Using 3 UART together

Projects General Guidance
1

I am making a project where I want to control my home appliances with mobile. for that I have connected Android mobile to Arduino through USB. Now, I want to transfer data to another arduino(more than 1) placed at a distance for that I`m gonna use RF transreceiver module.

As this project need 2 or more UART I need Arduino Mega which can communicate through USb to android and send data through RF to another Arduino Mega.

I like to have a second opinion before I make the purchase, so guys please tell is this sounds feasible??
as there are many types of Mega and RF transreceiver available, if you can point out some for my need, would be great help.

Thank You

2

There is the Software Serial library that lets you use 2 I/O pins as serial, it is standard in your IDE.

3

Yes, I will try that, but I think using a hardware serial would be suitable as I need to use it for a long time.

4

So? Software serial works for a long time. It doesn't wear out.

For home appliance control you don't need so much as you might imagine. I have code monitoring a greenhouse with multiple temperature sensors plus humidity and CO2 sensor plus relays to run air and water control plus SD and GSM module. Sensors read every minute and control relays as often except when the GSM blocks code, the everything waits over 30 seconds for GSM to connect after which everything runs and GSM sends data to a web site. The whole operation exceeds needs, the owner is very happy with it.

That code mostly does nothing. It has room to monitor dozens of times as much as it does. I want to put the GSM on a dedicated controller and not have the wait, but there is no need for it now.

If you are checking and messaging 100x per second, maybe then you begin to require an extra serial port.

Buuuuuuut! If you want to do for fun then that is another thing! Make a breadboard 1284P Duino!
For a chip in the $10 or less price range (if you shop, if your country doesn't tax imports massively) you get 40 pins that can plug in socket or breadboard, 2 serial ports, 16K RAM, 128K flash, SPI, I2C, etc.

Here is how with all needed software linked to:
The 1284P is the second example, halfway down.

BTW, wireless is cool but you can also wire Duinos together. Close together on SPI bus they can communicate at 2 megabyte per second speed. Serial is SLOW compared.

If you want to use multiple cheap sensors, temperature/light/humidity/etc, then look into 1-wire and 2-wire bus. They are slower than serial but allow over 100 devices on the same line.

And again, what in home control needs to happen in less than 1 second?