SIM900 GSM/GPRS Shield (for Arduino)

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Pins Definition

Interface Pin Description
GPIOs 1 VDD *
GPIOs 2 GND
GPIOs 3 GPIO1
GPIOs 4 GPIO2
GPIOs 5 GPIO3
GPIOs 6 GPIO4
GPIOs 7 GPIO5
GPIOs 8 GPIO6
GPIOs 9 GPIO7
GPIOs 10 GPIO8
GPIOs 11 GPIO9
GPIOs 12 GPIO10
GPIOs 13 GPIO11
GPIOs 14 GPIO12
GPIOs 15 GND
GPIOs 16 VDD*
UART 1 GND
UART 2 DTR
UART 3 RI
UART 4 DCD
UART 5 CTS
UART 6 RTS
UART 7 TXD
UART 8 RXD
IIC&PWM 1 GND
IIC&PWM 2 GND
IIC&PWM 3 IIC_SCL
IIC&PWM 4 IIC_SDA
IIC&PWM 5 PWM2
IIC&PWM 6 PWM1
IIC&PWM 7 GND
IIC&PWM 8 GND
Debug_Port 1 GND
Debug_Port 2 PERKEY
Debug_Port 3 DBG_RXD
Debug_Port 4 DBG_TXD

VDD* = 3.0V
Note 1: the operation level of the port is 3.0V

Installation

SIM900 Shield installation.png

Com Switch

There is a com switch for selecting the communicate port to UART port or Debug port of SIM900 module as the following figure 7. When connect to the SIM900 debug port, the UART multiplexer just can be set as Figure 4 or 5. Com witch arduino sim900.png

RI Behavior Output

There is a Jumper for configuration of RI, one to connect D3, another to connect D14.

Status RI response
Standby High
Voice call The pin is changed to low. When any of the following events occur, the pin will be changed to high:

(1) Establish the call
(2) Hang up the call

Data call The pin is changed to low. When any of the following events occur, the pin will be changed to high:

(3) Establish the call
(4) Hang up the call

SMS The pin is changed to low, and kept low for 120ms when a SMS is received. Then it is changed to high.
URC The pin is changed to low, and kept low for 120ms when some URCs are reported. Then it is changed to high.


The behavior of the RI pin is shown in the following figure when SIM900 module is used as a receiver.

Ri hebavior.png
When the module is used as caller, the RI will remain high.

Indicator LED and Buttons:

NETSTATUS: The status of the NETSTATUS LED is listed in following table:

Status Description
Off SIM900 is not running
64ms On/800ms Off SIM900 not registered the network
64ms On/3000ms Off SIM900 registered to the network
64ms On/300ms Off GPRS communication is established
  • STATUS: Power status of SIM900.
  • PWR: Power status of IComSat.


  • SIM900-POWER: After the IComSat power on, you need to press the SIM900-POWER button for a
  • moment to power on the SIM900 module.
  • Sim900-RST: Reset the SIM900
  • Arduino-RST: Reset the Arduino.