I got the majority of the parts for my build from LCSC.

You will need:

1) Ra-02 LoRa module

2) ESP8266

3) OLED display

4) Passive components like resistors and capacitors

You would require the PCB to solder these components which we will take a look at the next step.

You must check out JLCPCB for ordering PCBs online for cheap!

You get 10 good quality PCBs manufactured and shipped to your doorstep for 2$ and some shipping. You will also get a discount on shipping on your first order. To design your own PCB head over to easyEDA, once that is done upload your Gerber files onto JLCPCB to get them manufactured with good quality and quick turnaround time.

Mainly there are 4 aspects in connections here:

1) ESP8266 just to function correctly needs some pull up and pull down the connection for G0, G15, EN and RST.

2) Ra-02 and the ESP8266 modules are connected to each other using the SPI protocol

3) OLED and the ESP8266 connect to each other using the I2C bus

4) All the modules need to be connected to power rails for them to operate.(Obvious :P)

Solder all the components to the PCB.

I would suggest to solder the low height components on the PCB first and then move to components with more height like the headers etc.

Before powering the module test all the connections using a multimeter for bad solder joints and short circuits.

1) Download the code from here.

2) Open the code in the Arduino IDE.

3) Connect the PCB to the computer using the CP2102 USB to serial converter or any other similar device.

4) Reset the ESP8266 module while pulling the GPIO0 low (keep the G0 button pressed while reset).

5) Now hit the upload button on the IDE. Upload might fail once or a couple of times so you must try 2-3 times in case of failure.

6) Disconnect the USB to serial adapter and connect the OLED display if you haven't yet.

7) Program the other part of the project Reciever/Transmitter

Once you've coded both the modules you can attach them to power.

In my case I attached my transmitter to a power bank, the receiver to a laptop for access to a serial monitor.

As soon as I powered the transmitter I started to see messages on the serial monitor connected to the receiver.

Mine works like a charm!