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
z Li-battery backup
Coin-type Rechargeable Capacitor such as XH414H-IV01E form Seiko can be used.
Typical charge curves for each cell type are shown in following figures. Note that the rechargeable Lithium type
coin cells generally come pre-charged from the vendor.
Figure 19: Seiko XH414H-IV01E Charge Characteristic
3.8 Serial Interfaces
Table 7: Pin definition of the serial interfaces
Name Pin Function
DTR 3 Data terminal ready
RI 4 Ring indicator
DCD 5 Data carrier detection
DSR 6 Date set ready
CTS 7 Clear to send
RTS 8 Request to send
TXD 9 Transmit data
Serial port
RXD 10 Receive data
DBG_RXD 28 Receive data
Debug port
DBG_TXD 27 Transmit data
SIM900 provides two unbalanced asynchronous serial ports. One is the serial port and the other is the debug port.
SIM900_HD_V1.01 26.12.2009
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