User's Guide

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LM074 SPP with GAP Central Application v1.1

4. LM074 AT commands and Default configuration

This section describes the AT command structure for the LM074 module.

Serial terminals (such as Hercules, HyperTerminal, Tera Term or Putty) can be

used for serial communication with the LM074.

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

AT command strings after receiving “CR-LF” sequence.

AT Commands are case insensitive e.g. “At*Resp=On”, “at*resp=on” and

“AT*RESP=ON” are all valid.

AT command types:

1. Query only commands - Commands to query Module state, firmware

version number etc.

2. Query and Set commands - Commands to query the setting and

modify Module setting e.g. discoverability, Role, Baud, etc.

3. Execution only command – commands to perform specific action e.g.

start discovery for Bluetooth devices, start connection procedure, start

upgrade procedure etc.

The LM074 outputs messages to the user through the serial port for indications

like connection/pairing request, result of connection/pair procedure, result of

Bluetooth devices discovery, disconnection indication etc.

After the indication message is displayed, the LM074 waits for inputs from the

user to execute further action. For example, after incoming pairing indications,

enter accept/reject pair response or after indication for PASSKEY_cfm, provide

yes/no confirmation for the passkey etc.

The module responds to each AT command as “OK”\r\n or “ERR”\r\n. After

this response the module takes requested action or it will output report to the

user on UART. If module does not receive “AT” as a start of new command,

the module may not respond to this command even if it is terminated with

“\r\n” (e.g. instead of “AT*NAME=?”, user issues “A*name=?”). Module will

neglect the received string and is ready to receive new AT command and to

process it.

When the module does not receive any command on UART for more than 30

seconds, the module enters deep sleep mode. The module can come out of

this mode on UART activity or BT activity. If the user enters AT commands

while the module is in deep sleep, the module may lose the first character of

an AT command, e.g. for command “AT*NAME=?”, module may show the echo

as “t*name=?” or “Ñname=?” i.e. some garbage character at start. The

module will not respond to AT commands such as ERR/OK, but it ignores this

data and waits for a new AT command to process.