Smart Machine Smart Decision
SIM800C_Hardware_Design_V1.02
29
2015-4-27
H IG H
LO W
Idle
R ing
H ang up the call
E stablish the call
R I
Figure 25: UART1_RI behaviour of voice calling as a receiver
H IG H
LO W
Idle
R I
120m s
R eceive S M S
U R C
Figure 26: UART1_RI behaviour of URC or receive SMS
However, if the module is used as caller, the UART1_RI will remain high. Please refer to the following figure.
H IG H
LO W
Idle
R ing
E stablish
the call
H ang up
the call
Idle
R I
Figure 27: UART1_RI behaviour as a caller
4.7.
Audio Interfaces
SIM800C provides an analog input (MICP; MICN), which could be used for electret microphone. The module
also provides an analog output (SPKP; SPKN).
Table 12: Audio interface definition
SPKP/SPKN output can directly drive 32
Ω
receiver.
AT command “AT+CMIC” is used to adjust the input gain level of microphone. AT command “AT+SIDET”
is used to set the side-tone level. In addition, AT command “AT+CLVL” is used to adjust the output gain level.
For more details, please refer to
document [1].
Pin name
Pin number
Function
MICP
9
Audio input positive
MICN
10
Audio input negative
SPKP
11
Audio output positive
SPKN
12
Audio output negative
