Add sketch example of using SoftwareSerial on NANO RS485 industrial board

Author: kuanting

library/MultiModbus/library.properties

@@ -6,6 +6,6 @@ sentence=Support multi-Modbus RTU communication via RS485 (RS485-to-UART ICs req
 paragraph=MultiMobus supports multiple Modbus RTU servers and clients over RS485 on one board. RS485-to-UART ICs are required.
 category=Communication
 url=
-architectures=megaavr,samd,mbed_nano,mbed_portenta,mbed_opta
+architectures=*
 includes=MultiModbus.h
 depends=RS485

sketch/sketch_multi_modbus_nano_software_serial/sketch_multi_modbus_nano_software_serial.ino

@@ -0,0 +1,56 @@
+// Author: Kuan-Ting Lai
+#include <RS485.h>    // https://github.com/RobTillaart/RS485
+#include <MultiModbus.h>
+#include <SoftwareSerial.h>
+
+// This sketch uses Arduino NANO 485 industrial control board as an example. 
+// You can find the board's information below:
+// https://www.aliexpress.com/item/1005003710057347.html
+// Pinout diagram:
+//https://ae01.alicdn.com/kf/Sdf186ca8d45649cd8bef91bf5d6d2f16T.jpg
+// 
+// 中文相關訊息
+// https://www.ruten.com.tw/item/show?22023652957564
+// https://ruten-proteus.blogspot.com/2020/06/1try-vtscada-arduino-nano-485-modbus-rtu.html
+
+#define RS485_BAUD_RATE 19200
+#define MODBUS_DEVICE_ID 1
+
+const uint8_t sendPin  = -1;  // Our board has auto-direction
+
+SoftwareSerial sw_serial(13, 12); // D13/D12 for RX/TX
+RS485 rs485(&sw_serial, sendPin);
+
+ModbusRTUServer modbus_server(rs485);
+
+
+void setup() {
+  Serial.begin(19200);  // Debug
+  //while (!Serial);    // Avoid endless loop when running without USB COM port
+  
+  sw_serial.begin(RS485_BAUD_RATE);
+  
+  if (!modbus_server.begin(MODBUS_DEVICE_ID, RS485_BAUD_RATE)) {
+    Serial.println("Failed to start Modbus RTU Server !");
+    while (1);
+  }
+
+  // configure a single coil at address 0x00, Modbus client will start to read/write from 0x01
+  modbus_server.configureCoils(0x00, 1);
+  
+  Serial.print("MultiModbus is ready! Device ID is ");
+  Serial.println(MODBUS_DEVICE_ID);
+  
+}
+
+
+void loop() {
+  int packetReceived;
+
+  // poll for Modbus RTU requests
+  packetReceived = modbus_server.poll();
+  if(packetReceived) {
+    int coilValue = modbus_server.coilRead(0x00);
+    Serial.println(coilValue);
+  }
+}