Table Of Contents; Contents - SimCom SIM900B Hardware Design

Contents.................................................................................................................................................................... 3
Version History ........................................................................................................................................................ 7
1 Introduction....................................................................................................................................................... 8
2 SIM900B Overview........................................................................................................................................... 8
2.1 SIM900B Key Features ............................................................................................................................ 8
2.2 Operating Modes .................................................................................................................................... 10
2.3 SIM900B Functional Diagram ................................................................................................................11
3 Application Interface...................................................................................................................................... 12
3.1 Pin Description ....................................................................................................................................... 12
3.2 Power Supply.......................................................................................................................................... 14
3.2.1 Minimizing Voltage Drop of VBAT ................................................................................................... 15
3.2.2 Monitoring Power Supply ................................................................................................................... 15
3.3 Power on/down Scenarios ...................................................................................................................... 15
3.3.1 Power on SIM900B............................................................................................................................. 15
3.3.1.1 Turn on SIM900B Using the PWRKEY Pin (Power on) ..................................................................... 15
3.3.2 Power down SIM900B........................................................................................................................ 16
3.3.2.1 Power down SIM900B by the PWRKEY Pin ...................................................................................... 17
3.3.2.2 Power down of SIM900B by AT Command........................................................................................ 17
3.3.2.3 Over-voltage or Under-voltage Power down ....................................................................................... 17
3.3.2.4 Over-temperature or Under-temperature Power down ......................................................................... 18
3.3.3 Restart SIM900B by PWRKEY Pin.................................................................................................... 18
3.4 Power Saving Mode................................................................................................................................ 19
3.4.1 Minimum Functionality Mode ............................................................................................................ 19
3.4.2 Sleep Mode 1 (AT+CSCLK=1) .......................................................................................................... 19
3.4.3 Wake Up SIM900B from Sleep Mode 1 (AT+CSCLK=1)................................................................. 19
3.4.4 Sleep Mode 2 (AT+CSCLK=2) .......................................................................................................... 20
3.4.5 Wake Up SIM900B from Sleep Mode 2 (AT+CSCLK=2)................................................................. 20
3.5 RTC Backup ........................................................................................................................................... 20
3.6 Serial Interfaces ...................................................................................................................................... 21
3.6.1 Function of Serial Port and Debug Port .............................................................................................. 22
3.6.2 Software Upgrade and Debug ............................................................................................................. 23
3.7 Audio Interfaces ..................................................................................................................................... 23
3.7.1 Speaker Interface Configuration ......................................................................................................... 24
3.7.2 Microphone Interfaces Configuration ................................................................................................. 25
3.7.3 Earphone Interface Configuration....................................................................................................... 25
3.7.4 Audio Electronic Characteristics......................................................................................................... 25
3.8 SIM Card Interface ................................................................................................................................. 26
3.8.1 SIM Card Application ......................................................................................................................... 26
3.8.2 Design Considerations for SIM Card Holder ...................................................................................... 27
3.9 LCD Display/SPI Interface..................................................................................................................... 29
3.10 ADC........................................................................................................................................................ 30
3.11 RI Behaviors........................................................................................................................................... 30
SIM900B_Hardware Design_V2.01

Contents

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Smart Machine Smart Decision
2012-05-07