User's Manual

Smart Machine Smart Decision
SIM868_Hardware_Design_V1.00 32 2016-06-20
The behavior of the RI pin is shown in the following figure when the module is used as a receiver.
HIGH
LOW
Idle Ring
Hang up the call
Establish the call
RI
Figure 25: UART1_RI behaviour of voice calling as a receiver
HIGH
LOW
Idle
RI
120ms
Receive SMS
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
LOW
Idle
Ring
Establish
the call
Hang up
the call
Idle
RI
Figure 27: UART1_RI behaviour as a caller
4.7. Audio Interfaces
SIM868 provides an analog input (MICP; MICN), which could be used for electret microphone. The module also
provides two analog outputs (SPK1P/2P; SPK1N/2N).
Table 13: Audio interface definition
SPK1P/1N output can directly drive 32Ω receiver.
Pin name Pin number Function
MICP 9 Audio input positive
MICN 10 Audio input negative
SPK1P 11 Audio output positive
SPK1N 12 Audio output negative
SPK2P 44 Audio output positive
SPK2N 43 Audio output negative