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

1 Person Made This Project!


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Question 3 years ago on Step 3

Hello my friend, I have done all the steps and I have not managed to make the communication, I do not know if it is a problem because my LoRa is the E32T 433T20D (SX1278), the pins are identical to the ones you use, I have MOSI, MISO, RX, TX, AUX, VCC and GND. What can I do, I have done many things like leaving MOSI MISO AUX on the ground, but still nothing, I have also made different connections and even without answers, I do not know if my LoRa does not work, I do not know how to check if it still works. Try the program RF setting 3.49 (Ebyte) and there it detects me with my USBUART but I do not know if it really works, I do not know what the problem is, I'm crazy!. thanks

Answer 2 years ago

Same module here. My module for some reason does not have any pin information. I'm a little bit lost on where to connect stuff. This tutorial module seems to be very similar. But obviously not the same as ours.
Were you able to manage to make your 433T20D work?
I just got the USB to TTL modules; and I don't mean to waste your time but; can you help me with the USB to TTL Module? (Never used that before).
I'm willing to work with you and share my work if you like in order for us both accomplish our needs.

Best regards;


4 years ago

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


Reply 3 years ago

This project only implements the PHY layer (LoRaPHY), the physical layer. MAC addresses and IP addresses are upper layer functions. To get addressing, you have to implement the LoRaWAN using additional code. There are libraries that enable this.


Question 4 years ago

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


Answer 3 years ago

This project does not require any additional Arduino library. It connects an Arduino Uno to a self-contained LoRa module. The communications only rely on the PHY layer (LoraPHY). The upper layers (LoraWAN) are not implemented.

Consider this as a point-to-point "Hello World" project. It shows that the Arduino Uno and the LoRa module are connected properly.

The next steps would be to add more functionality:
1) Have the device control something and/or take a sensor reading.
2) Add a human interface for sending and receiving messages.
3) Implement the LoRaWAN layer to enable this device to talk to a LoRaWAN gateway

If the intent of the project was to locate each other, one obvious "sensor" would have been to add a GPS module to relay the location.

What about a keyboard and display?

How would you display the location on a map like this one?

Eby Jimmy
Eby Jimmy

5 years ago


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.


5 years ago

Thanks for sharing!


Reply 5 years ago