TDK Module blu2i User manual

blu2i Module
User Guide
The information contained in this document is subject to change without notice. TDK Systems Europe makes no warranty of
any kind with regard to this material including, but not limited to, the implied warranties of merchant ability and fitness for a
particular purpose. TDK Systems Europe shall not be liable for errors contained herein or for incidental or consequential
damages in connection with the furnishing, performance, or use of this material.
© Copyright 2004 TDK Systems Europe Limited.
All rights reserved.
This document contains information that is protected by copyright. All rights reserved. No part of this document may be
photocopied, reproduced, or translated to another language without the prior written consent of TDK Systems Europe.
Other product or company names used in this publication are for identification purposes only and may be trademarks of their
respective owners.
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Contents
BEFORE YOU BEGIN.................................................................................................................................................................... 3
SAFETY GUIDELINES ................................................................................................................................................................... 3
RF APPROVALS .......................................................................................................................................................................... 3
1FUNCTIONS ...................................................................................................................................................................... 4
2APPLICATION INTERFACE ............................................................................................................................................. 5
2.1 SERIAL INTERFACE......................................................................................................................................................... 5
2.2 POWER SUPPLY............................................................................................................................................................. 6
2.3 POWER-ON-RESET (POWER CYCLING AND BROWN OUT CONSIDERATIONS)..................................................................... 6
2.4 SPI BUS ........................................................................................................................................................................ 8
2.5 PARALLEL PIO PORT ..................................................................................................................................................... 8
2.6 PCM CODEC INTERFACE................................................................................................................................................ 8
3ELECTRICAL SPECIFICATION OF THE INTERFACE .................................................................................................... 9
3.1 ELECTRIC CHARACTERISTICS ....................................................................................................................................... 11
4PHYSICAL CHARACTERISTICS.................................................................................................................................... 13
4.1 MECHANICAL DIMENSIONS............................................................................................................................................ 13
4.2 MOUNTING THE BLU2IMODULE ONTO THE APPLICATION PLATFORM ................................................................................. 14
4.3 BOARD TO BOARD CONNECTOR.................................................................................................................................... 14
5ELECTRICAL AND RADIO CHARACTERISTICS.......................................................................................................... 16
5.1 ABSOLUTE MAXIMUM RATINGS ...................................................................................................................................... 16
5.2 OPERATING TEMPERATURES......................................................................................................................................... 16
5.3 POWER CONSUMPTION ................................................................................................................................................ 16
5.4 LOW POWER MODES USING SNIFF ................................................................................................................................ 19
5.5 RF PERFORMANCE ....................................................................................................................................................... 21
5.5.1 Transmit Power ............................................................................................................................................. 21
5.5.2 Receive Sensitivity ........................................................................................................................................ 21
5.5.3 Range ............................................................................................................................................................ 21
5.5.4 Performance against Temperature................................................................................................................ 22
5.6 RELIABILITY ................................................................................................................................................................. 23
6RS232 MODEM SIGNALS............................................................................................................................................... 24
6.1 MODEM SIGNALLING OVER BLUETOOTH......................................................................................................................... 25
6.2 BREAK SIGNAL ON RX LINE ......................................................................................................................................... 25
6.3 RESET ......................................................................................................................................................................... 26
7PURE CABLE REPLACEMENT MODE.......................................................................................................................... 27
7.1 DATA CABLE ................................................................................................................................................................ 27
7.2 AUDIO CABLE............................................................................................................................................................... 28
7.3 MODEM CONTROL AND STATUS SIGNALS ...................................................................................................................... 29
8GETTING STARTED ....................................................................................................................................................... 30
8.1.1 Two blu2i Modules.......................................................................................................................................... 30
8.1.2 One blu2i Module and Bluetooth PC using TDK’s USB Adaptor or PC Card................................................. 31
8.2 FACTORY DEFAULT MODE ............................................................................................................................................ 32
8.3 SOFTWARE .................................................................................................................................................................. 32
APPENDIX A ................................................................................................................................................................................ 34
EUROPE –EU DECLARATION OF CONFORMITY .......................................................................................................................... 34
FCC AND INDUSTRY CANADA STATEMENTS ............................................................................................................................... 34
APPENDIX B ................................................................................................................................................................................ 35
ESD (ELECTROSTATIC DISCHARGE).......................................................................................................................................... 35
ADDITIONAL STATEMENT ........................................................................................................................................................... 35
WARRANTY ................................................................................................................................................................................. 36
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Before You Begin
Congratulations on your purchase of the TDK Systems blu2i Module.
The Module is designed to be built into a device and to provide a simple,
low cost Bluetooth interface. The module is designed to integrate with a
wide range of applications and platforms with a simple electrical and
software interface using AT commands.
This guide aims to provide all the electrical and mechanical information
needed to design applications using the blu2i Module. A separate
document, blu2i Module - AT Command Set, outlines the protocol for the
software interface.
Safety Guidelines
The following safety precautions must be observed during all phases of
the operation, usage, service or repair of any application incorporating
this Bluetooth Module. Manufacturers of the RF equipment are advised
to convey the following safety information to users and operating
personnel and to incorporate these guidelines into all manuals supplied
with the product. Failure to comply with these precautions violates safety
standards of design, manufacture and intended use of the product. TDK
Systems assumes no liability for customer failure to comply with these
precautions.
RF Approvals
The blu2i Module is listed as a Bluetooth Product in terms of the
Bluetooth SIG Program Reference Document (PRD). This means that it
can be integrated into end products without further testing or approval
listing. The manufacturer must state the TDK part number and product
reference in his literature in order to meet the requirements of the
Bluetooth and regulatory approvals.
A list of the countries where the module is approved will be provided by
TDK Systems as required. As a minimum the product is listed in Europe,
Scandinavia and USA. TDK Systems assumes no liability for customer
failure to comply with national RF approvals.
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Functions1
The blu2i Module contains a complete Bluetooth interface and requires
no further hardware to implement full Bluetooth communication. The
module has an integrated, high performance antenna together with all
RF and Baseband circuitry, it interfaces to the host over a straight
forward serial port using AT commands. The module runs specific
firmware within the Virtual Processor that includes a serial Port Profile
and AT command interpreter. The module can be configured so that it
can be attached to a ‘dumb’ terminal or attached to a PC or PDA for
cable replacement applications.
The module provides access to 5 General I/O lines and 2 analogue I/O
lines to provide Bluetooth connection to simple devices such as switches
or LEDs without requiring any processing at the module end.
blu2i Module features at a glance:
Feature Implementation
Bluetooth Transmission Class 1
Frequency 2.400 – 2.485Ghz
Minimum Transmit Power +0dBm
Maximum Transmit Power +6dBm
Receive Sensitivity Better than -85dB
Antenna Gain +2dBi
Range (see Section 6.1.3) Up to 100 metres, free space
Data Transfer Rate Up to 200Kbps
Physical size 24 x 69 x 5 mm
Weight 8g
Fully Bluetooth pre-qualified Bluetooth 1.1 PRODUCT listing
Current consumption Less than 36mA during data
transfer
Temperature Range -20°C to +75°C
Audio Audio can be transferred over
SCO channels through the PCM
interface at 64Kbps
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Application Interface2
The blu2i Module is equipped with a 40-pin 0.5mm pitch board to board
connector that connects to the application platform. Electrical and
mechanical characteristics of the board-to-board connector are specified
in Chapter 3.
•Serial interface (see Section 3.0)
•Electrical specification of the interface (see Section 3.1)
2.1 Serial Interface
UART_TX, UART_RX, UART_RTS and UART_CTS form a conventional
asynchronous serial data port. The interface is designed to operate
correctly when connected to other UART devices such as the 16550A.
The signalling levels are nominal 0V and 3.3V and are inverted with
respect to the signalling on an RS232 cable. The interface is
programmable over a variety of bit rates; no, even or odd parity; stop bit
and hardware flow control. The default condition on power-up is pre-
assigned in the external Flash. Two-way hardware flow control is
implemented by UART_RTS and UART_CTS. UART_RTS is an output
and is active low. UART_CTS is an input and is active low. These
signals operate according to normal industry convention.
By writing different values to the S register the UART_RI can be
continuously polled to detect incoming communication. The UART_RI
signal serves to indicate incoming calls.
UART_DSR is an active low input. It should be connected to DTR output
of the host. When the module is running in high speed mode (See
definition for S Register 512), this pin should be asserted by the host to
ensure connection is maintained. A deassertion is taken to mean that the
connection should be dropped, or an online command mode is being
requested.
The module communicates with the customer application using the
following signals:
RS-232
•Port /TXD @ application sends data to the module’s UART_RX
signal line
•Port /RXD @ application receives data from the module’s
UART_TX signal line
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blu
2i
Module Application
UART_TX /RXD
UART Interface RS232 Interface
UART_RX /TXD
UART_CTS /RTS
UART_RTS /CTS
UART_DTS /DTR
UART_DTR /DSR
UART_DCD /DCD
UART RI
/
RING
Figure: UART interfaces
2.2 Power Supply
The power supply for the blu2i Module has to be a single voltage source
of Vcc= 3.6V to 6V. It must be able to provide sufficient current in a
transmit burst which can rise to 65mA.
The module includes regulators to provide local 3.3V and 1.8V. These
rails are accessible on connector J2 for monitoring.
Power (Vcc) should be provided via the board-to-board connector Pin 29
on J2.
Section 5.3 details the power consumption in different modes.
2.3 Power-On-Reset (Power Cycling and Brown Out
considerations)
The Module is provided with an active high reset pin (Hirose 40 way
DF12C connector pin 13). This pin whose electrical specification may be
found in section 3.3 is internally pulled to ground through a 10KΩ
resistor. Upon the application of power, the Power On Reset circuit built
into the module will ensure that the unit starts correctly.
However the module utilises a split rail design with some components
working at 3V3 and some at 1V8. Under certain extreme conditions, for
6 of 36

example when the supply voltage to the module experiences a Brown-
Out (momentary dip in the supply voltage level), or a rapid power cycle
i.e. the power is switched off and then on within 1second, there is a
possibility that the module can enter an unknown state of operation.
It is strongly recommended that the application hardware onto which the
module is mounted provides a Power-On-Reset circuit with a Brown-Out
detection capability. This will guarantee that under all circumstances the
module will operate in a known state.
A device such as the Maxim MAX6382XR26D3-T would be a suitable
part to perform the reset – it has an active high push-pull output, a 2.63V
detection threshold, and an active reset period of 140ms. This
inexpensive device is available in a SC70-3 package (2.2mm x 2.4mm)
and requires no additional components to operate. The device is used to
monitor the output of the voltage regulator on the module (through pin
27), and drives the Reset line (pin13) high when the supply voltage falls
out of tolerance. The schematic below illustrates its use.
blu2i Module
Pin27
Pin13
BC02 3V3
BC02 MRESET
GND
Please note that this 3V3 is the output of
the 3V3 regulator on the blu2i Module and
should not be connected to any other
supplies on the application hardware.
GND
10K
Vcc
ResetGnd
MAX6382
1
3
2
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2.4 SPI Bus
The module is a slave device that uses terminals SPI_MOSI, SPI_MISO,
SPI_CLK and SPI_CSB. This interface is used for program firmware
update.
Note: The designer should be aware that no security protection is built
into the hardware or firmware associated with this port, so the terminals
should not be permanently connected in a PC application.
2.5 Parallel PIO Port
Five lines of programmable bi-directional input/outputs (I/O) are
provided. GPIO[1:5] are powered from VCC. The mode of these lines
can be configured and the lines are accessed via S Registers 621 to
625.
Auxiliary functions available via these pins include an 8-bit ADC and an
8-bit DAC. This function is not implemented at this time.
2.6 PCM Codec Interface
PCM_OUT, PCM_IN, PCM_CLK and PCM_SYNC carry up to three bi-
directional channels of voice data, each at 8K samples/s. The format of
the PCM samples can be 8-bit A-law, 8-bit µ-law, 13-bit linear or 16-bit
linear. The PCM_CLK and PCM_SYNC terminals can be configured as
inputs or outputs, depending on whether the module is the Master or
Slave of the PCM interface.
The blu2i module is compatible with the Motorola SSI TM interface and
interfaces directly to PCM audio devices including the following:
•Qualcomm MSM 3000 series and MSM 5000 series CDMA
baseband devices
•OKI MSM7705 four channel A-law and µ-law CODEC
•Motorola MC145481 8-bit A-law and µ-law CODEC
•Motorola MC145483 13-bit linear CODEC
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Electrical specification of the interface3
The Hirose DF12C board to board connector on the module is a 40 way
double-row receptacle. The pin allocation is as follows:
Pin Signal Description Pin Signal Description
1 Analogue 0 1.8v Max 2 GPIO1 I/O for Host
3 Analogue 1 1.8v Max 4 GPIO2 I/O for Host
5 SPI_MISO SPI bus serial
O/P
6 UART_RI ‘Ring’ Input or
Output
7 SPI_CSB SPI bus chip
select I/P
8 UART_DCD Input or Output
9 SPI_CLK SPI bus clock
I/P
10 UART_DSR Input
11 GND 12 GPIO3/UART
_DTR
I/O for Host
13 RESET Reset I/P 14 GPIO4 I/O for Host
(Right LED)(2)
15 GND 16 GPIO5 I/O for Host (Left
LED) (2)
17 SPI_MOSI SPI bus serial
I/P
18 GND
19 UART_CTS Clear to Send
I/P
20 PCM_CLK PCM Clock I/P
21 UART_TX Transmit Data
O/P
22 PCM_IN PCM Data I/P
23 UART_RTS Request to
Send O/P
24 PCM_SYNC PCM Sync I/P
25 UART_RX Receive Data
I/P
26 PCM_OUT PCM Data O/P
27 VCC_3V3 3.3V Output
(Note 3)
28 N/C
29 VCC_5V 3.6V < VIN <
6.0V
30 GND
31 N/C 32 RESERVED Do not connect
33 N/C 34 RESERVED Do not connect
35 N/C 36 GND
37 N/C 38 GND
39 VCC_1V8 1.8V Output
(Note 3)
40 N/C
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Notes:
•UART_RX, UART_TX, UART_CTS, UART_RTS, UART_RI,
UART_DCD and UART_DSR are all 3.3v level logic. For example,
when RX and TX are idle they will be sitting at 3.3V. Conversely
for handshaking pins CTS, RTS, RI, DCD, DSR a 0v is treated as
an assertion.
•Pin 6 (UART_RI) is active low. It is normally 3.3v. When a remote
device initiates a connection, this pin goes low. This means that
when this pin is converted to RS232 voltage levels it will have the
correct voltage level for assertion.
•Pin 8 (UART_DCD) is active low. It is normally 3.3v. When a
connection is live this pin is low. This means that when this pin is
converted to RS232 voltage levels it will have the correct voltage
level for assertion.
•Pin 10 (UART_DSR) is an input, with active low logic. It should be
connected to the DTR output of the host. When the blu2i Module is
in high speed mode (See definition for S Register 512), this pin
should be asserted by the host to ensure that the connection is
maintained. A deassertion is taken to mean that the connection
should be dropped, or an online command mode is being
requested.
•The GPIOn pins can be accessed using S Registers 621 to 625
•GPIO4 and GPIO5 are also connected to LEDs on the module. If
these I/O pins are set for input, then the LED will be driven by the
host and appropriate drive current requirements must be satisfied.
By default GPIO4 is used to drive the right LED which indicates
connection status. A Logic 1 switches on the LED.
•Analogue 0 and 1 should not exceed 1.8v and S Registers 7xx are
used to access them.
•GPIO3 is used for DTR output (active low).
10 of 36

3.1 Electric Characteristics
Function Signal Name Pin No I/O Signal level Comments
Power
Supply
Vcc 29 I 3.6V to 6V Ityp = 50mA
GND 11, 15,
18, 30,
36, 38
6 Ground
terminals to
be attached
in parallel
RS232
Interface
UART_TX 21 O VOLmax=0.2V
VOHmin=2.8V
UART_RX 25 I
VILmax=0.8V
VIHmin=2.10V
VIHmax=3.7V
UART_CTS 19 I
VILmax=0.8V
VIHmin=2.10V
VIHmax=3.7V
UART_RTS 23 O
VOLmax=0.2V
VOHmin=2.8V
UART_DSR 10 I
VILmax=0.8V
VIHmin=2.10V
VIHmax=3.7V
UART_DTR 12 O
VOLmax=0.2V
VOHmin=2.8V
Shared with
GPIO3
UART_RI 6 I or O
O/P : VOLmax=0.2V
VOHmin=2.8V
I/P : VILmax=0.8V
VIHmin=2.10V
VIHmax=3.7V
Direction
may be
programme
d.
UART_DCD 8 I or O
O/P : VOLmax=0.2V
VOHmin=2.8V
I/P : VILmax=0.8V
VIHmin=2.10V
VIHmax=3.7V
Direction
may be
programme
d.
External
Power
Supply
VCC_1V8 39 O 1.8V typical For
monitoring
only. No
current
source
VCC_3V3 27 O 3.3V typical
SPI Bus SPI_MOSI 17 I VILmax=0.8V
VIHmin=2.10V
VIHmax=3.7V
Used to
reprogram
Flash
SPI_MISO 5 O
VOLmax=0.2V
VOHmin=2.8V
SPI_CSB 7 I
VILmax=0.8V
VIHmin=2.10V
VIHmax=3.7V
SPI_CLK 9 I
VILmax=0.8V
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VIHmin=2.10V
VIHmax=3.7V
PCM
Interface
PCM_CLK 20 I or O
O/P : VOLmax=0.2V
VOHmin=2.8V
I/P : VILmax=0.8V
VIHmin=2.10V
VIHmax=3.7V
If unused
keep pins
open
PCM_IN 22 I
VILmax=0.8V
VIHmin=2.10V
VIHmax=3.7V
PCM_SYNC 24 I or O
O/P : VOLmax=0.2V
VOHmin=2.8V
I/P : VILmax=0.8V
VIHmin=2.10V
VIHmax=3.7V
PCM_OUT 26 O
VOLmax=0.2V
VOHmin=2.8V
Reserved BC02
USB D-
32 I
VILmax =0.3vdd_pads
VIHmin =0.7cdd_pads
Normally
inactive.
Pull to GND
through 10K
BC02
USB D+
34 I
VILmax =0.3vdd_pads
VIHmin =0.7cdd_pads
GPIO GPIO 1 - 5 2,4,12,
14,16
I or O O/P : VOLmax=0.2V
VOHmin=2.8V
I/P : VILmax=0.8V
VIHmin=2.10V
VIHmax=3.7V
Analog
I/O
AIO_0,
AIO_1
1, 3 I/O Vout max=VDD_PIO-
.3
Vout min=VDD_PIO
Reset RESET 13 I VDD falling
threshold=1.5V typ
VDD rising
threshold=1.6V typ
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Physical Characteristics4
4.1 Mechanical Dimensions
13 of 36

4.2 Mounting the blu2i Module onto the application
platform
There are many ways to properly install the Module in a host device. An
efficient approach is to mount the PCB to a frame, plate, rack or chassis.
Fasteners can be M1.8 or M2 screws plus suitable washers, circuit
board spacers, or customized screws, clamps, or brackets in 2.2mm
diameter holes. Note that care should be taken to ensure the head of the
fixing does not interfere with the circuit. Nylon fixings are recommended.
In addition, the board to board connection can also be utilized to achieve
better support.
The antenna (Brown square component on top side of PCB) must not be
influenced by any other PCBs, components or by the housing of the host
device. The proximity of the antenna to large metallic objects can affect
the range and performance of the system. Designers should carefully
consider the location of the module and the type of enclosure material
that is used.
To prevent mechanical damage, be careful not to force, bend or twist the
module. Be sure it is positioned flat against the host device.
4.3 Board to Board Connector
This section provides specifications for the 40 way board-to-board
connector which serves as physical interface to the host application. The
receptacle assembled on the blu2i Module is type Hirose DF12C.
Item Part number Stacking height HRS number
Receptacle
on Module
DF12C-40DS-
0.5V(81)
3.5mm - 5mm CL537-0007-7-
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Mating headers from Hirose are available in different stacking heights.
Details are available at:
http://www.hirose.co.jp/cat2002e/500/e53700036.pdf
Item Part number Stacking height HRS number
Headers
DF12 series
DF12(3.5)-40DP-
0.5V(81)
3.5mm CL537-0032-4-
**
DF12(4.0)-40DP-
0.5V(81)
4.0mm CL537-0057-5-
**
DF12(5.0)-40DP-
0.5V(81)
5.0mm CL537-0157-0-
**
Note: The headers listed above are without boss and metal fitting.
Electrical and mechanical characteristics of the Hirose DF12C
connector:
Parameter Specification (40 pin Board to
Board connector)
Number of Contacts 40
Quantity delivered 2000 Connectors per Tape & Reel
Voltage 50V
Current Rating 0.5A max per contact
Resistance 0.05 Ohm per contact
Dielectric Withstanding Voltage 500V RMS min
Operating Temperature -45°C to +125°C
Contact Material phosphor bronze (surface: gold
plated)
Insulator Material PA , beige natural
Stacking height 3.0 mm; 3.5 mm; 4.0 mm; 5.0 mm
Insertion force 21.8N
Withdrawal force 1st 10N
Withdrawal force 50th 10N
Maximum connection cycles 50
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Electrical and radio characteristics5
5.1 Absolute Maximum ratings
Absolute maximum ratings for supply voltage and voltages on digital and
analog pins of the module are listed below. Exceeding these values will
cause permanent damage.
Minimum Maximum
Peak current of power supply 0mA 100mA
Voltage at digital pins -0.3V 3.7V
Voltage at POWER pin 3.3V 7V
5.2 Operating temperatures
Minimum Typical Maximum
Operating temperature -20°C 25°C +75°C
5.3 Power Consumption
The current drain from the Vcc power input line is dependent on various
factors. The three most significant factors are the voltage level at Vcc,
UART baud rate and the operating mode.
The hardware specification for the blu2i module allows for a voltage
range of 3.6 to 6.0v at Vcc. Tests have shown that there is no significant
difference in current draw when Vcc is 5 or 6V. Therefore the data
presented below, pertains to Vcc levels of 3.6 and 5v only. Tests have
shown that where power drain is an issue, it is best to keep Vcc at the
lower end of the range.
The UART baud rate has a bearing on power drain because as is normal
for digital electronics, the power requirements increase linearly with
increasing clocking frequencies. Hence higher baud rates result in a
higher current drain.
Finally with regards to operating mode the significant modes are; idle,
waiting for a connection, inquiring, initiating a connection and connected.
With connected mode, it is also relevant to differentiate between no data
16 of 36

being transferred and when data is being transferred at the maximum
rate possible.
The operating mode can best be described by stating the AT commands
required to enter that mode. In addition, there are certain S Registers
which have a direct impact on power consumption, which are described
next.
The blu2i Module has 2 LEDs which can be configured to display
connection status. One led is used to display connection status, while
the other is used to either display ‘Ring Indicate’ status or follow the
state of the incoming DSR line on the UART interface. Tests have shown
that these LEDs can consume up to 5.3mA which is more than double
the current draw when in Idle mode. Therefore S Registers 533 and 534
can be used to completely disable these indications.
Finally S Registers 508 to 511, which specify the page and inquiry scan
intervals and windows, can be used to adjust the average current drain
when in discoverable and or connectable modes. Registers 508 and 509
specify the interval and window for page scans and registers 510 and
511 specify the interval and window for inquiry scans. Register pairs
508/509 and 510/511 describe duty cycles when the blu2i module goes
into scan modes. It is while scanning that the highest current draw
occurs. The average current draw is determined by simple arithmetic
using the values stored in the 508/509 and 510/511 register pairs.
The operating modes described above are entered using AT commands
as follows
Idle On power up, with S Register 512 = 1
Wait for Connection AT+BTG (100% page scan duty cycle)
Discoverable Only AT+BTQ (100% inquiry scan duty cycle)
Connecting ATD
Connected No Data
Connected Max data transfer
All current consumption values in the table below assume that the
connection status indication functionality of the LEDs has been disabled
by setting S Registers 533 and 534 to 0.
All current values are in milliamps (mA).
17 of 36

Baud rate
9600 38400 115200 460800
3.6V 3.20 3.20 3.20 3.20Current per LED
5.0V 5.30 5.30 5.30 5.30
Baud rate
9600 38400 115200 460800
3.6V 1.60 1.80 1.96 3.00Idle Mode, S512=1
5.0V 2.00 2.10 2.30 3.40
3.6V 59.00 59.00 59.00 59.00Wait for Connection Or
Discoverable Mode,
AT+BTP
S508=S510=640,
S509=S511=320
5.0V 65.00 65.00 65.00 65.00
3.6V 2.75 2.94 3.10 4.12Wait for Connection Or
Discoverable Mode,
AT+BTP
S508=S510=1000,
S509=S511=11
5.0V 3.26 3.36 3.55 4.63
3.6V 50.00 50.00 50.00 50.00Inquiring Mode, AT+BTI
5.0V 54.00 54.00 54.00 54.00
3.6V 50.00 50.00 50.00 50.00Connecting Mode
(ATDxxx) 5.0V 54.00 54.00 54.00 54.00
3.6V 6.00 6.10 6.40 7.20Connected as Master
Mode (No Data Transfer)
Sniff NOT activated
5.0V 7.20 7.20 7.40 8.20
3.6V 21.50 22.50 24.50 32.50Connected as Master
Mode (Max Data
Transfer)
Sniff NOT activated
5.0V 24.50 26.00 28.00 36.00
Connected as Slave
Mode (No Data Transfer) 5.0V 32.00 33.00 33.50 34.00
Connected as Slave
Mode (No Data Transfer)
Sniff Enabled (AT&F1
setting)
5.0V 4.90
As can be seen, the current drain while waiting for a connection or
discoverable mode is about 30 times higher than in idle mode. This is
when the page/inquiry scan duty cycle is 100%. These modes give the
quickest response to a page or inquiry request from a remote peer.
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It is possible to reduce the duty cycle down to as low as 0.5% at the
expense of response time. The response time can be specified via S
Registers 508 and 510 for page and inquiry respectively, where the
worst case response time can be as high as 2.5 seconds. Then the duty
cycle can be varied by changing the value of S Registers 509 and 511
appropriately.
For example, if S Register 508 and 510 are both set to 1000ms and S
Register 509 and 511 are both set to 11ms then the duty cycle is
reduced to 1%, this means that average current drain at 5.0v will be 2%
of 65mA plus the normal idle mode current, that is, it is as low as
2.75mA. However, in this case, it can take up to 1 second to establish a
connection.
The connected state current consumption while a master or slave can be
considerably reduced by enabling Sniff mode, described in detail in the
next section.
5.4 Low Power Modes using Sniff
Bluetooth connections are master/slave in nature. A master sends
packets and a slave has to acknowledge that packet in the next timeslot.
Timeslots in Bluetooth are 625 microseconds wide. This implies that a
master will always know when packets will be sent and received, which
further means it is able to optimise power usage by switching on power
hungry circuitry only when needed.
A slave on the other hand does NOT have prior knowledge of when a
packet will be received and has to assume that a packet will be received
from a master on every receive slot. This means that it has to leave it’s
receiving circuitry on for most of the receive slot duration. The result of
this is high power consumption as illustrated in the power table above,
where a slave with no data transmission still consumes around 31mA
whereas a master consumes only 6mA.
This problem was identified very early in the evolution of Bluetooth
(especially since headsets spend all their time as a slave in a Bluetooth
connection) and it was solved by having a mode called Sniff, with
appropriate lower layer negotiating protocol.
Sniff mode during connection is basically an agreement between the
slave and its master that data packets will only be exchanged for N
timeslots every M slots. The slave can then assume that it will never be
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contacted during N-M slots, and so can switch its power hungry circuitry
off. The specification goes further by also specifying a third parameter
called ‘timeout’ (T) which specifies ‘extra’ timeslots that the slave will
agree to listen for after receiving a valid data packet. Put another way, if
a data packet is received by the slave, then it knows that it MUST carry
on listening for at least T more slots. If within that T slot time period
another data packet is received, then the timer is restarted. This
mechanism ensures low power consumption when there is no data
transfer – at the expense of latency. When there is a lot of data to be
transferred, it acts as if sniff mode were not enabled.
It is stated above that during sniff mode, a slave listens for N slots every
M slots. The Bluetooth specification states that a master can have up to
7 slaves attached to it with all slaves having requested varying sniff
parameters. It may therefore be impossible to guarantee that each slave
gets the M parameter it requested. In light of this, the protocol for
enabling sniff mode specifies that a requesting peer specify the M
parameter as a minimum and maximum value. This will allow the master
to interleave the sniff modes for all slaves attached.
For this reason, the sniff parameters are specified in TDK module via
four S registers. S Register 561 is used to specify ‘N’, S Register 562 is
used to specify ‘T’ and S Registers 563/564 are used to specify
minimum ‘M’ and maximum ‘M’ respectively. Although the specification
defines these parameters in terms of timeslots, the S register values
have to be specified in units of milliseconds and the firmware does the
necessary translation to timeslots.
Data Exhange
High Power Consumption
Low Power Consumption
M
Slots (Negotiated)
M
Slots (Negotiated)
N
Slots
N
Slots
N
Slots
T
Slots
T
Slots
T
Slots
T
Slots
T
Slots
Data Exchange
Data Exchange
Data Exchange
Data Exchange
Data Exchange
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