Ref. IS.MDUINO.58+
Rev. 0: 30-08-2019
32
M-Duino Arduino I/Os 5V pins
9
The M-Duino has some of the Mega board pins available. These pins can be programmed
according to Arduino features such as I/Os operating at 5V or any additional features present
in the pins (for example I2C communication in pins SCL and SDA). As this pins are directly
connected to the Arduino Mega board they are not as well protect as the normal inputs. These
pins are mainly meant to be used as prototyping.
The Arduino board available pins are summarized in the table below. In order to access some
of these pins the configuration switch must be set to OFF position (see section 8) and some
extra considerations must be taken in consideration when using these pins.
*IMPORTANT:
Do not connect the terminals in the chart above to voltages higher than 5V.
These terminals provide direct access to the Mega board.
A part from the switch configuration there are some special conditions depending on these 5V.
Now it is going to be shown the considerations to operate with these pins.
9.1
I2C pins – SDA/SCL
The I2C protocol is meant to work in a pull-up configuration. A pull-up configuration means
that when the pin is at rest (nothing connected to it) it always reads a HIGH value. In this case
it reads 5V when nothing is connected. The pull-up configuration is stablished by default in
these pins.
If it is meant to work them as a GPIO at 5V, it has to be considered that they are pull-up
inputs.
*IMPORTANT: I2.5 & I2.6 are not pull-up inputs although they are referred to the I2C pins
(switch configuration). There is a “reverse pull-up circuit “that is stablished in order to have the
same behaviour as the other inputs.
9.2
Serial 0 – RX0/TX0
The Serial0 protocol can work also as a 5V pin. These pins should be used ultimately, only in
case that all the 5V pins are already performing a function. This is because they are shared
with the USB interface. If using these pins, the USB communication cannot be working at the
same time. When the PLC is not installed, the USB communication is normally required for
debugging, uploading and intercommunicating with the Ethernet controller. If using both
interfaces at
the
same time the Arduino board will get blocked.
M-Duino terminal
Arduino pin
Enable Arduino pin
SCL
21
Communication switch: OFF
SDA
20
Communication switch OFF
RX0
0
TX0
1
RX1
19
Communication switch: OFF
TX1
18
Communication switch: OFF
MISO
50
MOSI
51
SCK
52
Pin 3
3
Communication switch: OFF
Pin 2
2
Communication switch: OFF
Summary of Contents for M-DUINO PLC ARDUINO ETHERNET 58
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