How to connnect Arduino to Wemos D1 (send data)? I made a project with an Arduino Uno, a 16x2 LCD display and a DS18B20 temperature sensor. It shows the temperature in the display:



I want to connect it to Internet so I got a Wemos D1 Mini. It works great: it send data through my router.

But I need to connect my project with the Wemos D1 Mini:

I think that I just need to send the data (temperatures grades) from my project to Wemos so then Wemos resolve it.

How can I do it?
A) Throw out the Arduino, and just connect your display and sensor to the WeMos directly.   
B) Connect the Arduino to the WeMos using UART, SPI or I²C and send the temperature value to the WeMos. Keep in mind that the Arduino UNO is a 5V device, and the maximum voltage for the ESP8266 is 3.3V, so you'll need a level shifter.
You can send the temperature as a binary value (beware of framing errors), but the easiest way is to use a text-based protocol. Since you just have to send a single value, you can just use a single delimiter (e.g. new line). That makes it very easy to parse.