Implement handling for sending Modbus RTU broadcast requests

Introduces some methods to set the turnaround delay between a
Modbus broadcast message and a following Modbus message. More
details can be found in the Modbus_over_serial_line_V1.pdf spec
at page 10.

Change-Id: Iddeb7247566663facb79032135c1e4cc2434ca4f
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

6 files changed, 53 insertions, 11 deletions

diff --git a/src/serialbus/qmodbusclient.cpp b/src/serialbus/qmodbusclient.cpp
index cdd9b0b..d273a3a 100644
--- a/src/serialbus/qmodbusclient.cpp
+++ b/src/serialbus/qmodbusclient.cpp
@@ -361,7 +361,7 @@ void QModbusClientPrivate::processQueueElement(const QModbusResponse &pdu,
         return;
     }
 
-    if (element.reply->type() == QModbusReply::Raw) {
+    if (element.reply->type() != QModbusReply::Common) {
         element.reply->setFinished(true);
         return;
     }
diff --git a/src/serialbus/qmodbusreply.cpp b/src/serialbus/qmodbusreply.cpp
index c8b328f..a01a606 100644
--- a/src/serialbus/qmodbusreply.cpp
+++ b/src/serialbus/qmodbusreply.cpp
@@ -74,6 +74,9 @@ public:
     \value Common   The reply originates from a common read, write or read/write
                     request. See \l QModbusClient::sendReadRequest,
                     \l QModbusClient::sendWriteRequest and \l QModbusClient::sendReadWriteRequest
+    \value Broadcast The replay originates from a Modbus broadcast request. The
+                     \l serverAddress() will return \c 0 and the \l finished()
+                     signal will be emitted immediately.
 */
 
 /*!
diff --git a/src/serialbus/qmodbusreply.h b/src/serialbus/qmodbusreply.h
index 9b54687..ffefc89 100644
--- a/src/serialbus/qmodbusreply.h
+++ b/src/serialbus/qmodbusreply.h
@@ -53,7 +53,8 @@ class Q_SERIALBUS_EXPORT QModbusReply : public QObject
 public:
     enum ReplyType {
         Raw,
-        Common
+        Common,
+        Broadcast
     };
     Q_ENUM(ReplyType)
 
diff --git a/src/serialbus/qmodbusrtuserialmaster.cpp b/src/serialbus/qmodbusrtuserialmaster.cpp
index d11e7cc..a54b253 100644
--- a/src/serialbus/qmodbusrtuserialmaster.cpp
+++ b/src/serialbus/qmodbusrtuserialmaster.cpp
@@ -104,6 +104,33 @@ void QModbusRtuSerialMaster::setInterFrameDelay(int microseconds)
 }
 
 /*!
+    \since 5.13
+
+    Returns the amount of milliseconds for the silent interval between a Modbus
+    broadcast and a consecutive Modbus messages. The default value is set to
+    \c 100 milliseconds.
+*/
+int QModbusRtuSerialMaster::turnaroundDelay() const
+{
+    Q_D(const QModbusRtuSerialMaster);
+    return d->m_turnaroundDelay;
+}
+
+/*!
+    \since 5.13
+
+    Sets the amount of milliseconds for the silent interval between a Modbus
+    broadcast and a consecutive Modbus messages to \a turnaroundDelay.
+    Typically the turnaround delay is in the range of \c 100 to \c 200
+    milliseconds.
+*/
+void QModbusRtuSerialMaster::setTurnaroundDelay(int turnaroundDelay)
+{
+    Q_D(QModbusRtuSerialMaster);
+    d->m_turnaroundDelay = turnaroundDelay;
+}
+
+/*!
     \internal
 */
 QModbusRtuSerialMaster::QModbusRtuSerialMaster(QModbusRtuSerialMasterPrivate &dd, QObject *parent)
diff --git a/src/serialbus/qmodbusrtuserialmaster.h b/src/serialbus/qmodbusrtuserialmaster.h
index 5c607e2..87f58df 100644
--- a/src/serialbus/qmodbusrtuserialmaster.h
+++ b/src/serialbus/qmodbusrtuserialmaster.h
@@ -55,6 +55,9 @@ public:
     int interFrameDelay() const;
     void setInterFrameDelay(int microseconds);
 
+    int turnaroundDelay() const;
+    void setTurnaroundDelay(int turnaroundDelay);
+
 protected:
     QModbusRtuSerialMaster(QModbusRtuSerialMasterPrivate &dd, QObject *parent = nullptr);
 
diff --git a/src/serialbus/qmodbusrtuserialmaster_p.h b/src/serialbus/qmodbusrtuserialmaster_p.h
index a7bbb4b..9672684 100644
--- a/src/serialbus/qmodbusrtuserialmaster_p.h
+++ b/src/serialbus/qmodbusrtuserialmaster_p.h
@@ -182,7 +182,7 @@ public:
         processQueueElement(response, m_queue.dequeue());
 
         m_state = Idle;
-        scheduleNextRequest();
+        scheduleNextRequest(m_interFrameDelayMilliseconds);
     }
 
     void onAboutToClose()
@@ -215,7 +215,7 @@ public:
         }
 
         m_state = Idle;
-        scheduleNextRequest();
+        scheduleNextRequest(m_interFrameDelayMilliseconds);
     }
 
     void onBytesWritten(qint64 bytes)
@@ -230,8 +230,14 @@ public:
 
         qCDebug(QT_MODBUS) << "(RTU client) Send successful:" << current.requestPdu;
 
-        // TODO: Implement broadcast here.
-        current.m_timerId = m_responseTimer.start(m_responseTimeoutDuration);
+        if (!current.reply.isNull() && current.reply->type() == QModbusReply::Broadcast) {
+            m_state = ProcessReply;
+            processQueueElement({}, m_queue.dequeue());
+            m_state = Idle;
+            scheduleNextRequest(m_turnaroundDelay);
+        } else {
+            current.m_timerId = m_responseTimer.start(m_responseTimeoutDuration);
+        }
     }
 
     void onError(QSerialPort::SerialPortError error)
@@ -354,23 +360,24 @@ public:
     {
         Q_Q(QModbusRtuSerialMaster);
 
-        auto reply = new QModbusReply(type, serverAddress, q);
+        auto reply = new QModbusReply(serverAddress == 0 ? QModbusReply::Broadcast : type,
+            serverAddress, q);
         QueueElement element(reply, request, unit, m_numberOfRetries + 1);
         element.adu = QModbusSerialAdu::create(QModbusSerialAdu::Rtu, serverAddress, request);
         m_queue.enqueue(element);
 
-        scheduleNextRequest();
+        scheduleNextRequest(m_interFrameDelayMilliseconds);
 
         return reply;
     }
 
-    void scheduleNextRequest()
+    void scheduleNextRequest(int delay)
     {
         Q_Q(QModbusRtuSerialMaster);
 
         if (m_state == Idle && !m_queue.isEmpty()) {
             m_state = WaitingForReplay;
-            QTimer::singleShot(m_interFrameDelayMilliseconds, q, [this]() { processQueue(); });
+            QTimer::singleShot(delay, q, [this]() { processQueue(); });
         }
     }
 
@@ -386,7 +393,7 @@ public:
         if (current.reply.isNull()) {
             m_queue.dequeue();
             m_state = Idle;
-            scheduleNextRequest();
+            scheduleNextRequest(m_interFrameDelayMilliseconds);
         } else {
             current.bytesWritten = 0;
             current.numberOfRetries--;
@@ -427,6 +434,7 @@ public:
     QSerialPort *m_serialPort = nullptr;
 
     int m_interFrameDelayMilliseconds = 2; // A approximated value of 1.750 msec.
+    int m_turnaroundDelay = 100; // Recommended value is between 100 and 200 msec.
 };
 
 QT_END_NAMESPACE