SIM800C datasheet(28/52 Pages) SIMCOM

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SIM800C_Hardware_Design_V1.02

2015-4-27

Min

Typ

Max

Unit

USB_VBUS

4.3

5.0

7.0

4.5.4

Software Upgrade

Customer could upgrade module’s firmware through USB or UART interface.

If upgrading through USB interface, it is necessary to power on SIM800C first, and then connect USB_VBUS,

USB_DP, USB_DN, and GND to PC. There is no need to operate PWRKEY pin in the whole procedure, when

SIM800C detects USB_VBUS and could communicate normally with USB_DP and USB_DN, it will enter USB

download mode automatically.

If customer upgrades the software through UART interface, it is strongly recommended to lead the UART1_TXD,

UART1_RXD, GND and PWRKEY pin to IO connector for the upgrading, and PWRKEY pin should connect to

GND while upgrading. Refer to the following figure for debugging and upgrading software.

UA R T 1_T X D

M odule(D C E )

UA R T 1_RX D

GN D

PW R K E Y

TX D

RX D

GN D

SerialP ort

PW R K E Y

I/O C onnector

Figure 24: Connection for software upgrading and debugging

The UART interface supports the CMOS level. If customer connects the module to the computer, the level shifter

should be added between the DCE and DTE.

4.6. UART1_RI Behaviors

Table 11: 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

SMS

The pin is changed to low, and kept low for 120ms when a SMS is received. Then it is changed

to high.

Others

For more details, please refer to document [2].

The behavior of the RI pin is shown in the following figure when the module is used as a receiver.

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