RPI a-gsm shield serial and modem control description
can be seen in picture up-there
POWER using via a-gsm Vin PIN for serial connection
You can use any good quality external power adapter providing a voltage between 5.125V and 38V and supporting a current bigger than 1 A. Connect spare GND PIN located on 'Arduino power in connector' on a-gsm shield with the GND pin on your external power adapter. Connect the Vin PIN located on 'Arduino power in connector' on a-gsm shield with the Vout pin on your external power adapter. The a-gsm's POWER supply input selector must be in 'use Vin' position.
![Gsm Gsm](https://images-na.ssl-images-amazon.com/images/I/71mgDoT28CL._SX522_.jpg)
Power via USB variant for serial connection
Power the a-gsm board over USB, using a good quality power adaptor (eg. your Arduino/iPhone power adapter). The a-gsm's POWER supply input selector must be in 'use USB' position.
Choose a GSM Modem. A GSM modem, 3G modem or SIM box is basically a GSM phone without keyboard, speaker, battery and display. The terms SIM box, GSM gateway or GSM router are mostly used for devices that route phone calls through the GSM network and the term GSM modem or 3G modem for devices specialized in wireless data transmission. SIM800 Quad Band GSM/GPRS Serial Modem,gsm modem sim800 gsm module,sim800,800,gsm800,gsm module. Li-Fi - Visible Light Communication. Li-Fi technology provides transmission of data through illumination by sending data through&nb.
Power using the RPI 5V PIN for serial connection
Connect PIN 02/04 on Raspberry PI B+ extension connector with 5V PIN on 'Arduino power in connector' on a-gsm shield. The a-gsm's POWER supply input selector must be in 'use 5V' position.
![Sim Sim](https://vignette.wikia.nocookie.net/elementzonline/images/5/5d/SIM800_sim.jpg/revision/latest?cb=20160324183918)
IMPORTANT!!! The RPI power supply adapter must be rated for a minimum 2A sustained load without decrease supplied voltage under 5.05-5.10 V, in order to cover powering need for both boards regardless application, location, time...