User's Guide

www.lm-technologies.com

LM074 SPP with GAP Central Application v1.1

6. Simple Secure Pairing between LM074 and remote

device

This section describes the indication messages given by the LM074 module

during the pairing procedure. It also covers the AT commands that a user will

need to provide as per the settings of DPIN, MITM and IOTYPE.``

The LM074 uses BT2.1 security supporting the dynamic PIN, but is also

compatible with BT2.0 devices which shares fixed PIN during the pairing

procedure.

6.1 Pairing of LM074(BT2.1) with BT2.0 devices

Here the BT2.0 device is treated as LM Technologies’ LM048 device, with

firmware version 6.57. When the LM074 has DPIN as DPIN=OFF, it is

compatible with BT2.0 devices. When DPIN=OFF, the module does not

care about MITM, IOTYPE settings.

When DPIN is OFF, module uses PIN during the pairing procedure with

remote devices. Default PIN is 1234, users can change this to numeric

only, Alpha only or alphanumeric.

As per Bluetooth standards, maximum of 16 characters are allowed in PIN

setting.

6.1.1 If LM074 has setting DPIN=OFF

i. When the pairing procedure is started on the LM074, it will show

the indication message with the BD-Address of remote device e.g

“IND*:PAIR=00126f357215”.

ii. The user shall provide accept/reject response to this indication as

“AT*PAIR=00126f357215,accept” or

“AT*PAIR=00126f357215,reject”.

iii. LM074 uses its fixed PIN.

iv. If the fixed PIN of LM074 is same as the other device pairing is

successful.

v. After completing the pairing procedure, the LM074 indicates the

status of pairing to user e.g. “IND*:PAIR=OK,00126f357215” or

“IND*:PAIR=FAIL,00126f357215” .

vi. If the fixed PIN of LM074 is not same as other device pairing fails.

6.2 Pairing of LM074 (BT2.1) with BT2.1 devices

Here the BT2.0 device is treated as LM Technologies’ LM048 device with

firmware version 6.19. The passkey used during the pairing procedure is

dependent on the IO-type setting on the LM074.