DVK-BTM521 Laird Technologies, DVK-BTM521 Datasheet - Page 19

• Manufacturer Part Number: DVK-BTM521
• Description: BT MM DEV KIT
• Manufacturer: Laird Technologies
• Type: Transceiver, Bluetoothr

Specifications of DVK-BTM521

• Frequency: 2.4GHz
• Interface Type: RS-232
• Processor Series: BTM521
• Silicon Manufacturer: Laird Technologies
• Kit Application Type: Communication & Networking
• Application Sub Type: Bluetooth
• Kit Contents: Development Board & Software Tools
• Features: Supports CSR
• Rohs Compliant: Yes
• For Use With/related Products: BTM521
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: DVK-BTM521

BTM520/521
Bluetooth
AT COMMAND SET
REFERENCE
19 www.lairdtech.com
®
Multimedia Plus Module
General S Registers
Please refer to Appendix, Table 4.1 for a list of supported S Registers.
The main purpose of S Registers is to make the device configuration persistent. All S Registers can be saved to
non-volatile memory by AT&W.
In some cases, an AT command and an S register exist for one and the same setting. In the majority of those
cases the AT command’s setting will be lost on next power cycle whereas the S register can be saved and is still
available after power cycle. This rule applies to many but not to all of those cases.
AT Commands for Inquiry
1. AT+BTI<devclass> {Inquire}
This will make the device perform an inquiry for delay seconds and max number of unique responses,
where delay is defined by S register 517 and max is specified by S register 518.
The <devclass> is an optional parameter where the value specifies either a six digit device class code or
a two digit major device class. If it is not specified, the value is taken from S register 516.
When <devclass> is six hexadecimal characters long, it specifies an AND mask which is used to filter
inquiry responses. When <devclass> is two hexadecimal characters long, it forces the inquiry to filter
responses to devices that match their major device class code to this value – which can only be in
the range 00 to 1F.
The response format to AT+BTI is defined by S Register 330 by bitmask. This is device address, device
class, friendly name, receiver strength indicator and extended inquiry data. Please refer to Figure 3.1
and Table 3.2.
For S330=1:
Response: <cr,lf>12346789012
<cr,lf>12345678914
<cr,lf>OK<cr,lf>
A Bluetooth inquiry process is such that for a single inquiry request a device could respond many times.
To ensure that an address is sent to the host only once for a particular AT+BTI, an array of addresses is
created at the start of each AT+BTI and is filled as responses come in. This array of addresses is stored
in dynamic memory and as such if the memory allocation fails then the inquiry procedure is aborted and
in that case an error response is sent to the host. To clarify, a single AT+BTI will never return the same
Bluetooth address more than once. But as long as the responding device is active, all AT+BTI commands
will always return it.
As the inquiry process is driven by randomness, it is not guaranteed that each discoverable device is
always found on the first attempt. Sometimes more than one inquiry processes might be necessary
to find a particular device. The probability also depends on the inquiry scanning intervals of the device
being searched for.
The inquiry process can be sped up if the friendly name is not required (flag not set in S330) as part of
the inquiry response or if a <dev_class> filter is used.
Although it is very convenient to have the friendly name displayed in the inquiry response, this option
can significantly reduce the performance of the inquiry process. Especially in areas with a large number
of discoverable Bluetooth devices it might become nearly impossible to find a particular device.
An optimal solution would be a first inquiry scan without friendly name and <dev_class> filter. In a
second run, the friendly name is queried by AT+BTF<BdAddr> for each device found.
Bit
Default
7
Reserved for future usage
0
Figure 3.1: S Register 330 controlling inquiry response format
6
0
5
0
4
EIRD
0
3
RSSI
0
2
FN
0
1
COD
0
0
ADR
1
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