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
Figure 31: Reference circuit of the keypad interface
*Note: This function is not supported in the default firmware. There must be customized firmware if you want.
Please contact SIMCom for more details.
3.13 ADC
SIM900 provides one auxiliary ADC (General purpose analog to digital converter.) as voltage input pin, which
can be used to detect the values of some external items such as voltage, temperature etc. We can use AT
command “AT+CADC” to read the voltage value on ADC. For detail of this AT command, please refer to
document [1].
Table
17: ADC specification
MIN Type MAX Units
Voltage range 0 - 3 V
ADC Resolution - 10 - bits
Sampling rate - - 200K Hz
SIM900_HD_V1.01 26.12.2009
43