Create a copy of RTU Layer as a starting poiont for building the ASCII Layer

Author: Karl Herbig

include/modbuspp.h

@@ -17,6 +17,7 @@
 #pragma once
 
 #include <modbuspp/rtulayer.h>
+#include <modbuspp/asciilayer.h>
 #include <modbuspp/tcplayer.h>
 #include <modbuspp/master.h>
 #include <modbuspp/server.h>

include/modbuspp/asciilayer.h

@@ -0,0 +1,206 @@
+/* Copyright © 2018-2019 Pascal JEAN, All rights reserved.
+ * This file is part of the libmodbuspp Library.
+ *
+ * The libmodbuspp Library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * The libmodbuspp Library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the libmodbuspp Library; if not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include <modbuspp/netlayer.h>
+
+namespace Modbus {
+
+  /**
+   * @class AsciiLayer
+   * @brief RTU serial link layer
+   *
+   * This class can not and should not be instantiated by the user.
+   * It provides access to properties and methods specific to the RTU layer.
+   *
+   * An instance of this class is created by the constructor @b Device::Device()
+   * of the @b Device class (or its derived classes) if the RTU layer is selected.
+   *
+   * Access to this instance is done using the Device::rtu() method.
+   *
+   * @sa Device::Device()
+   * @sa Device::rtu()
+   * 
+   * @author Pascal JEAN, aka epsilonrt
+   * @copyright GNU Lesser General Public License
+   */
+  class AsciiLayer : public NetLayer {
+    public:
+
+      /**
+       * @brief Constructor
+       */
+      AsciiLayer (const std::string & port, const std::string & settings);
+
+      /**
+       * @brief Name of the serial port
+       *
+       * This property specifies the name of the serial port handled by the
+       *  OS, eg. "/dev/ttyS0" or "/dev/ttyUSB0".
+       */
+      const std::string & port() const;
+
+      /**
+       * @brief Return the baudrate
+       */
+      int baud() const;
+
+      /**
+       * @brief Return the parity
+       */
+      char parity() const;
+
+      /**
+       * @brief Return the bits of stop
+       */
+      int stop() const;
+
+      /**
+       * @brief Get the current serial mode
+       *
+       * This function shall return the serial mode currently used.
+       *
+       * - @b Rs232: the serial line is set for RS232 communication. RS-232
+       *  (Recommended Standard 232) is the traditional name for a series of
+       *  standards  for serial binary single-ended data and control signals
+       *  connecting between a DTE (Data Terminal Equipment) and a DCE
+       *  (Data Circuit-terminating  Equipment).
+       *  It is commonly used in computer serial ports
+       * - @b Rs485: the serial line is set for RS485 communication. EIA-485,
+       *  also known as TIA/EIA-485 or RS-485, is a standard defining the electrical
+       *  characteristics of drivers and receivers for use in balanced digital
+       *  multipoint systems. This standard is widely used for communications in
+       *  industrial  automation because it can be used effectively over long
+       *  distances and in  electrically noisy environments.
+       * .
+       * This function is only available on Linux kernels 2.6.28 onwards.
+       *
+       * @return return the current mode if successful.
+       * Otherwise it shall return @b UnknownMode (-1) and set errno.
+       * @sa setSerialMode()
+       */
+      SerialMode serialMode();
+
+      /**
+       * @brief Set the serial mode
+       *
+       * This function shall set the selected serial mode @b mode.
+       *
+       * @return true if successful.
+       * Otherwise it shall return false and set errno.
+       * @sa serialMode()
+       */
+      bool setSerialMode (SerialMode mode);
+
+      /**
+       * @brief Get the current RTS mode
+       *
+       * This function shall get the current Request To Send mode
+       *
+       * @return the current RTS mode if successful.
+       * Otherwise it shall return @b UnknownRts (-1) and set errno.
+       * @sa setRts()
+       */
+      SerialRts rts();
+
+      /**
+       * @brief Set the RTS mode
+       *
+       * This function shall set the Request To Send mode to communicate on a
+       * RS485 serial bus.
+       *
+       * @return true if successful.
+       * Otherwise it shall return false and set errno.
+       * @sa rts()
+       */
+      bool setRts (SerialRts rts);
+
+      /**
+       * @brief Get the current RTS delay
+       *
+       * This function shall get the current Request To Send delay period.
+       * @return the current RTS delay in microseconds if successful.
+       * Otherwise it shall return -1 and set errno.
+       * @sa setRtsDelay()
+       */
+      int rtsDelay();
+
+      /**
+       * @brief Set the RTS delay
+       *
+       * This function shall set the Request To Send delay period in microseconds.
+       *
+       * @return true if successful.
+       * Otherwise it shall return false and set errno.
+       * @sa rtsDelay()
+       */
+      bool setRtsDelay (int us);
+
+      /**
+       * @overload
+       *
+       * @warning This function is not supported by Windows !
+       */
+      virtual int sendRawMessage (const Message * msg);
+      
+      /**
+       * @overload
+       */
+      virtual bool prepareToSend (Message & msg);
+
+      /**
+       * @overload
+       */
+      static bool checkMessage (const Message & msg);
+
+      /**
+       * @brief Extracts the baudrate from a settings string.
+       * @return the baudrate found. if no value is found, returns the default
+       * value, ie 19200.
+       */
+      static int baud (const std::string & settings);
+
+      /**
+       * @brief Extracts the parity from a settings string.
+       * @return the parity found. if no value is found, returns the default
+       * value, ie E for Even parity.
+       */
+      static char parity (const std::string & settings);
+
+      /**
+       * @brief Return the stop bits from a settings string.
+       *
+       * @return the number returned is determined based on the parity found.
+       * If the parity is None, this function returns 2, otherwise returns 1.
+       */
+      static int stop (const std::string & settings);
+      
+      /**
+       * @brief Performing Modbus CRC16 generation of the buffer @b buf
+       */
+      static uint16_t crc16 (const uint8_t * buf, uint16_t count);
+
+    protected:
+      class Private;
+      AsciiLayer (Private &dd);
+
+    private:
+      PIMP_DECLARE_PRIVATE (AsciiLayer)
+  };
+}
+
+/* ========================================================================== */

include/modbuspp/global.h

@@ -48,6 +48,14 @@ namespace Modbus {
      * protocol communication.
      */
     Rtu,
+    /**
+     * @brief ASCII backend
+     *
+     * The ASCII backend is used in serial communication.
+     * The hex value of the binary data is transmitted 
+     * in ASCII character representation.
+     */
+    Ascii,
     /**
      * @brief TCP backend
      *