In the previous test, performs the communication between Arduino Mega 2560 and a Modbus simulator slave THROUGH the USB port that commonly have our arduino, in this case we will test with an Arduino as Master Modbus but via RS-232 with our PC - simulator modbus slave.
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Step 1: Modbus Master Arduino Test Part 1
Step 2: MAX232
MAX232 is used, voltage converter TTL to RS232
Step 3: Final Test
Thanks to the creator of the library smarmengol.
Gracias al creador de la libreria smarmengol.