User's Manual

HiLo3G-850 User Manual
04 March 2011 - Page 15 / 36
Figure 14: Speaker performance requirements
3.3 PWM
One PWM pin is available on the HiLo3G-850. It‘s a general purpose PWM which can be used for driving a vibrating
device, keypad backlight or LED. The PWM pin can be controlled through AT commands, allowing several periods and
duty cycles. More details are given in the AT commands specifications document.
User application can set PWM output:
Frequency between: 0.125Hz and 8KHz
Duty range from: 0 to 100%
3.3.1 PWM for Buzzer connection
HiLo3G-850 module can manage PWM output to drive a buzzer. The buzzer can be used as an abnormal state alarm.
Resistors must be added to protect the buzzer. The value of these resistors depends on the buzzer and the transistor.
Normally, they can be set at 1KΩ.
Figure 15: Buzzer connection
3.3.2 Network LED
The HiLo3G-850 module can manage a network LED. The LED can be connected either to one of the available GPIO or to
the PWM.
The transistors can be found a in a single package referenced as UMDXX or PUMDXX Family.
Value of resistor R depends on characteristic of chosen LED; it is used to limit the current through the diode.
Use the AT command to set the GPIO or PWM used to control the LED.
Figure 16: Network LED connection