General Purpose Input Output (Gpio); Pwm - SimCom SIM900D Hardware Design

SIM900D Hardware Design

3.16 General Purpose Input Output (GPIO)

SIM900D provides a limited number of General Purpose Input/Output signal pin. The output and input voltage
level of the GPIO can be set by AT command. For more details, please refer to related document [1]
Table23: Pin definition of the GPIO interface
Pin Name Pin Number
KBR0 10
GPO1 40
The SIM card detection function can be implemented, please refer to 3.11 SIM interface for more details.

3.17 PWM

SIM900D contains one Pulse-Width Modulators (PWM) which can be used for controlling a buzzer.
Features of buzzer PWM:
10-bit resolution for buzzer tone frequency generation from 200 Hz to 5 kHz
Tone frequency error < 1 % for all standard piano notes from 200 Hz to 5 kHz
Tone level control from 0 dB down to −24 dB in +4 dB steps
Audio mute
The PWM for the buzzer outputs a square wave at the desired tone frequency. The tone frequencies are
programmable from 200 Hz to 5 kHz and can be re-programmed on-the-fly to generate monophonic audio
SIM900D_Hardware Design_V1.04
MODULE
NETLIGHT
Figure33: Reference circuit of NETLIGHT
Default Function
GPIO8
GPIO1
51
VBAT
300R
4.7K
47K
Second Function
SIM card detection
Default State
Output Pull down
Output Pull down
2010.10.09