In base configuration the system comprises of at least two parts: main (MCU) and transport modules. Main module is driven by ATMega1280 chip with four hardware serial ports, dedicated I2C realtime clock and thermometer/thermostat, primary and backup stabilized power supplies, microSD card, parallel interface for 2 lines x 16 chars alphabetical LCD display, speaker output, four independent digital inputs for sensors, one input line for tamper detection, two 10A 240 VAC relay outputs, JTAG and ISP interfaces for programming/debugging and numerous extension connectors. The module also has USB-to-Serial interface allowing to reprogram, reconfigure and debug the system by connecting it to a desktop PC/notebook via USB port.
Interaction with the outer world is achieved by using unified interchangeable transport modules to make the system independent from any communication interface. For example, if the system is to be deployed at a remote location then the most appropriate way of communication would be GSM network accessed through GPRS modem. Potentially, transport module could provide just about any interface, for example, Ethernet, Zigbee, Bluetooth or something else. In this instructable we will be using GSM transport module.
In this particular application the project used as a security system with a picture triggered by PIR sensor and immediate uploading to a remote storage. The system could be set to active/inactive mode by either a RC from broken TV/DVD or by sending SMS. Apart from sensors picture may also be requested by sending SMS.