BTM410/411
Bluetooth
®
AT Data Module
25
www.lairdtech.com
Laird Technologies
AT COMMAND SET
REFERENCE
10.
Known SSP Issues
a.
General Bonding (automatic pairing on link setup if devices have not been paired previously)
does not work with legacy devices (BT2.0 and earlier). If the remote device is BT2.0 or earlier,
initiate dedicated bonding (AT+BTW<BdAddr>) prior to connection establishment.
b.
Outgoing General Bonding (automatic pairing on link setup if devices have not been paired
previously) with MITM does not work with two BTM devices, because any UART input on the
initiating device is not accepted until the link has been established. Workaround: initiate
dedicated bonding (AT+BTW<BdAddr>) prior to connection establishment.
c.
If the link key of previously paired devices is not available any more in the remote device but
still available in the trusted device list (TDL) of the local device (query by AT+BTT?), pairing will
fail. In that case remove the device address from the local TDL using AT+BTD<BdAddr> and
reinitiate pairing from the local device (AT+BTW<Bd_addr>)
AT Commands for Legacy Pairing
1.
AT+BTW<bd_addr> {Initiate Pairing}
Provided the remote device is a Bluetooth 2.0 device or earlier and legacy pairing is not disabled
(S323 = 0), this command is used to initiate legacy pairing with the device with <bd_addr>. Legacy
pairing refers to the mechanism of entering an identical PIN key on both ends. If the PIN is required
(if not set earlier by AT+BTK=”<PIN>”), asynchronous indications will be sent to the host in the form
PIN? <bd_addr> where the address confirms the device with which the pairing is to be performed.
To supply a PIN, use the AT+BTK command.
For a successful pairing, the link key is stored in a volatile cache which is overwritten every time a
new pairing is initiated using this command. If S register 325=1, the link key is automatically saved
to the non-volatile trusted device list. Otherwise (S325=0) the link key can be added to the trusted
device list by AT+BTT. Please refer to below under AT Commands managing Trusted Devices for
further AT commands related to trusted device list.
The “OK” response is sent immediately on receipt of the AT+BTW command. On pairing completion,
an unsolicited message will be sent to the host which will be in the form PAIR n <bd_addr>.
If AT+BTI or AT+BTP or AT+BTG or AT+BTQ or ATD is issued between the AT+BTW command and the
subsequent PAIR asynchronous response, then an ERROR response will be sent to those commands
as the device is not in a mode from where such commands can be actioned.
Response:
<cr,lf>OK<cr,lf>
2.
AT+BTK=”<string>”
{Set Passkey}
This command is used to provide a PIN passkey. The PIN is stored in non-volatile memory for future
use. If this command is used as response to a “PIN? 12345678” asynchronous message, the PIN
provided by this command will not be stored in non-volatile memory.
Specifying an empty string deletes the PIN from the non-volatile memory. The string length must be
in the range 0 to 8, otherwise an error will be returned.
Response:
<cr,lf>OK<cr,lf>
Summary of Contents for BTM410
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