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
3.11 LCD Display Interface
SIM900 provides a serial LCD display interface that supports serial communication with LCD device. When
used as LCD interface, the following table is the pin definition. LCD interface timing should be united with
the LCD device.
Table 15: Pin define of the LCD interface
Pin Name Pin Number Function
DISP_CLK 11 Display clock for LCD
DISP_DATA 12 Display data output
DISP_D/C 13 Display data or command select
DISP_CS 14 Display enable
Note: This function is not supported in the default firmware. There must be some customized firmware if you
want. Please contact SIMCom for more details.
3.12 Keypad Interface
The keypad interface consists of 5 keypad column outputs and 5 keypad row inputs. The basic configuration is 5
keypad columns and 5 keypad rows, giving 25 keys.
Table
16: Pin define of the keypad interface
Pin Name Pin Number Default
Function
Second Function* Default State
GPIO1/ KBR4 40 GPIO1 Pull down
GPIO2/ KBR3 41 GPIO2 Pull down
GPIO3/ KBR2 42 GPIO3 Pull down
GPIO4/ KBR1 43 GPIO4 Pull down
GPIO5/ KBR0 44 GPIO5
Keypad matrix column
Pull down
GPIO6/ KBC4 47 GPIO6 Pull down
GPIO7/ KBC3 48 GPIO7 Pull down
GPIO8/ KBC2 49 GPIO8 Pull down
GPIO9/ KBC1 50 GPIO9 Pull down
GPIO10/ KBC0 51 GPIO10
Keypad matrix row
Pull down
The keypad interface allows a direct external matrix connection. A typical recommended circuit about the keypad
is as shown in the following figure.
SIM900_HD_V1.01 26.12.2009
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