Pwm; Table 29: Adc Specification - SimCom SIM808 Hardware Design

"AT+CADC" to read the voltage value. For details of this AT command, please refer to document [1].

Table 29: ADC specification

Parameter
Voltage range
ADC Resolution
Sampling rate
ADC precision
Note: the voltage should less than 2.8V, or the ADC may be damaged.

4.15 PWM

Table 30: Pin definition of the PWM
Pin name
PWM1
PWM2
Note: SIM808 can only support 1 PWM synchronously, if customer set PIN 42 as PWM, so PIN41 can only be used as GPIO.
PWM output frequency varies from 0 to 2KHz.Two 7-bit unsigned binary parameters are used for the output
period and for the duty cycle. The AT command "AT + SPWM" is used to set the output period and duty cycle of
the PWM. For details, please refer to document [1].
A typical circuit of the PWM drives buzzer is shown in the following figure:
Table 31: Buzzer output characteristics
Parameter Min
Working voltage 2.5
Working current
Note: PWM pin must keep low when module in the boot process.
Table 32: PWM multiplex function
SIM808_Hardware Design_V1.00
Min Typ
0 -
- 10
- -
10
Pin number Description
42 PWM1, multiplex with GPIO4
41 PWM2, multiplex with GPIO3
4.7K
PWM
Figure 47: Reference circuit of PWM drive buzzer
Typ
2.8
Max
2.8
-
1.0833
20
VBAT
47K
Max Unit
2.9 V
16 mA
49
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Unit
V
bits
MHz
mV
2014.03.27