The BTM410 and BTM411 Bluetooth
needs of developers who wish to add robust, short range Bluetooth data connectivity to their products. They
are based on the market leading Cambridge Silicon Radio BC04 chipset, providing exceptionally low power
consumption with outstanding range. They support the latest Bluetooth® Version 2.1 Specifi cation, providing
the important advantage of Secure Simple Pairing, which improves security and enhances the ease of use for
end customers.
With physical sizes as small as 12.5 x 18.0mm and best of class, low-power operation, these modules are the ideal
choice for applications where designers need both performance and minimum size. For maximum fl exibility in
systems integration, the modules are designed to support a separate power supply for I/O.
To aid product development and integration, Laird Technologies has integrated a complete Bluetooth protocol
stack within the modules, including support for the Bluetooth Serial Port Profi le. The modules are fully qualifi ed as
Bluetooth End Products, allowing designers to integrate them within their own products with no further Bluetooth
Qualifi cation. They can then list and promote their products on the Bluetooth website free of charge.
Future releases include support for the Bluetooth Health Device Profi le, making this module the ideal choice for
manufacturers who are developing Continua Health Alliance
compliant devices.
A comprehensive AT command interface is included, which simplifi es fi rmware integration. Combined with a low
cost developers kit, this ensures that the choice of Laird Technologies Bluetooth modules guarantees the fastest
route to market.
FEATURES AND BENEFITS
• Bluetooth® v2.1+EDR
• Adaptive Frequency Hopping to cope with interference
from other wireless devices
• Secure Simple Pairing support
• External or internal antenna options
• Comprehensive AT interface for simple programming
®
• Bluetooth
• Compact size
• Class 2 output – 4dBm
• Low power operation
• UART interface
• Multi-point support
• PCM and SCO for external codec
• GPIO lines under AT control
• Support for Serial Port Profi le
• Support for Health Device Profi le (Q3 ‘09)
• Wi-Fi co-existence
END Product Qualifi ed
®
modules from Laird Technologies have been designed to meet the
Bluetooth
Transmit ClassClass 2
Frequency2.402 – 2.480 GHz
Channels
Max Transmit Power
Min Transmit Power
Receive Sensitivity
RangeUp to 50 metres free space
Data Transfer RateUp to 300 kbps
External Antenna50 Ohm matched SMT pad – BTM410
Integrated Antenna (option)+0dBi multilayer ceramic – BTM411 (provisional)
Serial Interface
Baud Rate
Bits8
ParityOdd, even, none
Stop bits1 or 2
Default Serial parameters9600,n,8,1
LevelsSet by VDD_USB input
Modem ControlDTR, DSR, DCD, RI, RTS, CTS
I/O8 general purpose I/O pins
Support3 PCM Channels @ 64kbps
SCO ChannelsSupport SCO and eSCO
PCM Interface
Bluetooth StackV2.1 compliant. Fully integrated.
Profi les
Firmware UpgradeAvailable over UART
Connection Modes
®
Version 2.1+EDR
79 channels Frequency Hopping
Adaptive Frequency Hopping
+4 dBm at antenna pad – BTM410
+4 dBmi from integrated antenna – BTM411 (provisional)
-27 dBm at antenna pad – BTM410
-27 dBmi from integrated antenna – BTM411
(provisional)
-84dBm
RS-232 bi-directional for commands and data
16550 compatible
Confi gurable from 1,200 to 921,600bps Non-standard
baud rates supported
Confi gurable as master or slave
8 bit A-law
8 bit μ-law
13 bit linear
PCM Clock available when in slave mode
Point to point (cable replacement)
Multipoint – max 3 slaves
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5
Laird Technologies
BTM410/411
Bluetooth® AT Data Module
SPECIFICATIONS
CATEGORIESFEATUREIMPLEMENTATION
Command Interface
Current Consumption
Supply Voltage
Coexistence / Compatibility
Connections
Physical
Environmental
Approvals
Miscellaneous
Development Tools
AT Instructions set
Multipoint SoftwareSupports multiple connections
Data TransferTypically 32mA
Low Power Sniff ModeLess than 2.5mA
Supply3.0V – 3.3V DC
I/O1.7V – 3.3V DC (independent of Supply)
USB & UART1.7V – 3.6V DC (independent of Supply)
WLAN (802.11)
Interface Surface Mount Pads
External Antenna (BTM410)Pad for 50 Ohm antenna
Dimensions
Weight3 grams
Operating Temperature -30°C to +70°C
Storage Temperature-40°C to +85°C
BluetoothQualifi ed as an END product
FCC
CE & R&TTEMeets CE and R&TTE requirements
Lead freeLead-free and RoHS compliant
Warranty12 Months
Development Kit
Comprehensive control of connection and module operation
S Registers for non-volatile storage of parameters
2-wire and 3-wire hardware coexistence
schemes supported
Development board and software tools
DVK-BTM410 Dev Kit with BTM410 module fi tted
DVK-BTM411 Dev Kit with BTM411 module fi tted
www.lairdtech.com
6
Laird Technologies
BTM410/411
Bluetooth® AT Data Module
SPECIFICATIONS
PINSIGNALDESCRIPTION
1Unused
2GND
3UART_CTSClear to Send I/PVUSB
4UART_RXDReceive data I/PVUSB
5UART_RTSRequest to Send O/PVUSB
6UART_TXDTransmit data O/PVUSB
7GND
8SPI_CSBSPI bus chip select I/PVIO
9SPI_MISOSPI bus serial O/PVIO
10SPI_MOSISPI bus serial I/PVIO
11SPI_CLKSPI bus clock I/PVIO
12VDD_USBUSB & UART supply voltage
13VDD_IOI/O supply voltage
14VDD_INMain supply voltage
15GND
16PCM_INPCM clock I/PVIO
17PCM_SYNCPCM sync I/PVIO
18PCM_CLKPCM clock I/PVIO
19PCM_OUTPCM Data O/PVIO
20RESETModule reset I/PSee note 2
21GPIO5I/O for hostVIO
22GPIO3 / UART_DCDI/O for hostVIO
23GND
24Unused
25Unused
26Unused
27Unused
28GND
29ANT (BTM410)Antenna connection (50 ohm matched)
30GND
31Unused
32Unused
33Unused
34Unused
35Unused
36Unused
37Unused
38Unused
39Unused
40Unused
41GND
42GPIO2 / UART_RII/O for hostVIO
43GPIO9 /UART_ DTRI/O for hostVIO
44GPIO10 / UART_DSRI/O for hostVIO
45GND
46D-Not used for AT module variantsVUSB
47D+Not used for AT module variantsVUSB
48GPIO7I/O for hostVIO
49GPIO6I/O for hostVIO
50GPIO4I/O for hostVIO
VOLTAGE
SPECIFICATION
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7
Note: 1. Unused pins may have internal connections and must not be connected.
2. Reset input is active low. Input is pulled up to VDD_IN via 22k. Minimum reset pulse width is 5ms.
This document describes the protocol used to control and confi gure the BT Data Bluetooth device.
The protocol is similar to the industry standard Hayes AT protocol used in telephony modems which is
appropriate for cable replacement scenarios, as both types of devices are connection oriented. The telephony
commands have been extended to make the device perform the two core actions of a Bluetooth device, which
is make/break a connection and Inquiry. Many other AT commands are also provided to perform
ancillary functions, such as, pairing, trusted device database management and S Register maintenance.
Just like telephony modems, the device powers up in an unconnected state and will only respond via
the serial interface. In this state the device will not even respond to Bluetooth Inquiries. Then, just like
controlling a modem, the host can issue AT commands which map to various Bluetooth activities. The
command set is extensive enough to allow a host to make connections which are authenticated and/or
encrypted or not authenticated and/or encrypted or any combination of these. Commands can be saved,
so that on a subsequent power up the device is discoverable or automatically connects.
The device has a serial interface which can be confi gured for baud rates from 1200 up to 921600 (default
setting is 9600) and an RF communications end point. The latter has a concept of connected and unconnected
modes and the former will have a concept of command and data modes. This leads to the matrix of states
shown below.
RF UNCONNECTEDRF CONNECTED
Local Command ModeOKOK
Remote Command ModeILLEGALOK
Data ModeILLEGALOK
The combinations, ‘Data and RF Unconnected Mode’ and ‘Remote Command and RF Unconnected Mode’
do not make sense and will be ignored.
Navigation between these states is done using the AT commands which are described in detail in
subsequent sections.
www.lairdtech.com
9
Laird Technologies
BTM410/411
Bluetooth® AT Data Module
CONFIGURING
THE BTM410/411
AT COMMAND SET
Assumptions
The CSR (Cambridge Silicon Radio) Bluecore chipset in Laird Technologies devices is memory resource limited.
Therefore it is NOT proposed that there be full implementation of the AT protocol as seen in modems. The
claim made for this device is that it will have a protocol similar to an AT modem. In fact, the protocol is similar
enough so that existing source code written for modems, can be used with very little modifi cation with a Laird
Technologies device.
Therefore the following assumptions are made:
1. All commands are terminated by the carriage return character 0x0D, which is represented by the
string <cr> in descriptions below this cannot be changed.
2. All responses from the device have carriage return and linefeed characters preceding and
appending the response. These dual character sequences have the values 0x0D and 0x0A respectively
and shall be represented by the string <cr,lf>.
3. All Bluetooth addresses are represented by a fi xed 12 digit hexadecimal string, case insensitive.
4. All Bluetooth Device Class codes are represented by a fi xed 6 digit hexadecimal string, case insensitive.
Commands
This section describes all available AT commands. Many commands require mandatory parameters and some
take optional parameters. These parameters are either integer values, strings, Bluetooth addresses or device
classes. The following convention is used when describing the various AT commands.
<bd_addr>A 12 character Bluetooth address consisting of ASCII characters ‘0’ to ‘9’, ‘A’ to ‘F’ and ‘a’ to ‘f’.
<devclass>A 6 character Bluetooth device class consisting of ASCII characters ‘0’ to ‘9’, ‘A’ to ‘F’ and ‘a’ to ‘f’.
NA positive integer value.
MAn integer value which could be positive or negative, which can be entered as a decimal value or
in hexadecimal if preceded by the ‘$’ character. E.g. the value 1234 can also be entered as $4D2
<string>A string delimited by double quotes. E.g. “Hello World”. The “ character MUST be supplied as delimiters.
<uuid>A 4 character UUID number consisting of ASCII characters ‘0’ to ‘9’, ‘A’ to ‘F’ and ‘a’ to ‘f’.
1. ^^^ {Enter Local Command Mode}
When in data and connected mode, the host can force the device into a command and connected
mode so that AT Commands can be issued to the device. The character in this escape sequence is
specifi ed in the S2 register, so can be changed. In addition, the escape sequence guard time is
specifi ed by S Register 12. By default the guard time is set to 100 milliseconds. Please refer to Section 5: Dropping Connections for more related information.
In modems this escape sequence is usually “+++”. “^^^” is specifi ed to avoid confusion when the module is providing access to a modem.
Response: <cr,lf>OK<cr,lf>
2. !!! {Enter Remote Command Mode}
When in data and connected mode, the host can force the remote device into a command and
connected mode so that AT Commands can be issued to the device remotely. The escape sequence
guard time is specifi ed by S Register 12 and is the same as per the ^^^ escape sequence. By default the guard time is set to 100 milliseconds. The remote device issues ATO as normal to return to data
mode. (Refer to step 12)
For this command to be effective S Register 536 must be set to 1.
Response: <cr,lf>OK<cr,lf>
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10
Laird Technologies
BTM410/411
Bluetooth® AT Data Module
CONFIGURING
THE BTM410/411
3. AT
Used to check the module is available.
Response: <cr,lf>OK<cr,lf>
4. ATA {Answer Call}
Accept an incoming connection, which is indicated by the unsolicited string
<cr,lf>RING 123456789012<cr,lf> every second. 123456789012 is the Bluetooth address of the
connecting device.
Make a connection to device with Bluetooth address <bd_addr> and SPP profi le <uuid>. The <uuid> is an optional parameter which specifi es the UUID of the profi le server to attach to, and if not supplied then the default UUID from S Register 101 is used. As this is a device which utilises the RFCOMM
layer as described in the Bluetooth specifi cation, it necessarily implies that only profi les based on RFCOMM can be accessed.
If <U> is not specifi ed, then authentication is as per register 500, otherwise the connection will
be authenticated.
If <Y> is not specifi ed, then encryption is as per register 501, otherwise the connection will have
encryption enabled.
The timeout is specifi ed by S register 505.
Response: <cr,lf>CONNECT 123456789012<cr,lf>
Or <cr,lf>NO CARRIER<cr,lf>
Due to a known issue in the Bluetooth RFCOMM stack, it is not possible to make more than 65525
outgoing connections in a single power up session. Therefore if that number is exceeded, then the
connection attempt will fail with the following response:-
Response: <cr,lf>CALL LIMIT
Or <cr,lf>NO CARRIER<cr,lf>
In that case, issuing an ATZ to reset the device will reset the count to 0 and more connections
are possible.
The following RFCOMM based UUIDs are defi ned in the Bluetooth Specifi cation:-
www.lairdtech.com
11
PROFILE NAMEUUID
Serial Port0x1101
LAN Access Using PPP0x1102
Dialup Networking0x1103
IrMC Sync0x1104
OBEX Object Push0x1105
OBEX File Transfer0x1106
IrMC Sync Command0x1107
Headset0x1108
Cordless Telephony0x1109
Intercom0x1110
Fax0x1111
Audio Gateway0x1112
WAP0x1113
WAP_CLIENT0x1114
Laird Technologies
BTM410/411
Bluetooth® AT Data Module
CONFIGURING
THE BTM410/411
6. ATD<U><Y>L {Remake Connection}
Make a connection with the same device and service as that specifi ed in the most recent ATD command. The <UY> modifi ers are optional. An error will be returned if the ‘L’ modifi er is
specifi ed AND a Bluetooth address.
If both ‘L’ and ‘R’ modifi ers are specifi ed then an error will be returned.
Response: <cr,lf>CONNECT 123456789012 AE<cr,lf>
Or <cr,lf>NO CARRIER<cr,lf>
7. ATD<U><Y>R {Make Connection to peer specifi ed in AT+BTR}
Make a SPP connection with the device address specifi ed in the most recent AT+BTR command. The service is as specifi ed in S Register 101. The <UY> modifi ers are optional. An error will be returned if the ‘R’ modifi er is specifi ed AND a Bluetooth address.
If both ‘R’ and ‘L’ modifi ers are specifi ed then an error will be returned.
Response: <cr,lf>CONNECT 123456789012 AE<cr,lf>
Or <cr,lf>NO CARRIER<cr,lf>
8. ATEn {Enable/Disable Echo}
This command enables or disables the echo of characters to the screen. A valid parameter value will
be written to S Register 506.
E0Disable echo.
E1Enable echo.
All other values of n will generate an error.
Response: <cr,lf>OK<cr,lf>
Or
Response: <cr,lf>ERROR nn<cr,lf>
9. ATH {Drop Connection}
Drop an existing connection or reject an incoming connection indicated by unsolicited
RING messages.
Response: <cr,lf>NO CARRIER<cr,lf>
10. ATIn {Information}
This will return the following information about the Laird Technologies device.
I0The product name/variant.
I1The CSR fi rmware build number.
I2The Laird Technologies fi rmware build number. For internal use only.
I3The Laird Technologies fi rmware revision.
I4A 12 digit hexadecimal number corresponding to the Bluetooth address of the device.
I5The manufacturer of this device.
I6The maximum size of trusted device database.
I7The manufacturer of the Bluetooth chipset.
I8The chipset format.
I90 if not in a connect state and 1 if in a connect state.
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12
Laird Technologies
BTM410/411
Bluetooth® AT Data Module
CONFIGURING
THE BTM410/411
I11The reason why a “NO CARRIER” resulted in the most recent attempt at making an outgoing connection.
Where the response values are as follows:
0 = No prior connection
1 = Connection timeout
2 = Connection attempt cancelled
3 = Normal disconnection
4 = Peer device has refused connection
5 = Service profi le <uuid> requested not available on remote device
6 = Connection has failed
32 = ATH was entered
33 = Incoming connection aborted because too many rings
34 = Unexpected incoming connection
35 = Invalid address
36 = DSR is not asserted
37 = Call limit of 65531 connections has been reached
38 = Pairing in progress
39 = No link key
40 = Invalid link key
255 = Unknown Reason
I12The last ERROR response number.
I13The Sniff status is returned as follows:-
Response: <cr,lf>a:b,c,d,e<cr,lf>OK<cr,lf>
Where ‘a’ = 0 when not online and 1 when online and Sniff has been enabled, ‘b’ is the Sniff Attempt
parameter, ‘c’ is the Sniff timeout parameter, ‘d’ is the minimum sniff interval and ‘e’ is the maximum
sniff interval. All parameters ‘b’, ’c’, ’d’ and ‘e’ are given as Bluetooth slots which are 625 microseconds
long converted from values of S Registers 561, 562, 563 and 564 respectively.
I14The current boot mode (Only for fi rmware 1.18.0 and newer)
I15The maximum length of an AT command, including the terminating carriage return
(only for fi rmware 1.6.10 and newer)
I16The size of AT command input buffer
I20Returns the number of bytes pending to be sent in the rf buffer when a connection is up.
I33Version number of Multipoint application (Note: ATI is provided for compatibility in multipoint mode,
other AT commands are not available).
I42State information. Where the response values are as follows:
13 = NotOpen
14 = OpenIdle
15 = Ringing
16 = OnlineCommand
172 to 177 = waiting for connectable and/or discoverable where the lowest signifi cant digit equates to
the value stored in S Register 512 or 555.
Note when n=16, ATI9 will return 1.
I101The RSSI value in dBm. If a connection does NOT exist then a value of -32786 is returned. A value of 0
means the RSSI is within the golden range this is quite a large band, therefore RSSI is not always a useful
indicator. Use ATI111 instead which returns the bit error rate.
I111Returns LinkQual which in the CSR chipset is defi ned as BER (bit error rate). This returns a value which
is the number of bits in error out of 1 million. Hence a value of 0 is best, and larger values are worse.
As the value approaches 1000 (BER = 0.1%) it is an indication that the link is very bad and a large
number of Bluetooth packets are being lost.
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13
Laird Technologies
BTM410/411
Bluetooth® AT Data Module
CONFIGURING
THE BTM410/411
For recognised values of n. All other values of n will generate an error.
Response: <cr,lf>As Appropriate<cr,lf>OK<cr,lf>
Or
Response: <cr,lf>ERROR nn<cr,lf>
11. ATO {Enter Data Mode} (letter ‘o’)
Return to data mode. Assume that the module is in data mode after OK is received. Responds with an
error if there is no Bluetooth connection.
Response: <cr,lf> CONNECT 123456789012<cr,lf>
Or
Response: <cr,lf>ERROR nn<cr,lf>
12. ATSn=m {Set S Register}
As with modems, the Bluetooth module employs a concept of registers which are used to store
parameters, such as escape sequence character, inquiry delay time etc, as listed in detail below.
The value part ‘m’ can be entered as decimal or hexadecimal. A hexadecimal value is specifi ed via a ‘$’ leading character. For example $1234 is a hexadecimal number.
When S register values are changed, the changes are not stored in non-volatile memory UNTIL the
AT&W command is used. Note that AT&W does not affect S registers 520 to 525 or 1000 to 1010
as they are updated in non-volatile memory when the command is received.
REGISTER DEFAULT RANGECOMMENT
S01-1..15Number of RING indication before automatically answering an incoming
connection. A value of 0 disables autoanswer. If -1, then autoanswer on
one RING and do NOT send RING/CONNECT response to the host. This
emulates a serial cable replacement situation.
Setting values >= 0, resets S Register 504 to 0 and <0 forces 504 to 1.
If S0 <> 0 and S100 <> 0 then S0 must be < S100. If a value is entered
which violates this rule, then ERROR 29 is sent in response.
If S504 =1 then this register will return -1, regardless of the actual value
stored in non-volatile memory.
S20x5E0x20..0x7EEscape sequence character. It is not ‘+’ by default as a Bluetooth serial link
can be used to connect to a mobile phone which exposes an AT command set,
which will in turn use ‘+’ as default. So if both used ‘+’ there will be confusion.
0x5e is the character ‘^’.
S1210040..5000Escape sequence guard time in milliseconds, with a granularity of 20ms.
New values are rounded down to the nearest 20ms multiple
S100150..15Number of RING indications before an auto disconnection is initiated. A value
of 0 disables this feature.
If S0 <> 0 and S100 <> 0 then S0 must be < S100. If a value is entered which
violates this rule, then ERROR 29 is sent in response.
S101$1101 0..$ffffUUID of default SPP based profi le when not specifi ed explicitly in the
ATD command.
S10211Defi nes a set of bits masks for enabling profi le servers. Values can be ORed.
1 is the default and only value allowed for this module which enables Serial
Port Profi le
S10311..7Boot Mode on cold boot.
S126?0 .. 0xFFFFPrimer for changing to Multipoint mode
S127?0 .. 0xFFFF0x100 for At mode
0x200 for Multipoint mode
Other values are reserved
S50000..1Authentication for outgoing connections. Set to 1 to Enable Authentication.
S50100..1Encryption for outgoing connections. Set to 1 to Enable Encryption.
S50200..1Authentication for incoming connections. Set to 1 to Enable Authentication.
S50300..1Encryption for incoming connections. Set to 1 to Enable Encryption.
www.lairdtech.com
14
Laird Technologies
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