Minimal documentation on how to build Modbus demo.

Author: aentinger

examples/opcua_server/README.md

@@ -0,0 +1,7 @@
+:floppy_disk: `opcua_server.ino`
+================================
+
+### How-to-build Modbus MD02 demo
+```bash
+arduino-cli compile --fqbn arduino:mbed_opta:opta examples/opcua_server -v --build-property compiler.cpp.extra_flags="-DUSE_MODBUS_SENSOR_MD02=1"
+```

examples/opcua_server/opcua_server.ino

@@ -13,10 +13,6 @@
 #include "mbed_mem_trace.h"
 #endif
 
-#ifndef USE_MODBUS_SENSOR_MD02
-# define USE_MODBUS_SENSOR_MD02 (1)
-#endif
-
 #if USE_MODBUS_SENSOR_MD02
 # include <ArduinoRS485.h>
 # include <ArduinoModbus.h>