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How to use a MAX232 with Arduino based PLC

Introduction

On this post it is showed how to connect a Max3232 to an M-Duino PLC family.                                      M-Duino PLC family

Max3232 has a two lines of RS-232 communication and their respective two channels of TTL and also power supply pins (3-5,5V-GND). 


Requirements

Ethernet or 20 I/Os PLC:      Ethernet PLC >>       

Industrial Shields boards:   Industrial Shields Boards >>


Implementation

How to connect M-Duino PLC with the Max232?

M-Duino has two available serial TTL, RX1/TX1 (or Serial1) and RX3/TX3 (or serial3). Connecting RX1/TX1 with T1IN/R1OUT and RX3/TX3 with T2IN/R2OUT the MAX3232 is ready to transmit and receive the data (don’t forget to connect the power supply). Next it is showed a electric connections diagram:

 electric connections diagram

Once the connections are set it’s possible to proceed to upload a sketch to test if the MAX232 are working as expected. On this sketch it’s just used one of them because the other it’s just a copy. Actually the MAX232 is doing all the hard work, for the user just have to code as a normal TTL serial port using serial1 or serial3 as is showed bellow.

Example

Next it is showed the test sketch:

#define TTL Serial1 // Serial1 or Serial3

/////////////////////////////////////////////////////////////////////////////
void setup() {
  Serial.begin(9600L);
  Serial.println("ttl started");

  TTL.begin(115200L);
}

/////////////////////////////////////////////////////////////////////////////
void loop() {
  if (Serial.available()) {
    byte in = Serial.read();
    TTL.write(in);
  }

  if (TTL.available()) {
    byte in = TTL.read();
    Serial.write(in);
  }
}

 

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