SimCom SIM808, Проектирование аппаратного обеспечения

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4.6.4 Software Upgrade and Debug
Only USB and interface can be used for firmware upgrade.
If customer upgrading firmware via the USB port, SIM808 must be powered first, then connect VBUS, USB_DP,
USB_DM and GND to PC. There is no need to operate PWRKEY pin in the whole procedure, when SIM808
detects VBUS and could communicate normally by USB_DP and USB_DM, module will enter USB download
mode automatically.
Note: When only USB_DP and USB_DM connected, no VBUS, customer need to pull down COL0 before power on the module,
then press the PWRKEY button, the module will enter download mode;
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]
.
4.7 RI Behaviors
Table 13: RI Behaviors
State RI response
Standby High
Voice call
The pin is changed to low. When any of the following events occur, the pin will be
changed to high:
(1)Establish the call
(2)Hang up the call
Data call
The pin is changed to low. When any of the following events occur, the pin will be
changed to high:
(1)Establish the call
(2)Hang up the call
SMS
The pin is changed to low, and kept low for 120ms when a SMS is received. Then it is
changed to high.
URC
The pin is changed to low, and kept low for 120ms when some URCs are reported. Then it
is changed to high. For more details, please refer to
document [10].
The behavior of the RI pin is shown in the following figure when the module is used as a receiver.
Figure 28: RI behaviour of voice calling as a receiver
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