This post describes how to gain direct access to Arduino board pins inside the Ardbox and MDuino PLCs. This allows to work with the PLCs in the same way as using an Arduino, in other words, pins at 5V and configurable as input or outpts.
Also, this enables usage of sensors working at lower voltages than industrial standards 10V dc/24Vdc. NOTE:Make sure the voltage DOES NOT EXCEED 5VDC!!!!!!!!
Following are listed the connections with direct access to the Arduino board pins.
Ardbox: DE-D7 // RE-D4 // SDA-PIN2 // SCL-PIN3
MDuino: SCL // SDA // RX0 // TX0 // RX1 // TX1 // Pin3 // Pin2
In order to enable the direct connection to Arduino pins, the configuration switches for these connections must be set to OFF position.