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Obsolete (outdated should NOT use)


Board interface

  • D100  LED indicator 
  • CN101  6pin 2.54mm header interface 
  • J100  GPRS/GSM ANT 
  • J102  BT ANT(only for SIM800H) 
  • CN100  Micro SIM card socket 
  • C102  VRTC(Not mounted by default) 
  • TEST  2.8V 

Common Pin Definition

  • Power supply should provide sufficient current so that the  module  can  work  normally; the peak current is nearly 2A, will NOT work over 4.4V
name pin mark on pcb Description Comment
GND 1 and 6 G ground
Vbat 2 V Power range is from 3.4V to 4.4V.   Zenger diode is strongly recommended to anti surge on VBAT 
PWRkey 3 K Power down  Shorted with GND via R104 by default 
TXD 4 T Transmit Data TTL Series data Output 
RXD 5 R Receives Data  TTL Series data Input 

SIM800C-Full Board R1-old

SIM800C dev board dimension
  • Pin Definition
Pin Description Pin Description
GND Power ground VCC_IN power supply pin, input DC5V-20V, used to power the board
RI The kernel ringing pin DTR Data terminal preparation
TXD module serial send pin, TTL level (not directly connected to the RS232 level) RXD module serial receive pin, TTL level (not directly connected to the RS232 level)
U2_R module serial port 2 receive pin U2_T Module serial port 2 transmit pin
V_M This pin is used to convert the TXD and RXD of the GSM module board to the TTL logic of the corresponding target board. This is used to convert the TXD and RXD of the GSM module board to the corresponding TTL logic ADC ADC detection
SPP Core audio output pin SPN Core audio output pin
MC- Core audio input pin MC + Core audio input pin
PWR Pull down this pin to enable the module to be turned on or off BAT lithium battery input pin, 3.3v-4.4v


  • VBAT  MUST  be  lower  than  4.4V,  4.0V  is  recommended,  and  TXD/RXD are TTL level which can be directly connected with MCU.
  • Test pin, sim card voltage: Should confirm whether SIM card is inserted, and voltage test points should be 2.8V. 
  • Bluetooth must have enough current, USB power can not supply enough current


Supported countries for sim900A - > click to see on right side



Pin functions of SIM908

  • 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