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M-Duino with MAX485 Module


Introduction


In this post will be shown how to connect our M-Duino PLC with the MAX485 module. 


Requeriments


 M-Duino family

MAX485 module


MAX485 Module


On-board MAX485 chip is a low-power and slew-rate-limited transceiver used for RS485 communication. Adopting half-duplex communication to implement the function of converting TTL level info into RS485 level, it can achieve a maximum transmission rate of 2.5 Mbps. 

Pinout:

Resultado de imagen de max485 pinout

Dependig on RE and DE connection the module works as receiver or transmitter. Connected to VCC transmits data and connected to GND receives data. 

It is a cheap module. You can find lots of 5 unit for less than one euro. 


Connections


In this case, for send and receive data we use Serial1 (RX1 and TX1), but it's possible to use other Serial. However, Serial2 is used by for RS-232 and Serial3 for RS-485, so it's nonsense use Serial3. That means we we have three options: Serial0, Serial1 or Serial2 (losing RS-232 communication). To enable the transmision or reception tipically use Pin 2 and Pin3.    

Here you have the connections diagram. Obviously, using one MAX485 module, it's not possible to send and receive at the send time. For that you have to connect two MAX485 modules, one to transmit and one to receive. 

Send or Receive Connections


Send and Receive Connections