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I'm doing an Arduino Uno project and I need to control some motors using my mobile phone through bluetooth. I contacted an Arduino reseller in my country and he said that he has bluetooth shield for $16 and bluetooth module for $40, I don't know which one to buy.

To make things even more confusing, this guy has done something similar to what I wanted to do using this which is only around $6.

But I've also seen other projects that are done using the shield, so what to buy? I don't really care about the price, I am willing to pay, but I don't know which one to buy.

At first I thought that Arduino bluetooth shield is a shield (cover) that protects the module but this guy was able to connect Arduino using the shield only.

My questions are: what is the difference between the shield and the module? What are the differences between different Arduino bluetooth modules? What do you usually buy to connect an android device to Arduino using bluetooth?

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They will all probably work, some easier than others.

First, a shield is not a cover and is defined at arduino.cc as: "Shields are boards that can be plugged on top of the Arduino PCB extending its capabilities".

This means that shield provides functionalities like, e.g. bluetooth.

The bluetooth modules are similar, but requires different levels of work and programming knowledge. The shields are made to make it easier for people new to programming do some cool projects. I would suggest you follow a tutorial and maybe buy exactly the same module if you feel that you knowledge of C/C++ is at a beginner level.

I myself have several of the $6 module and it is also easy to get started with. You need to connect 4 cables (power, ground, transmit (tx) and receive (rx) and send data via correct UART/Serial line at the default baudrate (9600).

Android will be the device initiating the connection so when you search for available bluetooth devices the shield/module will show up in the list. Once paired you can send/receive data.

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    \$\begingroup\$ So the difference is the programming language? i am an intermediate C++ guy, since i am a computer science student \$\endgroup\$ – Lynob Nov 21 '13 at 23:58
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    \$\begingroup\$ @Fischer: Arduino libraries are usually C++ based and from what I have seen is very easy to interface with serial communication like UART. Me myself used C and no library which means one have to set appropriate registers and write a initialize, send and receive function as a minimum for two way communication. The hardware does not really limit you to any programming languages, but C++ dominate with arduino which means it will be easier to find examples, tutorials and get help from the community. \$\endgroup\$ – iQt Nov 22 '13 at 0:10
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The problem is that you do not link to the ones your reseller sells. The term shield and module are thrown around a lot, and in the case of some of the higher tech boards, arn't fairly uniform.

In this specific case, you really need to be sure before you waste your money. Look below for many of the combinations you can find. Since you arn't in the US, I'm assuming that the reseller has the module, the actual bluetooth chip and parts, and a shield, a pcb where the module plugs into (or has to be soldered on). Double check!

Bluetooth "Board" or "Module" enter image description here

Bluetooth "Board" or "Module" enter image description here

Bluetooth "Board" or "Module" (Unsoldered) enter image description here

Bluetooth "Board" or "Module" enter image description here

Bluetooth Shield for Arduino (Xbee shield with "Xbee" Bluetooth module/shield. You only get the top small board, you would need the xbee shield) enter image description here

Bluetooth Shield for Arduino enter image description here

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