Get Started With UM402 LoRa (433MHz UART) Using Arduino UNO




Introduction: Get Started With UM402 LoRa (433MHz UART) Using Arduino UNO

This project is done by a group of students from Singapore Polytechnic, School of Electrical and Electronic Engineering. We have a total of 3 members in our group, Woon Jun Shen, Li Desheng, Eugene Loh Yong Jing. Our supervisor is Mr Teo Shin Jen.

The purpose of our project is to create a smart, solar-powered and portable device for post disaster relief. It is designed for the victims of natural disaster so that the rescue team will be able to locate where the victim is.

In this project, we are trying to make point-to-point connection with UM402 LoRa which we got it from AliExpress as this is our first goal.

Step 1: Connect UM402 With Arduino UNO

In order to build the things up, the components required are:

1. 2x Arduino UNO
2. 2x UM402 Manthink 433MHz UART (SX1278/SX1276)
3. Jumper wires


1. GND => GND
2. VCC => 3.3V
3. SETA => Any GPIO set to 0 / GND
4. RXD => Pin 3
5. TXD => Pin 2
6. AUX => NC
7. SETB => Any GPIO set to 0 / GND

Set A and Set B pins are connected to GND at Arduino UNO board. According to the UM402 Introduction Guide (link in the reference), UM402 has 4 working modes which is normal, awaken, low power (sleep and power saving) and set. The four working modes are determined by the level of Set A and Set B.

As we are using Send and Receive which is the Normal Mode, we connect SETA and SETB to GND pins at the Arduino UNO board.

Step 2: Programming the UM402 With Arduino IDE

For Transmit and Receive, we need two Arduino IDE to run at the same time. So, we install one Arduino IDE in C Drive and another one in D Drive. Run both at the same time and copy the code to both the Arduino IDE. The code of the program is uploaded to GitHub, Code for UM402.

When you are trying to compile, remember to change the Board Setting to Arduino UNO at 'Tools' tab as shown in the diagram. Once it is done with uploading, open up the Serial Monitor at each side.

Now, you can try to type some words at the Serial Monitor and wait for it to appear at another side. For example in my video, when I type Hello! in Serial Monitor COM9, it will be sent over and appear at Serial Monitor COM8.

Step 3: Simple Demo



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6 Discussions

Hello, is that any Arduino library of LoRa module need to be added to the program?


1 year ago

Hi, If you want to set the address for each transmitter/receiver module, how do you do that?


Would um402 get damaged if we provide 5v to its vcc.

How much range did you get when you did this project.

Please do reply soon and Thanks for sharing this project.

1 reply