fix: Fixes #5

This issue was due to a bad management of the dynamic memory.
The implementation of the Modbus class has been revised to correct this problem, but also that of writeMultipleCoils() which was not working correctly.
The Reading methods have been reviewed and optimized.

Author: epsilonrt

issues/modbus-arduino-Issue5/.gitignore

@@ -0,0 +1,5 @@
+.pio
+.vscode/.browse.c_cpp.db*
+.vscode/c_cpp_properties.json
+.vscode/launch.json
+.vscode/ipch

issues/modbus-arduino-Issue5/platformio.ini

@@ -0,0 +1,71 @@
+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter
+;   Upload options: custom upload port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;   Advanced options: extra scripting
+;
+; Please visit documentation for the other options and examples
+; https://docs.platformio.org/page/projectconf.html
+
+[platformio]
+default_envs = mkrvidor4000
+
+[env:teensy41]
+platform = teensy
+board = teensy41
+framework = arduino
+lib_extra_dirs = ../../..
+;lib_deps = epsilonrt/Modbus-Serial@^2.0.3
+
+[env:mkrvidor4000]
+platform = atmelsam
+board = mkrvidor4000
+framework = arduino
+lib_extra_dirs = ../../..
+;lib_deps = epsilonrt/Modbus-Serial@^2.0.3
+
+[env:mkrvidor4000-debug]
+platform = atmelsam
+framework = arduino
+board = mkrvidor4000
+debug_tool = atmel-ice
+
+
+; Debugger (gdb) support 
+; https://docs.arduino.cc/tutorials/mkr-wifi-1010/mkr-jlink-setup
+; https://gojimmypi.blogspot.com/2018/12/swd-debugging-arduino-mkr-wifi-1010.html
+
+build_type = debug
+lib_extra_dirs = ../../..
+;lib_deps = epsilonrt/Modbus-Serial@^2.0.3
+
+; activate Dual USB just as README says
+build_flags =
+    -DDEBUG                   # Comment out to disable debugging.
+;debug_build_flags = -O0 -g2 -ggdb2
+debug_build_flags = -O0 -ggdb3 -g3
+
+[env:esp32]
+framework = arduino
+platform = espressif32
+; change for your board : https://registry.platformio.org/platforms/platformio/espressif32/boards
+board = esp32doit-devkit-v1
+;board_build.f_cpu = 240000000L
+lib_extra_dirs = ../../..
+;lib_deps = epsilonrt/Modbus-Serial@^2.0.3
+;upload_port = COM9
+
+[env:esp32-debug]
+; https://dzone.com/articles/eclipse-jtag-debugging-the-esp32-with-a-segger-j-l
+; https://docs.platformio.org/en/latest/tutorials/espressif32/arduino_debugging_unit_testing.html
+; https://community.platformio.org/t/esp32-and-segger-jlink-tip-for-interface-setup-configuration/25964
+framework = arduino
+platform = espressif32
+; change for your board : https://registry.platformio.org/platforms/platformio/espressif32/boards
+board = esp32doit-devkit-v1
+;board_build.f_cpu = 240000000L
+lib_extra_dirs = ../../..
+;lib_deps = epsilonrt/Modbus-Serial@^2.0.3
+upload_port = COM1
+debug_tool = jlink

issues/modbus-arduino-Issue5/src/main.cpp

@@ -0,0 +1,41 @@
+#include <ModbusSerial.h>
+
+// Used Pins
+const byte LedPin = LED_BUILTIN;
+const byte TxenPin = -1;    // -1 disables the feature, change that if you are using an RS485 driver, this pin would be connected to the DE and /RE pins of the driver.
+
+#define MySerial Serial1  // define serial port used, Serial most of the time, or Serial1, Serial2 ... if available
+const unsigned long Baudrate = 38400;
+
+const byte SlaveId = 10;
+
+const byte FirstReg = 0;
+const byte Lamp1Coil = FirstReg;
+const byte NofRegs = 32;
+
+ModbusSerial mb(MySerial, SlaveId, TxenPin);
+
+void setup() {
+
+  // MySerial.begin(Baudrate);  // works on all boards but the configuration is 8N1 which is incompatible with the MODBUS standard
+  // prefer the line below instead if possible
+  MySerial.begin (Baudrate, MB_PARITY_EVEN);
+
+  mb.config(Baudrate);
+
+  for (byte i = 0; i < NofRegs; i++) {
+
+    mb.addHreg(FirstReg + i, i);
+    mb.addIreg(FirstReg + i, i);
+    mb.addCoil(FirstReg + i, i % 2);
+    mb.addIsts(FirstReg + i, (i + 1) % 2);
+  }
+
+  pinMode(LedPin, OUTPUT);
+}
+
+void loop() {
+
+  mb.task();
+  digitalWrite(LedPin, !mb.Coil(Lamp1Coil));
+}

library.json

@@ -1,6 +1,6 @@
 {
   "name": "Modbus-Arduino",
-  "version": "1.1.2",
+  "version": "1.2.0",
   "keywords": "modbus, server, slave, rtu, tcp",
   "description": "A library that allows your Arduino to communicate via Modbus protocol, acting as a slave. Application layer library (OSI 7), used by all implementations over serial line and TCP/IP.",
   "homepage": "https://epsilonrt.github.io/modbus-arduino",

library.properties

@@ -1,5 +1,5 @@
 name=Modbus-Arduino
-version=1.1.2
+version=1.2.0
 author=Pascal Jean aka epsilonrt,André Sarmento Barbosa
 maintainer=epsilonrt
 sentence=A library that allows your Arduino to communicate via Modbus protocol, acting as a slave.