Rhydo SIM 900 -RS232 User manual

www.rhydolabz.com SIM900 GSM/GPRS RS232 Modem - User Manual
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Document : D a t a s h ee t Model # : G S M – 1934
Date : 10 - DEC -2011
SIM 900
SIM 900 SIM 900
SIM 900 –
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RS232RS232
RS232
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User Manua l
Rhydo Technologies (P) Ltd.
(An ISO 9001:2008 Certified R&D Company)
Golden Plaza, Chitoor Road,
Cochin – 82018, Kerala State, India
Phone : [phone], 2371
Cell : 0091- 994 70444
Fa : 0091 - 484-2370579
E-mail : [e-mail], [e-mail]
WebSite : http://www.rhydolabz.com

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GSM/GPRS RS232 Modem from rhydoLABZ is built with SIM COM Make SIM900 Quad-band
GSM/GPRS engine, works on frequencies 850 MHz, 900 MHz, 1800 MHz and 1900 MHz. It is very
compact in size and easy to use as plug in GSM Modem. The Modem is designed with RS232 Level
converter circuitry, which allows you to directly interface PC Serial port .The baud rate can be configurable
from 9 00-115200 through AT command. Initially Modem is in Autobaud mode. This GSM/GPRS RS232
Modem is having internal TCP/IP stack to enable you to connect with internet via GPRS. It is suitable for
SMS as well as DATA transfer application in M2M interface.
The modem needed only 3 wires (Tx,Rx,GND) except Power supply to interface with
microcontroller/Host PC. The built in Low Dropout Linear voltage regulator allows you to connect wide
range of unregulated power supply (4.2V -13V). Yes, 5 V is in between !! .Using this modem, you will be able
to send & Read SMS, connect to internet via GPRS through simple AT commands.
FEATURES
 High Quality Product (Not hobby grade)
 Quad-Band GSM/GPRS
850/ 900/ 1800/ 1900 MHz
 Built in RS232 Level Converter
(MAX3232)
 Configurable baud rate
 SMA connector with GSM L Type
Antenna.
 Built in SIM Card holder.
 Built in Network Status LED
 Inbuilt Powerful TCP/IP protocol stack
for internet data transfer over GPRS.
 Audio interface Connector
 Most Status & Controlling Pins are
available at Connector
 Normal operation temperature: -20 °C to
+55 °C
 Input Voltage: 5V-12V DC
SPECIFICATIONS
 Quad-Band 850/ 900/ 1800/ 1900 MHz
 GPRS multi-slot class 10/8
 GPRS mobile station class B
 Compliant to GSM phase 2/2+
o Class 4 (2 W @850/ 900 MHz)
o Class 1 (1 W @ 1800/1900MHz)
 Dimensions: 24*24*3mm
 Weight: 3.4g
 Control via AT commands (GSM 07.07
,07.05 and SIMCOM enhanced AT Commands)
 Low power consumption: 1.0mA(sleep
mode)
 Operation temperature: -40°C to +85 °C\
Specifications for Fa
 Group 3, class 1
Specifications for Data
 GPRS class 10: max. 85. kbps (downlink)
 PBCCH support
 Coding schemes CS 1, 2, 3, 4
 CSD up to 14.4 kbps
 USSD
 Non transparent mode
 PPP-stack
Specifications for SMS via GSM/GPRS
 Point to point MO and MT
 SMS cell broadcast
 Text and PDU mode
Software features
 0710 MUX protocol
 embedded TCP/UDP protocol
 FTP/HTTP
Special firmware
 MMS
 Java (cooperate with Iasolution)
 Embedded AT

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Specifications for Voice
 Tricodec
o Half rate (HR)
o Full rate (FR)
o Enhanced Full rate (EFR)
 Hands-free operation
 (Echo suppression)
 AMR
o Half rate (HR)
o Full rate (FR)
Interfaces
 Analog audio interface pins at 2mm Pitch
RMC
 RS232 Serial interface
 SMA Antenna Connector
 DC Power pins at 2mm Pitch RMC
Compatibility
 AT cellular command interface

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DIMENSIONS
OPERATING CONDITIONS
P
a
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e
t
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IN/OUT
Mi
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M
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Supply Voltage -
VIN
Input 4.2 13 V
Current
Consumption
--- 40 590 mA

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OPERATING MODES
The table below briefly summarizes the various operating modes referred to in the following chapters.
Mode Function
Normal
operation
GSM/GPRS
S EEP
Modem
will automatically go into S EEP m
ode if DTR is set to high level
and there is no on air and no hardware interrupt (such as data on serial
port). In this case, the current consumption of GSM Modem will reduce to
the minimal evel.
In S EEP mode, the Modem can still receive paging message and SMS from
the system normally.
GSM IDLE
Software is active.
Modem
has registe
red to the GSM networ , and the
modem is ready to send and receive.
GSM TALK
Connection between two subscribers is in pr
ogress. In this case, the
power consumption depends on networ settings such as DTX off/on,
FR/EFR/HR, hopping sequences, antenna.
GPRS
STANDBY
Modem
is ready for GPRS data transfer, b
ut no data is currently sent or
received. In this case, power consumption depends on networ settings
and GPRS configuration.
GPRS DATA
There is GPRS data transfer (PPP or TCP or
UDP) in progress. In this
case,power consumption is related with networ settings (e.g. power
controllevel), uplin / downlin data rates and GPRS configuration (e.g.
used multi-slot settings).
POWER
DOWN
Normal shutdown by sending the “AT+CPOWD=1” command or using the PWRKEY. The
power management ASIC disconnects the power supply from the baseband part of the
GSM Modem. Software is not active. The serial port is not accessible. Operating voltage
remains applied to the internal circuitry
Minimum
functionality
mode
(withoutremove
power
supply)
Use the “AT+CFUN” command can set the modem to a minimum functionality mode
without remove the power supply. In this case, the RF part of the modem will not wor
or the SIM card will not be accessible, or both RF part and SIM card will be closed, and
the serial port is still accessible. The power consumption in this case is very low.

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1.3 Turn Off GSM Modem Using AT Command
You can use the AT command “AT+CPOWD=1” to turn off the modem. This command lets the GSM Modem log off
from the network and allows the GSM Modem to enter into a secure state and save data before completely
disconnecting the power supply. Before the completion of the switching off procedure the GSM Modem will send
out result code:
“ NORMAL POWER DOWN”
After this moment, the AT commands can’t be executed. The GSM Modem enters the POWER DOWN mode, only
the RTC is still active. POWER DOWN can also be indicated by STATUS pin, which is a low level voltage in this
mode.
1.5 Power Saving
There are two methods for the GSM Modem to enter into low current consumption status. “AT+CFUN” is used to
set GSM Modem into minimum functionality mode and DTR hardware interface signal can be used to lead system
to be in S EEP mode (or slow clocking mode).
1.6 Minimum Functionality Mode
Minimum functionality mode reduces the functionality of the GSM Modem to a minimum and, thus, minimizes the
current consumption to the lowest level. This mode is set with the “AT+CFUN” command which provides the
choice of the functionality levels <fun>=0，1，4
• 0: minimum functionality;
• 1: full functionality (default);
• 4: disable phone both transmit and receive RF circuits;
If GSM MODEM has been set to minimum functionality by “AT+CFUN=0”, the RF function and SIM card function
will be closed. In this case, the serial port is still accessible, but all AT commands correlative with RF function or
SIM card function will not be accessible.
If GSM MODEM has been set by “AT+CFUN=4”, the RF function will be closed, the serial port is still active. In this
case all AT commands correlative with RF function will not be accessible.
After GSM MODEM has been set by “AT+CFUN=0” or “AT+CFUN=4”, it can return to full functionality by
“AT+CFUN=1”.
For detailed information about “AT+CFUN”, please refer to document [1].

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1.7 Sleep Mode (Slow Cloc Mode)
We can control SIM900 GSM Modem to enter or exit the S EEP mode in customer applications through DTR signal.
When DTR is in high level and there is no on air and hardware interrupt (such as GPIO interrupt or data on serial
port), GSM MODEM will enter S EEP mode automatically. In this mode, GSM MODEM can still receive paging or
SMS from network but the serial port is not accessible.
Note: For GSM MODEM, it requests to set AT command “AT+CSC K=1” to enable the sleep mode; the default
value is 0, that can’t make the GSM Modem enter sleep mode. For more details please refer to our AT command
list.
1.8 Wa e Up GSM MODEM from SLEEP Mode
When GSM MODEM is in S EEP mode, the following methods can wake up the GSM Modem.
• Enable DTR pin to wake up GSM MODEM.
If DTR pin is pulled down to a low level，this signal will wake up GSM MODEM from power saving mode.
The serial port will be active after DTR changed to low level for about 50ms.
• Receiving a voice or data call from network to wake up GSM MODEM.
• Receiving a SMS from network to wake up GSM MODEM.
1.9 Summary of State Transitions (except SLEEP mode)
The following figure shows how to proceed from one mode to another.
AT+CPOWD or Drive
PWRKEY to ground
Drive PWRKEY to ground
Normal Mode
PWR down
Mode

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2.0 Serial Interfaces
Name Pin Function
eriel Port DB9
GND
5
Ground
CTS
8
Clear to send
RTS
7
Request to send
TXD
2
Transmit data
RXD
3
Receive data
The GSM module is designed as a DCE (Data Communication Equipment), following the traditional DCE-DTE (Data
Terminal Equipment) connection. The GSM Modem and the client (DTE) are connected through the following
signal (as following figure shows). Auto bauding supports baud rate from 1200bps to 57600bps.
Serial port
• TXD: Send data to the RXD signal line of the DTE
• RXD: Receive data from the TXD signal line of the DTE
serial port of the GSM engine supports auto bauding for the following baud rates: 1200, 2400, 4800, 9600,
19200,38400 and 57600bps. Factory setting is auto bauding enabled. This gives you the flexibility to put the GSM
engine into operation no matter what baud rate your host application is configured to. To take advantage of auto
bauding mode, specific attention should be paid to the following requirements:
Synchronization between DTE and DCE:
When DCE powers on with the auto bauding enabled, user must first send “A” to synchronize the baud rate. It is
recommended to wait 2 to 3 seconds before sending “AT” character. After receiving the “OK” response, DTE and
DCE are correctly synchronized. The more information please refer to the AT command “AT+IPR”.

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Restrictions on autobauding operation
• The serial port has to be operated at 8 data bits, no parity and 1 stop bit (factory setting).
• The Unsolicited Result Codes like "RDY", "+CFUN: 1" and "+CPIN: READY” are not indicated when you start
up the ME while autobauding is enabled. This is due to the fact that the new baud rate is not detected
unless DTE and DCE are correctly synchronized as described above.
Note: You can use AT+IPR=x to set a fixed baud rate and save the configuration to non-volatile flash memory.
After the configuration is saved as fixed baud rate, the Unsolicited Result Codes like "RDY" should be received
from the serial port all the time that the GSM MODEM is power on.
AT Command Syntax
When DCE powers on with the autobauding enabled, user must first send “A” to synchronize the baud rate. It is
recommended to wait 2 to 3 seconds before sending “AT” character. After receiving the “OK” response, DTE and
DCE are correctly synchronized The “AT” or “at” prefix must be set at the beginning of each Command. To
terminate a Command line enter <CR> , otherwise known as carriage return or \r.
Commands are followed by a response that includes <CR>< F><response><CR>< F>. Only the responses are
presented in the document here, <CR>< F> are omitted intentionally.
Example: With ocal Echo enabled:
Transmit: AT\r
Receive: AT\r\r\nOK\r\n
SETTINGS FOR EASY MICROCONTROLLER COMMUNICATION
When communicating with the GSM Modem using a microcontroller, you usually want very short responses, no
local echo, and no startup messages.
Sticking on the &W to the end of the command saves the setting into memory.
ATV0&W\r Enable short response
ATE0&W\r Disable ocal Echo
AT+CIURC=0;&W\r Disable “CA READY” Startup Message
Now instead of commands returning OK or ERROR in plain text, as well as repeating all written commands, the
GSM Modem will not echo what you transmit and the GSM Modem will return error codes in single bytes. For
example, instead of:
Transmit: AT\r
Receive: \r\nOK\r\n

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You’ll have:
Transmit: AT\r
Receive: \r\n0\r\n
SAMPLE AT COMMANDS CODE
1. PHONE COMMUNICATION
Goal: Call a phone
Dial 123-456-7890 = ATD1234567890;\r
This command returns OK or ERROR. Returns NO CARRIER when phone hangs up
2. SEND A TEXT MESSAGE
Goal: Send a text
AT+CMGF=1\r
Returns OK or ERROR
AT+CSCS=”GSM”\r
Returns OK or ERROR
AT+CSCA=”[phone]” \r
Returns OK or ERROR. This number [phone] is the short
message center for AT&T/Cingular service. T-Mobile’s is [phone]
AT+CSMP=17,167,0,240\r
Returns OK or ERROR. These numbers refer to settings for text
message sending, keep them this way.
AT+CMGS=”
AT+CMGS=”1234567890”\r
Returns > , prompting what message to send. 1234567890 is the
phone number that the text message will be sent to.
Hello this is a message <Ctrl+z>