Add API to set and retrieve the Modbus RTU inter frame delay.

Change-Id: Id09913509802c74b1a389d7a83a1136bbeccbaf6
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>

6 files changed, 135 insertions, 20 deletions

diff --git a/src/serialbus/qmodbusrtuserialmaster.cpp b/src/serialbus/qmodbusrtuserialmaster.cpp
index afdcac9..c8697cc 100644
--- a/src/serialbus/qmodbusrtuserialmaster.cpp
+++ b/src/serialbus/qmodbusrtuserialmaster.cpp
@@ -76,6 +76,38 @@ QModbusRtuSerialMaster::~QModbusRtuSerialMaster()
 }
 
 /*!
+    \since 5.7
+
+    Returns the amount of \a microseconds for the silent interval between two
+    consecutive Modbus messages.
+
+    \sa setInterFrameDelay()
+*/
+int QModbusRtuSerialMaster::interFrameDelay() const
+{
+    Q_D(const QModbusRtuSerialMaster);
+    return d->m_interFrameDelayMilliseconds * 1000;
+}
+
+/*!
+    \since 5.7
+
+    Sets the amount of \a microseconds for the silent interval between two
+    consecutive Modbus messages. By default, the class implementation will use
+    a pre-calculated value according to the Modbus specification. A active or
+    running connection is not affected by such delay changes.
+
+    \note If \a microseconds is set to -1 or \a microseconds is less than the
+    pre-calculated delay then this pre-calculated value is used as frame delay.
+*/
+void QModbusRtuSerialMaster::setInterFrameDelay(int microseconds)
+{
+    Q_D(QModbusRtuSerialMaster);
+    d->m_interFrameDelayMilliseconds = qCeil(qreal(microseconds) / 1000.);
+    d->calculateInterFrameDelay();
+}
+
+/*!
     \internal
 */
 QModbusRtuSerialMaster::QModbusRtuSerialMaster(QModbusRtuSerialMasterPrivate &dd, QObject *parent)
diff --git a/src/serialbus/qmodbusrtuserialmaster.h b/src/serialbus/qmodbusrtuserialmaster.h
index 7f879f5..ebdf21f 100644
--- a/src/serialbus/qmodbusrtuserialmaster.h
+++ b/src/serialbus/qmodbusrtuserialmaster.h
@@ -52,6 +52,9 @@ public:
     explicit QModbusRtuSerialMaster(QObject *parent = Q_NULLPTR);
     ~QModbusRtuSerialMaster();
 
+    int interFrameDelay() const;
+    void setInterFrameDelay(int microseconds);
+
 protected:
     QModbusRtuSerialMaster(QModbusRtuSerialMasterPrivate &dd, QObject *parent = Q_NULLPTR);
 
diff --git a/src/serialbus/qmodbusrtuserialmaster_p.h b/src/serialbus/qmodbusrtuserialmaster_p.h
index c3b1b5a..43fe630 100644
--- a/src/serialbus/qmodbusrtuserialmaster_p.h
+++ b/src/serialbus/qmodbusrtuserialmaster_p.h
@@ -157,7 +157,7 @@ public:
 
             m_state = Schedule; // reschedule, even if empty
             m_serialPort->clear(QSerialPort::AllDirections);
-            QTimer::singleShot(m_timeoutThreeDotFiveMs, [this]() { processQueue(); });
+            QTimer::singleShot(m_interFrameDelayMilliseconds, [this]() { processQueue(); });
         });
 
         using TypeId = void (QSerialPort::*)(QSerialPort::SerialPortError);
@@ -223,6 +223,28 @@ public:
         });
     }
 
+    /*!
+        According to the Modbus specification, in RTU mode message frames
+        are separated by a silent interval of at least 3.5 character times.
+        Calculate the timeout if we are less than 19200 baud, use a fixed
+        timeout for everything equal or greater than 19200 baud.
+        If the user set the timeout to be longer than the calculated one,
+        we'll keep the user defined.
+    */
+    void calculateInterFrameDelay() {
+        // The spec recommends a timeout value of 1.750 msec. Without such
+        // precise single-shot timers use a approximated value of 1.750 msec.
+        int delayMilliSeconds = 2;
+        if (m_baudRate < 19200) {
+            // Example: 9600 baud, 11 bit per packet -> 872 char/sec
+            // so: 1000 ms / 872 char = 1.147 ms/char * 3.5 character
+            // Always round up because the spec requests at least 3.5 char.
+            delayMilliSeconds = qCeil(3500. / (qreal(m_baudRate) / 11.));
+        }
+        if (m_interFrameDelayMilliseconds < delayMilliSeconds)
+            m_interFrameDelayMilliseconds = delayMilliSeconds;
+    }
+
     void setupEnvironment() {
         if (m_serialPort) {
             m_serialPort->clear();
@@ -233,20 +255,7 @@ public:
             m_serialPort->setStopBits(m_stopBits);
         }
 
-        // According to the Modbus specification, in RTU mode message frames
-        // are separated by a silent interval of at least 3.5 character times.
-        // Calculate the timeout if we are less than 19200 baud, use a fixed
-        // timeout for everything equal or greater than 19200 baud.
-        if (m_baudRate < 19200) {
-            // Example: 9600 baud, 11 bit per packet -> 872 char/sec
-            // so: 1000 ms / 872 char = 1.147 ms/char * 3.5 character
-            // Always round up because the spec requests at least 3.5 char.
-            m_timeoutThreeDotFiveMs = qCeil(3500. / (qreal(m_baudRate) / 11.));
-        } else {
-            // The spec recommends a timeout value of 1.750 msec. Without such
-            // precise single-shot timers use a approximated value of 1.750 msec.
-            m_timeoutThreeDotFiveMs = 2;
-        }
+        calculateInterFrameDelay();
 
         responseBuffer.clear();
         m_state = QModbusRtuSerialMasterPrivate::Idle;
@@ -255,7 +264,7 @@ public:
     void scheduleNextRequest() {
         m_state = Schedule;
         m_serialPort->clear(QSerialPort::AllDirections);
-        QTimer::singleShot(m_timeoutThreeDotFiveMs, [this]() { processQueue(); });
+        QTimer::singleShot(m_interFrameDelayMilliseconds, [this]() { processQueue(); });
     }
 
     QModbusReply *enqueueRequest(const QModbusRequest &request, int serverAddress,
@@ -323,7 +332,7 @@ public:
                     scheduleNextRequest();
                 } else {
                     m_serialPort->clear(QSerialPort::AllDirections);
-                    QTimer::singleShot(m_timeoutThreeDotFiveMs, [writeAdu]() { writeAdu(); });
+                    QTimer::singleShot(m_interFrameDelayMilliseconds, [writeAdu]() { writeAdu(); });
                 }
             } else {
                 qCDebug(QT_MODBUS) << "(RTU client) Send successful:" << m_current.requestPdu;
@@ -346,7 +355,7 @@ public:
             } else {
                 m_state = Send;
                 m_serialPort->clear(QSerialPort::AllDirections);
-                QTimer::singleShot(m_timeoutThreeDotFiveMs, [this, writeAdu]() { writeAdu(); });
+                QTimer::singleShot(m_interFrameDelayMilliseconds, [this, writeAdu]() { writeAdu(); });
             }
             break;
 
@@ -384,7 +393,7 @@ public:
     QQueue<QueueElement> m_queue;
     QSerialPort *m_serialPort = Q_NULLPTR;
 
-    int m_timeoutThreeDotFiveMs = 2; // A approximated value of 1.750 msec.
+    int m_interFrameDelayMilliseconds = 2; // A approximated value of 1.750 msec.
 };
 
 QT_END_NAMESPACE
diff --git a/tests/auto/auto.pro b/tests/auto/auto.pro
index 838eb53..2542d65 100644
--- a/tests/auto/auto.pro
+++ b/tests/auto/auto.pro
@@ -11,7 +11,8 @@ SUBDIRS += cmake \
            qmodbusserver \
            qmodbuscommevent \
            qmodbusadu \
-           qmodbusdeviceidentification
+           qmodbusdeviceidentification \
+           qmodbusrtuserialmaster
 
 qcanbus.depends += plugins
 qcanbusdevice.depends += plugins
diff --git a/tests/auto/qmodbusrtuserialmaster/qmodbusrtuserialmaster.pro b/tests/auto/qmodbusrtuserialmaster/qmodbusrtuserialmaster.pro
new file mode 100644
index 0000000..3125a27
--- /dev/null
+++ b/tests/auto/qmodbusrtuserialmaster/qmodbusrtuserialmaster.pro
@@ -0,0 +1,8 @@
+CONFIG -= app_bundle
+CONFIG += testcase c++11
+
+QT = core testlib serialbus
+
+TARGET = tst_qmodbusrtuserialmaster
+SOURCES += tst_qmodbusrtuserialmaster.cpp
+
diff --git a/tests/auto/qmodbusrtuserialmaster/tst_qmodbusrtuserialmaster.cpp b/tests/auto/qmodbusrtuserialmaster/tst_qmodbusrtuserialmaster.cpp
new file mode 100644
index 0000000..589ec46
--- /dev/null
+++ b/tests/auto/qmodbusrtuserialmaster/tst_qmodbusrtuserialmaster.cpp
@@ -0,0 +1,62 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtSerialBus module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtSerialBus/qmodbusrtuserialmaster.h>
+#include <QtSerialPort/qserialport.h>
+
+#include <QtTest/QtTest>
+
+class tst_QModbusRtuSerialMaster : public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void testInterFrameDelay()
+    {
+        QModbusRtuSerialMaster qmrsm;
+        QCOMPARE(qmrsm.interFrameDelay(), 2000);
+        qmrsm.setInterFrameDelay(1000);
+        QCOMPARE(qmrsm.interFrameDelay(), 2000);
+        qmrsm.setInterFrameDelay(3000);
+        QCOMPARE(qmrsm.interFrameDelay(), 3000);
+        qmrsm.setInterFrameDelay(-1);
+        QCOMPARE(qmrsm.interFrameDelay(), 2000);
+    }
+};
+
+QTEST_MAIN(tst_QModbusRtuSerialMaster)
+
+#include "tst_qmodbusrtuserialmaster.moc"