SIM800H datasheet(33/73 Pages) SIMCOM

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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 SIM800H&SIM800L first, then connect VBUS,

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

SIM800H&SIM800L detects VBUS and could communicate normally with USB_DP and USB_DN, it will enter

USB download mode automatically.

Note: When only USB_DP and USB_DN are connected, no VBUS, customers need to pull down KBC0 (pin20) before power on

the module, then press the PWRKEY button, the module will enter download mode.

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.

Figure 26: 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.

SIM800H&SIM800L_Hardware Design_V2.02

2015-07-27

SIM800H Datasheet(PDF) 33 Page - SIMCom