Rhydo SIM 900 SIM 900 -TTL UART Dokumentacja Pobierz pdf (Strona 10)

SIM900 Reference Design Guide Notes

Figure 6: Serial Port Connection

SIM900_AN_Reference Design Guide_V1.01 01.27.2010

DBG_TXD

DBG_RXD

GND

DBG_TXD

DBG_RXD

GND

TXD

RXD

GND

UART

Figure 7: Debug Port Connection

2.3 GPIO selection

2.3.1 STATUS and NETLIGHT

STATUS pin can be used to monitor the module state during the power on/off process. After

power up, AT command will response till the STATUS change high, and it will change low after

the module log off from the base station in a power down procedure. It can be connected to a

GPIO of the MCU.

NETLIGHT is a net status indicator. It can drive a transistor to control a LED which will blink

slowly or quickly according to different states. Please note that it can’t drive a LED directly.

Both STATUS and NETLIGHT is dedicated in SIM900, they can not be used as a GPIO for the

customer.

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Rhydo SIM 900 SIM 900 -TTL UART Dokumentacja Strona 10