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Pin functions

  • Pin RI: can indicate the incoming call with a TTL signal, this can also connect to a MCU port, it is connected to Net1 onboard LED too.
  • Board provide VCHG battery charge pin: as well as a temperature check pin for battery, when a lithium battery attach between pin VCHG and GND, it will be charged by a provided 4.2 volt.

SIM908 Dev. Board


Name Description
SW101 Power On/Off
GSM PORT Serial (AT command input,GPRS data input)
GPS PORT GPS debug test
LED D200 Power indication LED
LED D201 Working status indication LED
CN102 USB Port
J103 GSM Antenna Port
J100 GPS Antenna Port

Reference voltage test point

Reference voltage test point Voltage
Test Point 1 3.3V
Test Point 2 5.0V
Test Point 3 4.0V
Test Point 4 2.8V

SIM908 Mini Board

Status of On-board LEDs

Name Description
Net1 connect to pin RI, keep off when power on, will light on when there is an incoming call
Pwr Power status LED, keep constantly on
Net inform the network status, quick blink when network not yet registered or problematic, keep slowly blink when network registered.


  • Version 1.1: * Change main power LDO, may have better performance * Add extra power pins and Uart pins * Fit into a case design.
  • Version 1.2: Add extra logic leveled UART pins for arduino or Raspbery Pi such 5V or 3v3 devices


Pins definition 908.jpg

Video tutorial

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