rhydoLABZ’s GSM/GPRS/GPS UART Modem is built with Quad Band GSM/GPRS/GPS engine SIM808, works on frequencies 850/900/1800/1900MHz and combines GPS technology for satellite navigation.This module is controlled by AT command via UART and supports 3.3V and 5V logical levels. The baud rate is configurable from 1200-115200 through AT command. The GSM/GPRS/GPS Modem is having internal TCP/IP stack to enable you to connect with internet via GPRS. It is suitable for SMS, Voice as well as DATA transfer application in M2M interface.

             The Modem is manufactured with Automatic Pick and place machine with high quality standard.The on board Low dropout 3A Power supply allows you to connect wide range unregulated power supply (5V-12V)  . Using this modem,you can make audio calls, SMS, Read SMS, attend the incoming calls,internet, GPS, Bluetooth   etc through simple AT commands.It provide ultra-low power consumption in sleep mode and integrated with charging circuit for Li-Ion batteries, that make it get a super long standby time and convenient for projects .

The Modem is coming with selectable interfacing voltage,which allows you to connect 2V8 to 5V .This modem can operate at both TTL 3.3V and 5V Logic Level  hence making it suitable for controllers at 5V logic level (PIC, AVR) as well as for 3.3V controllers like ARM based controllers and while interfacing depending upon the controller’s logic level .We should give appropriate voltage to the V_interface pin of the modem like 3.3V or 5V  and power the modem with supply range(4.5V-12V). Li-ion Battery is the power supply for the module, input voltage is from 3.4V to 4.4V. It uses the XH-2.0mm connector, that make it convenient to connect to 3.7V Li-Ion battery.


  •     Quad-band 850/900/1800/1900MHz.
  •     Controlled by AT Commands.
  •     Supports charging control for Li-Ion battery.
  •     Supports Real Time Clock.
  •     Supply voltage range 3.4V ~ 4.4V.
  •     Low power consumption, 1mA in sleep mode.
  •     Supports GPS NMEA protocol.
  •     Supports TCP/IP  and HTTP protocol.
  •     Standard SIM Card.
  •     normal operation temperature :-40°C~ +85°C.
  •     Built in Network Status LED.
  •     Inbuilt Powerful TCP/IP protocol stack for internet data transfer over GPRS.
  •     Input Voltage: 4.5V-12V DC.
  •     Audio interface Connector.
  •     On board SMA connector with GSM Antenna and GPS antenna.
  •     Provision for firmware updation.




K5-8 PIN






  • Insert an unlocked SIM card to SIM card Holder. 6 Pin Holder for SIM Cards is provided on the Modem.

  • Close SIM card Holder.Both 1.8 volts and 3.0 volts SIM Cards are supported by SIM808 – the SIM card voltage type is automatically detected.

  • Assemble GSM Antenna to the modem.
  • Connect serial cable to the modem.
  • Give power supply in between  4.5V to 12V through the power header OR using LIPO battery(3.7V) to Power up the module .
  • Default factory Baud rate is 9600.
  • When the modem is successfully powered-up, the Red LED on the modem (PWR) will be ON, the STS LED(GREEN) will light after 1-2 seconds and the NET LED(BLUE) will blink every second. After the Modem registers in the network (takes between 10-60 seconds), this LED will blink in step of 3 seconds.

The Network LED indicates the various status of GSM module eg. Power on, Network registration & GPRS connectivity. When the modem is powered up, this NETWORK LED will blink every second. After the Modem registers in the network (takes between 10-60 seconds), this LED will blink in step of 3 seconds. At this stage you can start using Modem for your application,showing that modem is registered with the network.


Check your GSM/GPRS  Modem Using  HYPERTERMINAL  in PC:

  • you need RS232 – TTL (5V) Converter or you can use FTDI Basic Breakout – 5V for making a connection between  SIM808 GSM/GPRS/GPS UART Modem and PC.
  • Before making connection with the system you should give external supply to the modem (4.5V-12V DC) or using LIPO battery(3.7V)  and make the ground of this supply common with GND of modem and the converter.
  • Firstly install a virtual serial port loading on the computer FT232RL drivers. Once the drivers are installed, connect the modem, with USB/mini-USB cable, and wait while it is found and that mean drivers are actually installed.
  • The connection details and interfacing requirements of  with SIM808 GSM/GPRS/GPS UART Modem and rhydoLABZ FTDI Basic Breakout-5V is as shown below

  • Connections should be like below :
    1. TX(modem)-RX(converter TTL)
    2. RX(modem)-TX(converter TTL)
    3. V-INT(modem)-pwr(converter TTL)
    4. Make ground (GND-GND)common.
  • Many embedded devices communicate over the serial port connection as most modern computers lack a hardware serial port;USB adaptors are used to convert USB data to standard serial port data and vice versa.
  • Once you are done with all these procedures, choose the appropriate COM port that got assigned to the USB in your system by looking into the device manager like as shown below.

  • select the serial software Hyper terminal and enter the name and press OK button .

Select the appropriate COM port(Check it on device manager). Set the baudrate  which should be 9600, parity none ,data bits 8 and stop bit 1 and flow control can also be kept as none.

 Now let’s try to check our Modem with AT commands for that we need to send following AT commands to Modem as shown  below

The above shown command :

  1. AT command (followed by enter) after “OK” response, this signifies that our Modem is working properly.
  2. ATE0 command (followed by enter) is being sent to stop the echo.
  3. AT+CREG? (followed by enter) is being used to check whether the SIM got registered or not

Sending a text message from PC using AT Commands and terminal

Now next let’s send a message using SIM808 GSM/GPRS/GPS UART Modem. For sending message we need to first send related AT commands to initialize the modem to send a message.

  • The AT+CMGF=1 command (followed by enter) sets the GSM Modem in SMS text mode.
  • AT+CMGS=<number>followed by enter gives<CR><write message><Ctrl+z>
    <CR> represents the carriage return character.
    <Ctrl+z>When you finish entering the SMS message body, you have to enter the <Ctrl+z> character to mark the end of the SMS message body.
    +CMGS: x and OK; where x = “current number of sent SMS messages”

Receiving a text message in Modem and displaying in terminal

 Now let’s receive a message using GSM/GPRS/GPS UART Modem .For receiving message we need to first send related AT commands to initialize the modem.

  • AT+CNMI=2,1,0,0,0 command (followed by enter) set the modem to indicate received messages with +CMTI response indicates that new message has been received and shows location number of last received message  in above figure it is shown by number ’19′.
  • AT+CMGR=<index> :<index>integer type; value in the range of location numbers supported by the associated memory and gives +CMGR response which includes status i.e “REC UNREAD” Received unread messages, Sender’s number,date, time and received message.

Receiving a voice call from Modem using AT Commands

  • For receiving call we need headset,connector jack and modem.
  • Headset is connected in the marked pins of GSM Modem.
  • Connections are given below
      1. Connect MIC -P of Modem to MIC-P of Jack.
      2. Connect MIC -N of Modem to MIC-N of Jack.
      3. Connect SPK-P of  Modem to SPK-P of Jack.
      4. Connect SPK-N of Modem to SPK-N of Jack.

    For receiving a call  firstly we need to send some AT commands as shown below.

  • Loudspeaker Volume Level

    – the value of max can be read by issuing the Test command
    For example:
      Command is used to select the volume of the internal loudspeaker audio
  • RING indicates incoming call.
  • For Attending call we are using ATA command (followed by enter) gives “OK” response when call is connected.
  • For Disconnecting call we are using ATH command  (followed by enter) gives “OK” response when call is disconnected.

Receiving GPS location from Modem using AT Commands

  • For GPS power control (ON/OFF)we are using AT+CGPSPWR=1 command (followed by enter) gives “OK” response when GPS is ON.
  • AT+CGPSSTATUS is used to Read the GPS fix status . AT+CGPSSTATUS? command(followed by enter) gives” +CGPSSTATUS: Location 3D Fix” response when GPS has fixed with 3D status
  •  AT+ CGPSOUT is used to Read GPS information. AT+ CGPSOUT=255 command (followed by enter)gives GPS NMEA data output .255 will allow all NMEA data output from Debug UART.
Test with PIC16F877A
  • Sample code shows how we can send a message using PIC interfacing  with modem.

Test  with Arduino
  • Sample code shows how we can send a message using arduino interfacing  with modem.


How to Buy


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