User's Guide

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LM074 SPP with GAP Central Application v1.1

3. LM074 GAP Central Role

This section describes the AT commands for the GAP Central role to initiate a

connection, pair, whitelist, or read/write data to a BLE peripheral device.

AT commands for the SPP role and generic device configuration are described in

section 4 “LM074 AT commands and Default configuration”.

Every command is terminated with “CR-LF”. The module will begin parsing the AT

command string after receiving the “CR-LF” sequence.

For every AT command issued by a user via UART the module responds with

OK/ERR.

If the user issues an incorrect AT command string (e.g. instead of "AT*Settings=?"

the user issues "AT*Setting=?"), or issues a correct AT command string but in an

invalid state (e.g. the user issues a connection command

"AT*CONN=001122334455" while the SPP-role is Slave), the module will respond

with ERR.

AT commands are used to enable or disable the GAP Central role of the module. By

default, this mode is disabled and the module only initiates the SPP functionality. To

enable GAP Central functions, use the AT command AT*ENBGAP=ON. The module

will perform a soft reset and initialize itself with both SPP and GAP Central functions

initialized. When the module has the GAP Central role disabled, for every AT

command of GAP Central functionality or settings, module will respond with “ERR”.

When the module is in the GAP Central role it supports BLE device discovery,

connection initiation, and reading/writing data. Users can use different AT commands

to read/write data on BLE peripherals or receive updates from BLE peripherals via

UART.

The SPP with GAP Central application enables the SPP and BLE connections. If the

module is in the slave role it is ready to accept an SPP connection at any moment. If

the user application only requires GAP Central roles, then set the SPP role as Master

and ACON as OFF. This means that module will only connect to a remote SPP device

when the connection is initiated by the LM074 module with an AT command.

If the user application requires a SPP connection with ACON ON and BLE connections

it’s possible that the LM074 might connect with a remote SPP master device while

reading/writing data on the BLE Peripheral, or while performing some other task.

This will be indicated to user with

“IND*:CONNECTED=001122334455”. If so the user should use the escape sequence

i.e. +++ to come out of SPP-Online-Connected mode and then issue the required AT

commands.