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4.5.3
Debug Interface
SIM800H could achieve software debug function through USB interface. When powering on the module,
connect VBUS,USB_DP,USB_DM, and GND to PC, then install the driver following the prompts, a UART port
could be recognized by PC, customer could achieve the software Debug with this UART port.
SIMcom recommendeds the following connected diagram:
Figure 24: USB reference circuit
The TVS on USB data line should be less than 5pf, and traced by differential forms.
Note: please reserve the USB interface or test point for the further debugging
Table 10: VBUS operation voltage
Pin
Min
Typ
Max
Unit
VBUS
4.3
5
7
V
4.5.4
Software Upgrade and Debug
Customer could upgrade module’s firmware through USB or UART interface.
If upgrading through USB port, it is necessary to power on SIM800H 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 SIM800H
detects VBUS and could communicate normally with USB_DP and USB_DM, it will enter USB download mode
automatically.
Note: When only USB_DP and USB_DM are connected, no VBUS, customer need to pull down COL0(pin20)
before power on the module, then press the PWRKEY button, the module will enter download mode;
If customer upgrades the software through UART port, 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.
SIM800H_Hardware_Design_V1.01
33
2013-08-20
