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
Table 20: Pin define of the GPIO interface
Pin Name Pin Number Default
Function
Second Function* Default State
GPIO1/ KBR4
40 GPIO1
KBR4
Pull down
GPIO2/ KBR3
41 GPIO2
KBR3
Pull down
GPIO3/ KBR2
42 GPIO3
KBR2
Pull down
GPIO4/ KBR1
43 GPIO4
KBR1
Pull down
GPIO5/ KBR0
44 GPIO5
KBR0
Pull down
GPIO6/ KBC4
47 GPIO6
KBC4
Pull down
GPIO7/ KBC3
48 GPIO7
KBC3
Pull down
GPIO8/ KBC2
49 GPIO8
KBC2
Pull down
GPIO9/ KBC1
50 GPIO9
KBC1
Pull down
GPIO10/ KBC0
51 GPIO10
KBC0
Pull down
GPIO11 67 GPIO11 Pull down
GPIO12 68 GPIO12 Pull down
*Note: This function is not supported in the default firmware. There must be customized firmware if you want.
Please contact SIMCom for more details.
3.17 External Reset
The external NRESET pin provides a means for external circuitry to force the device into a reset state. This
signal has to be considered as an emergency reset only. Asserting an active-low signal on the NRESET pin
generates a reset; already pull up in module. A decoupling of the NRESET pin may be necessary to avoid
erroneous noise-induced resets.
Figure 35: Reset timing
SIM900_HD_V1.01 26.12.2009
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