Smart Machine Smart Decision
SIM800C_Hardware_Design_V1.02 29 2015-4-27
HIGH
LO W
Id leRing
H ang up the call
Establish the call
RI
Figure 25: UART1_RI behaviour of voice calling as a receiver
HIGH
LO W
Id le
RI
120m s
Receive S M S
URC
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.
HIGH
LO W
Id le
Ring
Establish
th e c a ll
H ang up
th e c a ll
Id le
RI
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 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
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