;
this->rxCRC = 0;
this->rxBufferIndex = 0;
//clear our rx buffer.
for (byte i=0; i<RX_BUFFER_SIZE; i++)
this->rxBuffer[i] = 0;
//init our tx values
this->txDestAddress = 0;
this->txSourceAddress = 0;
this->txLength = 0;
this->txHDB2 = 0;
this->txCRC = 0;
//clear our tx buffer.
for (byte i=0; i<TX_BUFFER_SIZE; i++)
this->txBuffer[i] = 0;
//init our device count.
this->deviceCount = 0;
}
/*void SNAP::begin(long baud)
{
Serial.begin(baud);
}*/
void SNAP::receivePacket()
{
byte cmd;
while (Serial.available() > 0 && !this->packetReady())
{
cmd = Serial.read();
this->receiveByte(cmd);
}
}
void SNAP::receiveByte(byte c)
{
if (this->rxFlags & serialErrorBit)
{
this->receiveError();
return;
}
switch (this->rxState)
{
case SNAP_idle:
// In the idle state, we wait for a sync byte. If none is
// received, we remain in this state.
if (c == SNAP_SYNC)
{
this->rxState = SNAP_haveSync;
this->rxFlags &= ~msgAbortedBit; //clear
//this->debug();
//Serial.println("sync");
}
//pass it along anyway.
else
this->transmit(c);
break;
case SNAP_haveSync:
// In this state we are waiting for header definition bytes. First
// HDB2. We currently insist that all packets meet our expected
// format which is 1 byte destination address, 1 byte source
// address, and no protocol specific bytes. The ACK/NAK bits may
// be anything.
this->rxHDB2 = c;
if ((c & B11111100) != B01010000)
{
// Unsupported header. Drop it an reset
this->rxFlags |= serialErrorBit; //set serialError
this->rxFlags |= wrongByteErrorBit;
this->receiveError();
}
// All is well
else
{
//do we want ack?
if ((c & B00000011) == B00000001)
this->rxFlags |= ackRequestedBit; //set ackRequested-Bit
else
this->rxFlags &= ~ackRequestedBit; //clear
this->rxCRC = 0;
this->computeRxCRC(c);
this->rxState = SNAP_haveHDB2;
//this->debug();
//Serial.println("hdb2");
}
break;
case SNAP_haveHDB2:
// For HDB1, we insist on high bits are 0011 and low bits are the length
// of the payload.
this->rxHDB1 = c;
if ((c & B11110000) != B00110000)
{
this->rxFlags |= serialErrorBit; //set serialError
this->rxFlags |= wrongByteErrorBit;
this->receiveError();
}
else
{
// FIXME: This doesn't correspond to the SNAP specs since the length
// should become non-linear after 8 bytes. The original reprap code
// does the same thing though. kintel 20071120.
this->rxLength = c & 0x0f;
if (this->rxLength > RX_BUFFER_SIZE)
this->rxLength = RX_BUFFER_SIZE;
this->computeRxCRC(c);
this->rxState = SNAP_haveHDB1;
//this->debug();
//Serial.println("hdb1");
}
break;
case SNAP_haveHDB1:
// We should be reading the destination address now
if (!this->hasDevice(c))
{
//this->debug();
//Serial.print("no device:");
//Serial.println(c);
this->transmit(SNAP_SYNC);
this->transmit(this->rxHDB2);
this->transmit(this->rxHDB1);
this->transmit(c);
this->rxState = SNAP_haveDABPass;
this->rxFlags &= ~ackRequestedBit; //clear
this->rxFlags |= inTransmitMsgBit;
}
else
{
//save our address, as we may have multiple addresses on one arduino.
this->rxDestAddress = c;
this->computeRxCRC(c);
this->rxState = SNAP_haveDAB;
//this->debug();
//Serial.println("got dest");
}
break;
case SNAP_haveDAB:
// We should be reading the source address now
if (this->hasDevice(c))
{
// If we receive a packet from ourselves, that means it went
// around the ring and was never picked up, ie the device we
// sent to is off-line or unavailable.
// FIXME: Deal with this situation
this->receiveError();
}
/*
// this may not be required.... we check this flag before accepting new packets...
if (this->rxFlags & processingLockBit)
{
this->rxCRC = 0;
//we have not finished the last order, reject (send a NAK)
this->transmit(SNAP_SYNC);
this->transmit(computeRxCRC(B01010011)); //HDB2: NAK
this->transmit(computeRxCRC(B00110000)); // HDB1: 0 bytes, with 8 bit CRC
this->transmit(computeRxCRC(this->rxSourceAddress)); // Return to sender
this->transmit(computeRxCRC(this->rxDestAddress)); // From us
this->transmit(this->rxCRC); // CRC
this->rxFlags &= ~ackRequestedBit; //clear
this->rxFlags |= msgAbortedBit; //set
this->rxState = SNAP_idle;
}
*/
this->rxSourceAddress = c;
this->rxBufferIndex = 0;
this->computeRxCRC(c);
//this->debug();
//Serial.println("got source");
this->rxState = SNAP_readingData;
break;
case SNAP_readingData:
rxBuffer[rxBufferIndex] = c;
rxBufferIndex++;
this->computeRxCRC(c);
if (rxBufferIndex == this->rxLength)
this->rxState = SNAP_dataComplete;
break;
case SNAP_dataComplete:
// We should be receiving a CRC after data, and it
// should match what we have already computed
{
//this->debug();
//Serial.println("data done");
byte hdb2 = B01010000; // 1 byte addresses
if (c == this->rxCRC)
{
// All is good, so process the command. Rather than calling the
// appropriate function directly, we just set a flag to say
// something is ready for processing. Then in the main loop we
// detect this and process the command. This allows further
// comms processing (such as passing other tokens around the
// ring) while we're actioning the command.
hdb2 |= B00000010;
this->rxFlags |= processingLockBit; //set processingLockBit
}
// CRC mismatch, so we will NAK the packet
else
hdb2 |= B00000011;
// Send ACK or NAK back to source
if (this->rxFlags & ackRequestedBit)
{
this->transmit(SNAP_SYNC);
this->rxCRC = 0;
this->transmit(this->computeRxCRC(hdb2));
this->transmit(this->computeRxCRC(B00110000)); // HDB1: 0 bytes, with 8 bit CRC
this->transmit(this->computeRxCRC(this->rxSourceAddress)); // Return to sender
this->transmit(this->computeRxCRC(this->rxDestAddress)); // From us
this->transmit(this->rxCRC); // CRC
this->rxFlags &= ~ackRequestedBit; // clear
}
}
this->rxState = SNAP_idle;
break;
case SNAP_haveDABPass:
//this->debug();
//Serial.println("dab pass");
this->transmit(c); // We will be reading source addr; pass it on
// Increment data length by 1 so that we just copy the CRC
// at the end as well.
this->rxLength++;
this->rxState = SNAP_readingDataPass;
break;
case SNAP_readingDataPass:
// this->debug();
// Serial.println("data pass");
this->transmit(c); // This is a data byte; pass it on
if (this->rxLength > 1)
this->rxLength--;
else
{
//init our rx values
this->rxState = SNAP_idle;
this->rxFlags = 0;
this->rxHDB1 = 0;
this->rxHDB2 = 0;
this->rxLength = 0;
this->rxDestAddress = 0;
this->rxSourceAddress = 0;
this->rxCRC = 0;
this->rxBufferIndex = 0;
//clear our rx buffer.
for (byte i=0; i<RX_BUFFER_SIZE; i++)
this->rxBuffer[i] = 0;
}
break;
default:
//this->debug();
//Serial.println("no state!");
this->rxFlags |= serialErrorBit; //set serialError
this->rxFlags |= wrongStateErrorBit;
this->receiveError();
}
}
void SNAP::receiveError()
{
//init our rx values
this->rxState = SNAP_idle;
this->rxFlags = 0;
this->rxHDB1 = 0;
this->rxHDB2 = 0;
this->rxLength = 0;
this->rxDestAddress = 0;
this->rxSourceAddress = 0;
this->rxCRC = 0;
this->rxBufferIndex = 0;
//clear our rx buffer.
for (byte i=0; i<RX_BUFFER_SIZE; i++)
this->rxBuffer[i] = 0;
//this->debug();
//Serial.println("error");
}
void SNAP::addDevice(byte c)
{
if (this->deviceCount >= MAX_DEVICE_COUNT)
return;
this->deviceAddresses[this->deviceCount] = c;
this->deviceCount++;
}
void SNAP::startMessage(byte to, byte from)
{
//this->debug();
//Serial.println("msg start");
//initialize our addresses.
this->txDestAddress = to;
this->txSourceAddress = from;
//initalize our variables.
this->txLength = 0;
this->txHDB2 = 0;
this->txCRC = 0;
//clear our buffer.
for (byte i=0; i<TX_BUFFER_SIZE; i++)
this->txBuffer[i] = 0;
}
/*!
High level routine that queues a byte during construction of a packet.
*/
void SNAP::sendDataByte(byte c)
{
// Put byte into packet sending buffer. Don't calculated CRCs
// yet as we don't have complete information.
// Drop if trying to send too much
if (this->txLength >= TX_BUFFER_SIZE)
return;
this->txBuffer[this->txLength] = c;
this->txLength++;
}
/*
void SNAP::sendDataInt(int i)
{
this->sendDataByte(i & 0xff);
this->sendDataByte(i >> 8);
}
void SNAP::sendDataLong(long i)
{
this->sendDataByte(i & 0xff);
this->sendDataByte(i >> 8);
this->sendDataByte(i >> 16);
this->sendDataByte(i >> 24);
}
*/
/*!
Create headers and synchronously transmit the message.
*/
void SNAP::sendMessage()
{
//this->debug();
//Serial.println("sendmsg");
this->txCRC = 0;
//here is our header.
this->transmit(SNAP_SYNC);
this->transmit(this->computeTxCRC(B01010001)); // HDB2 - Request ACK
// FIXME: This doesn't correspond to the SNAP specs since the length
// should become non-linear after 8 bytes. The original reprap code
// does the same thing though. kintel 20071120.
this->transmit(this->computeTxCRC(B00110000 | this->txLength)); // HDB1
this->transmit(this->computeTxCRC(this->txDestAddress)); // Destination
this->transmit(this->computeTxCRC(this->txSourceAddress)); // Source (us)
//payload.
for (byte i=0; i<this->txLength; i++)
this->transmit(this->computeTxCRC(this->txBuffer[i]));
this->transmit(this->txCRC);
}
/*
bool SNAP::packetReady()
{
return (this->rxFlags & processingLockBit);
}
*/
/*!
Must be manually called by the main loop when the message payload
has been consumed.
*/
void SNAP::releaseLock()
{
//init our rx values
this->rxState = SNAP_idle;
this->rxFlags = 0;
this->rxHDB1 = 0;
this->rxHDB2 = 0;
this->rxLength = 0;
this->rxDestAddress = 0;
this->rxSourceAddress = 0;
this->rxCRC = 0;
this->rxBufferIndex = 0;
//clear our rx buffer.
for (byte i=0; i<RX_BUFFER_SIZE; i++)
this->rxBuffer[i] = 0;
}
bool SNAP::hasDevice(byte c)
{
for (int i=0; i<this->deviceCount; i++)
{
if (this->deviceAddresses[i] == c)
return true;
}
return false;
}
/*
void SNAP::debug()
{
Serial.print('d');
}
void SNAP::transmit(byte c)
{
Serial.print(c, BYTE);
}
*/
/*!
Incrementally adds b to crc computation and updates crc.
returns \c.
*/
byte SNAP::computeCRC(byte b, byte crc)
{
byte i = b ^ crc;
crc = 0;
if (i & 1) crc ^= 0x5e;
if (i & 2) crc ^= 0xbc;
if (i & 4) crc ^= 0x61;
if (i & 8) crc ^= 0xc2;
if (i & 0x10) crc ^= 0x9d;
if (i & 0x20) crc ^= 0x23;
if (i & 0x40) crc ^= 0x46;
if (i & 0x80) crc ^= 0x8c;
return crc;
}
/*
byte SNAP::computeRxCRC(byte b)
{
this->rxCRC = this->computeCRC(b, this->rxCRC);
return b;
}
byte SNAP::computeTxCRC(byte b)
{
this->txCRC = this->computeCRC(b, this->txCRC);
return b;
}
byte SNAP::getDestination()
{
return this->rxDestAddress;
}
byte SNAP::getByte(byte index)
{
return this->rxBuffer[index];
}
int SNAP::getInt(byte index)
{
return (this->rxBuffer[index+1] << 8) + this->rxBuffer[index];
}
*/
// Preinstantiate Objects
SNAP snap = SNAP();
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