Manual of Board ET-BASE GSM SIM900
6. Noteworthy Specifications of Signal
•
RI(Ring Indicator)
is Output from Module SIM900; normally, it
is High, but it becomes Active Low when there is an incoming
telephone call according to these conditions;
o
When there is any Voice Calling, Signal RI is Active LOW
and it still remains until it answers a calling (ATA) or
it receives a command to cancel a calling (ATH) or it
hangs up a telephone before answering.
o
When there is any Data calling, Signal RI is Active LOW
and it still remains until it answers a calling (ATA) or
it receives a command to cancel a calling (ATH).
o
When there is SMS, Signal RI is Active LOW for 120mS and
it becomes HIGH automatically.
•
DTR(Data Terminal Ready)
is Input of Module SIM900. The Module
runs when this Pin receives Logic LOW; but, it this Pin DTR
receives Logic HIGH, the Module stops running and enters Sleep
Mode automatically (if Enable Sleep Mode by Command
“AT+CSCLK=1”
). If user requires running the Module all the
time, it has to control Pin DTR on the Module side to receive
Logic LOW or it has to disable Sleep Mode by Command
“AT+CSCLK=0”
and then save this Configuration.
7. Example of using AT Command with Module SIM900
Module GSM/GPRS model SIM900 is designed and run as Modem, it
is used to connect, command, and communicate with Module through
RS232 Serial Port; it supports Baud Rate in the range of 1200-115200
bps and it uses AT Command. Its functions are similar to general
Modem but it adds Option and other special commands, so it is
suitable and compatible with capability of Module.
Please read further details of format and function of AT
Command in order to connect and command Module SIM900 from the
manual of AT Command (file document
SIM900_AT Command
Manual_V1.06.pdf
) in CD-ROM. In this case, it only describes format
and how to use commands briefly to be guideline for beginner to
study and understand the command. The format of AT Command begins
with ASCII Code of 2 characters that are “A” and “T”; in this case,
it can be either capital letter or small letter because the meaning
is the same. Next, it follows by Command Code and Option of command
(if yes). Remember, every command always ends by Enter or 0DH(13);
for example, the format of Command RESET is either “ATZ” or “atz”.
The command format is divided into 4 groups as follows;
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