Connecting RS232 Device to Arduino Mega via Hardware Serial (TX2/RX2)

Projects Networking, Protocols, and Devices
1

Hello everyone,

I am working on a project where I need to interface an RS232 device with an Arduino Mega. The device uses RS232 for communication, and I want to connect it to the Hardware Serial pins (TX2/RX2) of the Arduino Mega.

Setup:

  • RS232 device has an RS232 interface (female DB9 connector).
  • The Arduino Mega has multiple hardware serial ports (e.g., TX2, RX2).
  • I have a MAX232 module that converts the TTL signals from the Arduino to RS232 levels.

Communication Commands:

We will be sending commands from the Arduino to the RS232 device.

For example, if the RS232 device expects a certain command to retrieve data or control some functionality, the Arduino Mega will send it using the TX2 pin to the RS232 device. Once the device processes the command, it will send a response, which will be received on the RX2 pin of the Arduino.

My Questions:

  1. How should I connect the MAX232 module to the Arduino Mega’s Hardware Serial pins (TX2, RX2)?
  2. What pinouts do I need to use for the RS232 side of the MAX232 and the Arduino’s TX2/RX2?
  3. Do I need any additional configuration or setup to communicate with the RS232 device properly using the Arduino Mega’s TX2/RX2?
  4. Is there any specific code or library needed for RS232 communication?
2

This is for TX1/RX1, you can adapt it to TX2/RX2.

Instead of Serial1, you would use Serial2.

3

Bad example since it never worked.

4

The post literally says "tested with"... so yes it worked.

5

Some good advise.
Don't use any forum topic as an example of how to do things if it has never been marked solved.

6

Nice moving of goal posts there.

7
  1. Please provide a link the the module you are using
  2. Once we see which module your are using we can answer this question.
  3. No
  4. No
9
10

Use Serial1 on the Mega

Connect like this:

RX -> Pin 18
TX -> Pin 19
GND -> GND
VCC -> 5V

You will need a cross-over cable (null-modem) to connect the two DB9 connectors together

11

okay

12

But i think we need to connect
pin18(TX1) ---> TX
pin19(RX1) ----> RX
5V ----> Vcc
GND ---->GND

13

From the website

14

image
image927×610 106 KB

but this will give the connection like this and the dummy code is worked

15

Yes it would, so I was wrong in showing you that picture
You need to connect as I specified in post #10
I'll repeat it here

RX -> Pin 18
TX -> Pin 19
GND -> GND
VCC -> 5V

Then you use Serial1 in your code.

16

pin18 means it is tx1 and from the image i given, we should connect tx1(pin18) with tx Pin of MAX3232 and rx1 (pin19)with rx pin of MAX3232

17

That image does not appear on the website where you bought the RS232 converter. Maybe it is correct for the module they are using in the image but it doesn't look like the module you have.

18
1 Like
19

Then you bought the wrong module.
If you follow that tutorial then you need to buy the exact same components they used in the tutorial. There are many different versions of the RS232 converter that you can buy and they are not all the same.

20

The module used in the example is MAX232 .and the module I have is MAX3232.
The MAX3232 is compatible with the MAX232 for RS232 communication, with the key difference being its ability to operate at a wider voltage range (3.0V to 5.5V). This makes it suitable for low-power systems.

  • MAX232: Works with a 5V power supply.
  • MAX3232: Works with a wider range of power supply voltages, typically 3.0V to 5.5V.

So i think we can directly substitute the MAX3232 for the MAX232 without issues, as long as the supply voltage and capacitor values are suitable for the MAX3232

21

They are completely different ICs.
You CANNOT DIRECTLY subsitute one for the other.