Hardware Design V1.01(091226)
Table Of Contents
- Contents
- Version history
- 1 Introduction
- 2 SIM900 Overview
- 3 Application Interface
- 3.1 SIM900 Pin Description
- 3.2 Operating Modes
- 3.3 Power Supply
- 3.4 Power Up and Power Down Scenarios
- 3.5 Power Saving
- 3.6 Summary of State Transitions (except SLEEP mode)
- 3.7 RTC Backup
- 3.8 Serial Interfaces
- 3.9 Audio Interfaces
- 3.10 SIM Card Interface
- 3.11 LCD Display Interface
- 3.12 Keypad Interface
- 3.13 ADC
- 3.14 Behaviors of the RI
- 3.15 Network Status Indication
- 3.16 General Purpose Input Output (GPIO)
- 3.17 External Reset
- 3.18 PWM
- 3.19 I2C Bus
- 4 Antenna Interface
- 5 Electrical, Reliability and Radio Characteristics
- 6 Mechanics
SIM900 Hardware Design
add a switch between the PWRKEY and the GND. The PWRKEY should be connected to the GND when
SIM900 is upgrading software. Please refer to the following figures.
Figure 21: Connection of software upgrade and software debug
The serial port and the debug port don’t support the RS_232 level and it only supports the CMOS level. Please
refer to the table 10 for details about the voltage level. You should add the level converter IC between the DCE
and DTE, if you connect it to the computer. Please refer to the following figure.
Figure 22: RS232 level converter circuit
SIM900_HD_V1.01 26.12.2009
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