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

Table 15: Status of the NETLIGHT pin
Status
Off
64ms On/ 800ms Off
64ms On/ 3000ms Off
64ms On/ 300ms Off
A reference circuit is recommended in the following figure:

4.13 General Purpose Input/Output (GPIO)

SIM900D provides 2 GPIO pins. The output voltage level of the GPIO can be set by the AT command "AT+
SGPIO". The input voltage level of the GPIO can also be read by the AT command "AT+ SGPIO". For more
details, please refer to document [1].
Table 16: Pin definition of the GPIO interface
Pin name Pin number
GPO1 40
KBR0 10

4.14 PWM

SIM900D provides one PWM which can be used to control 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 ring
tones or alert tones. The tone level can be adjusted over a 24 dB range in 4 dB steps, or it can be muted
For details, please refer to document[1]
SIM900D_Hardware Design_V2.02
SIM900D behavior
SIM900D is not running
SIM900D not registered the network
SIM900D registered to the network
GPRS communication is established
Figure 36: Reference circuit of NETLIGHT
Default function
GPIO1
GPIO2
39
Smart Machine Smart Decision
Second function Default state
Output, pull down
SIM card detection Output, pull down
2012-05-07