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Smart Machine Smart Decision
4.5.2
Software Upgrade and Debug
Refer to the following figure for debugging and upgrading software.
Figure 20: Connection for software upgrading and debugging
The serial port and the debug port support the CMOS level. If user connects the module to the computer, the
level shifter should be added between the DCE and DTE.
For details about software upgrading, please refer to
document [4]
.
4.6
Audio Interfaces
SIM900-DS provides two analog input interfaces, MIC1P/1N and MIC2P, which could be used for electret
microphone. The module also provides two analog output interfaces, SPK1P/1N and SPK2P,which 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]
and
document [5]
.
In order to improve audio performance, the following reference circuits are recommended. The audio signals have
to be layout according to differential signal layout rules as shown in following figures.
If user needs to use an
amplifier circuit for audio, National Semiconductor Company’s LM4890 is recommended.
4.6.1
Speaker Interface Configuration
SIM900-DS_Hardware Design_V1.00
26
2013-01-20
Figure 21: Speaker reference circuit
Содержание SIMCom SIM900-DS
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