Arduino: SIM900 and SIM900A

As mentioned in the previous posts, if you plan on using the Arduino boards from remote locations, the only way to connect them to the internet is by using GSM shields. The most commonly used GSM shield (or module) is of course the SIM900. Their price is way lower than any other and you can get them for as low as $12. The SIM900 is actually a GSM chip that is usually mounted on a circuit board on which it has its pins soldered out for jumper wire connection. This way you can easily connect any development board and use it out of the box.

There are 2 versions of the chip: SIM900 and SIM900A

sim900 sim900a

SIM900 operates on Quad-Band 850/ 900/ 1800/ 1900 MHz – which means that you can use it everywhere in the world. On the other hand the SIM900A operates on Dual-Band 900/ 1800 MHz and the manufacturer states it is designed exclusively for Chinese market. This actually does mean that it is not intended to be used in Europe or USA, but you can flash the chip with the SIM900 firmware which allows it to work just like the SIM900*

* NOTICE: Flashing the SIM900A chip does not make it work on all the frequencies, because it only supports 900 and 1800 MHz, it only unlocks it for use outside of China.

Here are the full specs of the chips:

SIM900

SIMCom presents an ultra compact and reliable wireless module-SIM900. This is a complete Quad-band GSM/GPRS module in a SMT type and designed with a very powerful single-chip processor integrating AMR926EJ-S core, allowing you to benefit from small dimensions and cost-effective solutions.
Featuring an industry-standard interface, the SIM900 delivers GSM/GPRS 850/900/1800/1900MHz performance for voice, SMS, Data, and Fax in a small form factor and with low power consumption. With a tiny configuration of 24mm x 24mm x 3 mm, SIM900 can fit almost all the space requirements in your M2M applications, especially for slim and compact demands of design.

General features:

Quad-Band 850/ 900/ 1800/ 1900 MHz
GPRS multi-slot class 10/8
GPRS mobile station class B
Compliant to GSM phase 2/2+
– Class 4 (2 W @850/ 900 MHz)
– 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)
SIM application toolkit
Supply voltage range : 3.1 … 4.8V
Low power consumption: 1.5mA(sleep mode)
Operation temperature: -40°C to +85 °C

Specifications for Fax:

Group 3, class 1

Specifications for Data:

GPRS class 10: max. 85.6 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( available at late July ,2010)
FOTA ( available at July ,2010)
MMS (available at July ,2010)
Embedded AT (available at Q3,2010)

Specifications for Voice:

Tricodec
– Half rate (HR)
– Full rate (FR)
– Enhanced Full rate (EFR)
Hands-free operation (Echo suppression)
AMR
– Half rate (HR)
– Full rate (FR)

Interfaces:

Interface to external SIM 3V/ 1.8V
analog audio interface
RTC backup
SPI interface (option)
Serial interface
Antenna pad
I2C
GPIO
PWM
ADC

Compatibility:

AT cellular command interface

Certificates:

CE
FCC
ROHS
PTCRB
GCF
IC
ICASA
TA
REACH
AT&T

SIM900A

SIMCom presents an ultra compact and reliable wireless module. The SIM900A is a complete Dual-band GSM/GPRS module in a SMT type which is designed specially for Chinese market, allowing you to benefit from small dimensions and cost-effective solutions.
Featuring an industry-standard interface, the SIM900A delivers GSM/GPRS 900/1800MHz performance for voice, SMS, Data, and Fax in a small form factor and with low power consumption. With a tiny configuration of 24mm x 24mm x 3 mm, SIM900A can fit almost all the space requirements in your applications, especially for slim and compact demand of design.

General features:

Dual-Band 900/ 1800 MHz
GPRS multi-slot class 10/8
GPRS mobile station class B
Compliant to GSM phase 2/2+
– Class 4 (2 W @900 MHz)
– Class 1 (1 W @ 1800MHz)
Dimensions: 24*24*3 mm
Weight: 3.4g
Control via AT commands (GSM 07.07 ,07.05 and
SIMCOM enhanced AT Commands)
SIM application toolkit
Supply voltage range : 3.1 … 4.8V
Low power consumption: 1.5mA(sleep mode)
Operation temperature: -40°C to +85 °C

Specifications for Fax:

Group 3, class 1

Specifications for Data:

GPRS class 10: max. 85.6 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( available at July ,2010)

Enhanced version add following features:

FOTA ( available at July ,2010)
MMS (available at July ,2010)
Embedded AT (available at Q3,2010)

Specifications for Voice:

Tricodec
– Half rate (HR)
– Full rate (FR)
– Enhanced Full rate (EFR)
Hands-free operation
(Echo suppression)
AMR
– Half rate (HR)
– Full rate (FR)

Interfaces:

Interface to external SIM 3V/ 1.8V
analog audio interface
RTC backup
SPI interface
Two Serial interfaces
Antenna pad
I2C
GPIO
PWM
ADC

Compatibility:

AT cellular command interface

Certificates:

ROHS
TA
REACH