result_t BusHandler::handleSymbol()
{
long timeout = SYN_TIMEOUT;
unsigned char sendSymbol = ESC;
bool sending = false;
BusRequest* startRequest = NULL;
// check if another symbol has to be sent and determine timeout for receive
switch (m_state)
{
case bs_noSignal:
timeout = m_generateSynInterval>0 ? m_generateSynInterval : SIGNAL_TIMEOUT;
break;
case bs_skip:
timeout = SYN_TIMEOUT;
break;
case bs_ready:
if (m_currentRequest != NULL)
setState(bs_ready, RESULT_ERR_TIMEOUT); // just to be sure an old BusRequest is cleaned up
if (m_remainLockCount == 0 && m_currentRequest == NULL) {
startRequest = m_nextRequests.next(false);
if (startRequest == NULL && m_pollInterval > 0) { // check for poll/scan
time_t now;
time(&now);
if (m_lastPoll == 0 || difftime(now, m_lastPoll) > m_pollInterval) {
Message* message = m_messages->getNextPoll();
if (message != NULL) {
m_lastPoll = now;
PollRequest* request = new PollRequest(message);
result_t ret = request->prepare(m_ownMasterAddress);
if (ret != RESULT_OK) {
logError(lf_bus, "prepare poll message: %s", getResultCode(ret));
delete request;
}
else {
startRequest = request;
m_nextRequests.add(request);
}
}
}
}
if (startRequest != NULL) { // initiate arbitration
sendSymbol = m_ownMasterAddress;
sending = true;
}
}
break;
case bs_recvCmd:
case bs_recvCmdAck:
timeout = m_slaveRecvTimeout;
break;
case bs_recvRes:
if (m_response.size() > 0 || m_slaveRecvTimeout > SYN_TIMEOUT)
timeout = m_slaveRecvTimeout;
else
timeout = SYN_TIMEOUT;
break;
case bs_recvResAck:
timeout = m_slaveRecvTimeout;
break;
case bs_sendCmd:
if (m_currentRequest != NULL) {
sendSymbol = m_currentRequest->m_master[m_nextSendPos]; // escaped command
sending = true;
}
break;
case bs_sendResAck:
if (m_currentRequest != NULL) {
sendSymbol = m_responseCrcValid ? ACK : NAK;
sending = true;
}
break;
case bs_sendCmdAck:
if (m_currentRequest != NULL) {
sendSymbol = m_commandCrcValid ? ACK : NAK;
sending = true;
}
break;
case bs_sendRes:
if (m_currentRequest != NULL) {
sendSymbol = m_response[m_nextSendPos]; // escaped response
sending = true;
}
break;
case bs_sendSyn:
sendSymbol = SYN;
sending = true;
break;
}
// send symbol if necessary
result_t result;
if (sending) {
result = m_device->send(sendSymbol);
if (result == RESULT_OK)
if (m_state == bs_ready)
timeout = m_busAcquireTimeout;
else
timeout = SEND_TIMEOUT;
else {
sending = false;
timeout = SYN_TIMEOUT;
if (startRequest != NULL && m_nextRequests.remove(startRequest)) {
m_currentRequest = startRequest; // force the failed request to be notified
}
setState(bs_skip, result);
}
}
// receive next symbol (optionally check reception of sent symbol)
unsigned char recvSymbol;
result = m_device->recv(timeout, recvSymbol);
if (!sending && result == RESULT_ERR_TIMEOUT && m_generateSynInterval > 0 && timeout >= m_generateSynInterval && (m_state == bs_noSignal || m_state == bs_skip)) {
// check if acting as AUTO-SYN generator is required
result = m_device->send(SYN);
if (result == RESULT_OK) {
recvSymbol = ESC;
result = m_device->recv(SEND_TIMEOUT, recvSymbol);
if (result == RESULT_ERR_TIMEOUT) {
return setState(bs_noSignal, result);
}
if (result != RESULT_OK)
logError(lf_bus, "unable to receive sent AUTO-SYN symbol: %s", getResultCode(result));
else if (recvSymbol != SYN) {
logError(lf_bus, "received %2.2x instead of AUTO-SYN symbol", recvSymbol);
} else if (m_generateSynInterval != SYN_TIMEOUT) {
// received own AUTO-SYN symbol back again: act as AUTO-SYN generator now
m_generateSynInterval = SYN_TIMEOUT;
logNotice(lf_bus, "acting as AUTO-SYN generator");
}
}
return setState(bs_skip, result);
}
time_t now;
time(&now);
if (result != RESULT_OK) {
if ((m_generateSynInterval != SYN_TIMEOUT && difftime(now, m_lastReceive) > 1) // at least one full second has passed since last received symbol
|| m_state == bs_noSignal)
return setState(bs_noSignal, result);
return setState(bs_skip, result);
}
m_lastReceive = now;
if (recvSymbol == SYN) {
if (!sending && m_remainLockCount > 0 && m_command.size() != 1)
m_remainLockCount--;
else if (!sending && m_remainLockCount == 0 && m_command.size() == 1)
m_remainLockCount = 1; // wait for next AUTO-SYN after SYN / address / SYN (bus locked for own priority)
return setState(bs_ready, RESULT_ERR_SYN);
}
unsigned int headerLen, crcPos;
switch (m_state)
{
case bs_noSignal:
return setState(bs_skip, RESULT_OK);
case bs_skip:
return RESULT_OK;
case bs_ready:
if (startRequest != NULL && sending) {
if (!m_nextRequests.remove(startRequest)) {
// request already removed (e.g. due to timeout)
return setState(bs_skip, RESULT_ERR_TIMEOUT);
}
m_currentRequest = startRequest;
// check arbitration
if (recvSymbol == sendSymbol) { // arbitration successful
m_nextSendPos = 1;
m_repeat = false;
return setState(bs_sendCmd, RESULT_OK);
}
// arbitration lost. if same priority class found, try again after next AUTO-SYN
m_remainLockCount = isMaster(recvSymbol) ? 2 : 1; // number of SYN to wait for before next send try
if ((recvSymbol & 0x0f) != (sendSymbol & 0x0f) && m_lockCount > m_remainLockCount)
// if different priority class found, try again after N AUTO-SYN symbols (at least next AUTO-SYN)
m_remainLockCount = m_lockCount;
setState(m_state, RESULT_ERR_BUS_LOST); // try again later
}
result = m_command.push_back(recvSymbol, false); // expect no escaping for master address
if (result < RESULT_OK)
return setState(bs_skip, result);
m_repeat = false;
return setState(bs_recvCmd, RESULT_OK);
case bs_recvCmd:
headerLen = 4;
crcPos = m_command.size() > headerLen ? headerLen + 1 + m_command[headerLen] : 0xff; // header symbols are never escaped
result = m_command.push_back(recvSymbol, true, m_command.size() < crcPos);
if (result < RESULT_OK)
return setState(bs_skip, result);
if (result == RESULT_OK && crcPos != 0xff && m_command.size() == crcPos + 1) { // CRC received
unsigned char dstAddress = m_command[1];
m_commandCrcValid = m_command[headerLen + 1 + m_command[headerLen]] == m_command.getCRC(); // header symbols are never escaped
if (m_commandCrcValid) {
if (dstAddress == BROADCAST) {
receiveCompleted();
return setState(bs_skip, RESULT_OK);
}
if (m_answer
&& (dstAddress == m_ownMasterAddress || dstAddress == m_ownSlaveAddress))
return setState(bs_sendCmdAck, RESULT_OK);
return setState(bs_recvCmdAck, RESULT_OK);
}
if (dstAddress == BROADCAST)
return setState(bs_skip, RESULT_ERR_CRC);
if (m_answer
&& (dstAddress == m_ownMasterAddress || dstAddress == m_ownSlaveAddress)) {
return setState(bs_sendCmdAck, RESULT_ERR_CRC);
}
if (m_repeat)
return setState(bs_skip, RESULT_ERR_CRC);
return setState(bs_recvCmdAck, RESULT_ERR_CRC);
}
return RESULT_OK;
case bs_recvCmdAck:
if (recvSymbol == ACK) {
if (!m_commandCrcValid)
return setState(bs_skip, RESULT_ERR_ACK);
if (m_currentRequest != NULL) {
if (isMaster(m_currentRequest->m_master[1])) {
return setState(bs_sendSyn, RESULT_OK);
}
}
else if (isMaster(m_command[1])) { // header symbols are never escaped
receiveCompleted();
return setState(bs_skip, RESULT_OK);
}
m_repeat = false;
return setState(bs_recvRes, RESULT_OK);
}
if (recvSymbol == NAK) {
if (!m_repeat) {
m_repeat = true;
m_nextSendPos = 0;
m_command.clear();
if (m_currentRequest != NULL)
return setState(bs_sendCmd, RESULT_ERR_NAK, true);
return setState(bs_recvCmd, RESULT_ERR_NAK);
}
return setState(bs_skip, RESULT_ERR_NAK);
}
return setState(bs_skip, RESULT_ERR_ACK);
case bs_recvRes:
headerLen = 0;
crcPos = m_response.size() > headerLen ? headerLen + 1 + m_response[headerLen] : 0xff;
result = m_response.push_back(recvSymbol, true, m_response.size() < crcPos);
if (result < RESULT_OK)
return setState(bs_skip, result);
if (result == RESULT_OK && crcPos != 0xff && m_response.size() == crcPos + 1) { // CRC received
m_responseCrcValid = m_response[headerLen + 1 + m_response[headerLen]] == m_response.getCRC();
if (m_responseCrcValid) {
if (m_currentRequest != NULL)
return setState(bs_sendResAck, RESULT_OK);
return setState(bs_recvResAck, RESULT_OK);
}
if (m_repeat) {
if (m_currentRequest != NULL)
return setState(bs_sendSyn, RESULT_ERR_CRC);
return setState(bs_skip, RESULT_ERR_CRC);
}
if (m_currentRequest != NULL)
return setState(bs_sendResAck, RESULT_ERR_CRC);
return setState(bs_recvResAck, RESULT_ERR_CRC);
}
return RESULT_OK;
case bs_recvResAck:
if (recvSymbol == ACK) {
if (!m_responseCrcValid)
return setState(bs_skip, RESULT_ERR_ACK);
receiveCompleted();
return setState(bs_skip, RESULT_OK);
}
if (recvSymbol == NAK) {
if (!m_repeat) {
m_repeat = true;
m_response.clear();
return setState(bs_recvRes, RESULT_ERR_NAK, true);
}
return setState(bs_skip, RESULT_ERR_NAK);
}
return setState(bs_skip, RESULT_ERR_ACK);
case bs_sendCmd:
if (m_currentRequest != NULL && sending) {
if (recvSymbol == sendSymbol) {
// successfully sent
m_nextSendPos++;
if (m_nextSendPos >= m_currentRequest->m_master.size()) {
// master data completely sent
if (m_currentRequest->m_master[1] == BROADCAST)
return setState(bs_sendSyn, RESULT_OK);
m_commandCrcValid = true;
return setState(bs_recvCmdAck, RESULT_OK);
}
return RESULT_OK;
}
}
return setState(bs_skip, RESULT_ERR_INVALID_ARG);
case bs_sendResAck:
if (m_currentRequest != NULL && sending) {
if (recvSymbol == sendSymbol) {
// successfully sent
if (!m_responseCrcValid) {
if (!m_repeat) {
m_repeat = true;
m_response.clear();
return setState(bs_recvRes, RESULT_ERR_NAK, true);
}
return setState(bs_sendSyn, RESULT_ERR_ACK);
}
return setState(bs_sendSyn, RESULT_OK);
}
}
return setState(bs_skip, RESULT_ERR_INVALID_ARG);
case bs_sendCmdAck:
if (sending && m_answer) {
if (recvSymbol == sendSymbol) {
// successfully sent
if (!m_commandCrcValid) {
if (!m_repeat) {
m_repeat = true;
m_command.clear();
return setState(bs_recvCmd, RESULT_ERR_NAK, true);
}
return setState(bs_skip, RESULT_ERR_ACK);
}
if (isMaster(m_command[1]))
receiveCompleted(); // decode command and store value
return setState(bs_skip, RESULT_OK);
m_nextSendPos = 0;
m_repeat = false;
Message* message = m_messages->find(m_command);
if (message == NULL || !message->isPassive() || message->isWrite())
return setState(bs_skip, RESULT_ERR_INVALID_ARG); // don't know this request or definition has wrong direction, deny
// build response and store in m_response for sending back to requesting master
m_response.clear(true); // escape while sending response
result = message->prepareSlave(m_response);
if (result != RESULT_OK)
return setState(bs_skip, result);
return setState(bs_sendRes, RESULT_OK);
}
}
return setState(bs_skip, RESULT_ERR_INVALID_ARG);
case bs_sendRes:
if (sending && m_answer) {
if (recvSymbol == sendSymbol) {
// successfully sent
m_nextSendPos++;
if (m_nextSendPos >= m_response.size()) {
// slave data completely sent
return setState(bs_recvResAck, RESULT_OK);
}
return RESULT_OK;
}
}
return setState(bs_skip, RESULT_ERR_INVALID_ARG);
case bs_sendSyn:
if (sending) {
if (recvSymbol == sendSymbol) {
// successfully sent
return setState(bs_skip, RESULT_OK);
}
}
return setState(bs_skip, RESULT_ERR_INVALID_ARG);
}
return RESULT_OK;
}
