SIM900A GPRS Module TC35
I VBTA, GND of power supply (VBTA must be 3.5-4.5V 1A above ), VBTA a pin three by one on the line . But the power of your microcontroller MCU GND and the ground should be connected , then the map arbitrary GND on the line .
Cross Connection II Note : RXD0 pick 3.3V MCU TXD pin , TXD0 pick 3.3V microcontroller RXD pin , computer debug module (usb turn TTL, 232 rpm TTL) , it is also a cross- wiring. Not very familiar with serial communication students pay attention ! ( Used with a serial microcontroller development board to know when the debug module : computers and microcontrollers is a cross- wiring, so MCU control and the use of computer control module wiring sequence is not the same ) .
III S_POWER_KEY can VBTA short , you can also use single-chip high-level control .
Not shown on the schematic several other pin is of no use , and imitation is fixed firmly to plug opposite. The module does not lead voice interface , you can call, but not interactive voice . The main application of the vast majority of projects are texting and GPRS function, voice calls do not have much practical significance.
5 , LED: power indicator, signal indicator module , serial communication instructions
6 , clamshell SIM card connector with EMI immunity circuitry.
7 , the core plate with mounting holes , and auxiliary fixed pin , can be embedded directly into your production were to go , convenient, stable and fast.
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