IntroductionBluetooth Low Energy (BLE) is an emerging

wireless transmission standard part of Bluetooth’s

Core Specifications v4.0 and aimed towards

applications which require small wireless

transceivers with low power consumption,

reduced bandwidth and simple connections. The

CC2540 chip comes with an accelerometer which

is manufactured by VTI and capable of detecting

motion along three axis.

Materials and methodsBy default, the drivers supplied by TI activate the

±2g range; however, it can also work with a ±8g

range and in free fall mode. It has a sensitivity of

56/14 counts per g, resolution of 18/ 71 mg. We

have designed GUI so that the users can turn

on/off accelerometer and choose the axis that

they want to measure. The device operates in an

interrupt type protocol, these interrupt messages

are referred to as notifications because they are

only sent back from the Keyfob to the dongle

when new data is available to be sent. The value

then needs to be interpreted from a byte to g

values. The Keyfob reads the data from the

accelerometer every 10ms.

Area n = (Sample n + (Sample n – Sample n-1 )/2 ) *T

Formulas to obtain the velocity and position;

• Velocity[1] = Velocity[0] + ((Acceleration[0] + Acceleration

[1])/2)*0.01

• Position[1] = Position[0] + ((Velocity[0] +

Velocity[1])/2)*0.01

ConclusionsLimitation

1) The device has to be moved fast so that

error percentage becomes smaller.

2) The device cannot differentiate between

tilted and translation movement.

3) Testing conditions are far from ideal.

Future Work

1) The accelerometer will be installed into a ball,

therefore the motion will be fast enough to make

the error percentage small

2) The accelerometer will be combined with

the gyroscope so that the device can

differentiate between tilted and translation

movement.

Tracking Position by Using Bluetooth Low Energy (BLE)

Texas Instruments CC2540 Development KitMohd Hazeeq Hanafi, Thanh Ngon Tran and Tho Le - Ngoc

Department of Electrical & Computer Engineering, Broadband Communication Research Lab, McGill University

Fig 2. Offset Calibration

Fig. 4a). Acceleration, Fig. 4b). Velocity, Fig. 4c). Position

Fig 4a) is the graph of acceleration; we have set

certain direction that the acceleration will increase

first then decrease. Fig 4b) velocity is the

integration of acceleration graph, it increases

(positive area) then decreases (negative area)

Fig 4c) position will always increase as the area

below velocity graph is all positive.

Future Applications

Fig. 1. These are the

CC2540 Keyfob board,

CC2540 USB Dongle

and Debugger

Results

SOFTWARE DESIGN CONSIDERATIONS :

1) Signal is not noise free, so we implement

moving average filter to filter the signal.

2) Real value of acceleration is sampled

acceleration minus calibration value

-4

-3

-2

-1

0

1

2

3

4

1 6

11

16

21

26

31

36

41

46

51

56

61

66

71

76

81

86

91

96

101

106

111

116

121

126

131

136

141

146

151

acc

(m

/s^

2)

Samples

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1 6

11

16

21

26

31

36

41

46

51

56

61

66

71

76

81

86

91

96

10

1

10

6

111

11

6

12

1

12

6

13

1

13

6

14

1

14

6

15

1

15

6

Vel

oci

ty (

m/s

)

Samples

0

0.05

0.1

0.15

0.2

0.25

1 6

11

16

21

26

31

36

41

46

51

56

61

66

71

76

81

86

91

96

10

1

10

6

111

11

6

12

1

12

6

13

1

13

6

14

1

14

6

15

1

Posi

tion

(m)

Samples

Actual Distance(cm) Result

Distance(cm)

Error

Percentage

(%)

X 24.0 23.13 3.6

Y 27.5 27.13 1.35

Z 19.0 19.9 4.7

2DX = 21

Y = 30

X = 20.21

Y = 28.57

X = 3.76

Y = 4.76

We’ll combine the accelerometer and

gyroscope so that we can track the balls

position in 6 degree of freedom.

We can also add this application to our

medical sensors so that we can detect if

the patient is falling.

We can add this application to video

game such as Wii, plus with ultra low

power consumption it’ll be great

prospect for future market.

Table 1

Fig. 3a) .GUI

References- Freescale Semiconductor Application Note,

AN3397 REV 0, 02/2007

- CMA300 data sheet from VTI Technologies,

Doc Nr. 8281000A.04

Fig 3b). 3D Display

4a)

4b)

4c)