Archive for the “bluetooth” Category

For those who are looking for new development ideas to ride out these difficult times here I come with something interesting. Today I am going to talk a little bit about something that you probably haven’t heard of: Bluetooth Low Energy.

We all know what Bluetooth is I would dare to say that all of you have used it as it comes with any mobile phone with a medium-low frequency range. You already know that we can create data connections (like using the SPP profile), audio connections and much more with Bluetooth. But with regards to consumption, Bluetooth has always been limited and this also limits certain applications. Lots of people turn Bluetooth off on their mobiles if they aren’t using it as it drains the battery quickly. You can imagine that it’s not feasible Bluetooth connectivity modules with battery powered devices.

So recently a new standard has appeared called BLE (Bluetooth Low Energy). This new Bluetooth (which from my point of view only has the name and nothing else) is designed for low power applications, which is suggested by its name. To date no mobiles have this technology but in coming months we will see if new mobiles with Bluetooth Low Energy technology are going to appear.

But will a Bluetooth Low Energy device be compatible with a standard Bluetooth device?
Well, no. What happens is the telephones will be dual. They will set up a standard Bluetooth module as usual but with a Bluetooth Low Energy module. The standard Bluetooth can be turned off like in any terminal but the Bluetooth Low Energy cannot. ;)

bluetooth-low-energy

Bluetooth Low Energy is designed to efficiently transmit small quantities of information at low speeds. If we compare the consumptions of the standard Bluetooth and Bluetooth Low Energy, we see that it’s 15 times more efficient. In order to achieve this efficiency, 3 basic concepts of how it works have been optimized:

1.-Connection modes and discovery

With a standard Bluetooth module, a device that wants to receive a connection or is in visible mode should enable its receiver for long periods of time so that it’s awake and waiting to receive a packet if someone wants to communicate with it. This means there is at least 22ms of activity, so 32 different frequencies should be scanned and it should take a significant amount of time checking each one before moving onto another.

On the other hand, with Bluetooth Low Energy, when a device wants to receive a connection it only needs to send 3 small packets (on broadcast) and then it will quickly receive a connection or data if there is another device that wants to communicate with it. It only takes 1.4ms, about 17 times less than with normal Bluetooth.

Furthermore, you can include application data in these broadcast packets. This is very important because it means that with Bluetooth Low Energy we will be able to use broadcast in our applications without establishing a connection. You can imagine the amount of applications (door opening applications by proximity etc.)

2.- The number of packets transmitted during the connection.

With Bluetooth Low Energy, when you want to establish a connection all of the connection information is contained in a packet which is transmitted from the master to the slave. This information includes the FHSS map and other settings. This means that no additional negotiations are needed in order to begin sending useful data once the link has been established, which means less time which in turn means less consumption.

Also, when communicating between two devices with traditional Bluetooth, you lose time with packet synchronization and lag time, even though neither of the devices have anything to transmit. With Bluetooth Low Energy, the data packets have 1 bit of “more data” that indicates whether the sending device has packets to send or not and therefore if you need to keep your device “talking” or not.

Another very important feature is ACK packets. You send an ACK (a package without data, just to show that a packet has been received successfully) with normal Bluetooth for each packet sent. With Bluetooth Low Energy empty ACK data packets are only sent when it is really necessary. That way you don’t unnecessarily waste time and energy.

3.- The size of each packet.

The size of the data packet’s headers has decreased. The size of a standard Bluetooth header was made so that it could be sent in 210 us whereas with Bluetooth Low Energy is sent in 112 us (nearly half).

I’m interested, how can I work with a Bluetooth Low Energy module?

Well Bluegiga (distributed in Spain by Matrix) has just brought some Bluetooth Low Energy modules onto the market, specifically the BLE112 and BLED112 models.
Here’s a datasheet for you to look at. I will talk about them more thoroughly when my development kit arrives. As they are so new I still haven’t had the chance to have a SDK and play with them, hopefully I will soon.

I will only talk about the most important thing. Unlike other types of Bluegiga modules, these no longer use an internal CSR chip. They use a Texas Instruments chip, specifically the cc2540. Furthermore the module has an 8051-based processor (with 8Kb of RAM and 128Kb of FLASH) to embed user applications, so you don’t need to use it if you don’t want an external micro. It has 2 UART ports or SPI that we can connect directly to sensors, screens, digital and analog inputs/outputs, watchdog timer, hw AES128 encryption etc.  It’s a low-cost and complete module. As I said, I will talk about these modules when I have an SDK and have done a reliable test.

 

Tags:

Comments 5 Comments »