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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.
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:
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); } }