Language OpenAT from the control unit microcontroller can be eliminated by making the "manage" the modem itself. The modem includes a microcontroller capable of performing custom applications. To write these applications there is free of charge to OpenAT, including a compiler, libraries, debugger and emulator. Wednesday OpenAT allows for more opportunities modem than using AT-commands. Libraries which are included in the environment, allow more flexible use of tcp / ip stack. When using OpenAT-applications, Wavecom modem into a completed device, handles the external signals and exchange data in a network gsm.
What to choose? Let us try to analyze the pros and cons of the above hardware solutions: The second solution is ideal if nominated by stringent requirements for size or to the cost of the device. In practice, however, a number of complexities that must be solved by a sophisticated algorithm of the device. When you create an autonomous unmanned devices is one of the most major problems – long-term resiliency. A simple example: how do you think, if the office of a company's system administrators will leave the network in the lurch, what is the probability that, say, three months the network will function properly? Non-performing gsm devices must operate reliably for years, guaranteed to restore the working capacity after any failure. It requires many painstaking research, but then pays off in work.
We give some examples of emergency situations arising in these devices: From time to time is "quiet" off the modem from the network gprs. In this case, the modem does not receive any messages about the network this fact. Accordingly, data packets are not sent. You may experience situations where sending packets for any reason it becomes impossible, and resumed only when you reboot your modem. Possible crashes SIM-card (only helps reset the modem). Possible loss of registration in the network gsm (for example, due to congestion), and after a long unsuccessful modem can stop trying to find the network. Can be blocked account because of the negative balance. Management application must provide a guaranteed restoration of efficiency devices after the disappearance of the contingency. Example implementation of an information collection system The project "Safe School" – is another example of constructing a system of increased reliability of data transmission based on GSM-making Wavecom. In this project needed to ensure continued readiness gprs channel for immediate transfer Notification Function. This problem was successfully solved by the developers of the firm "capacity." System reliability is ensured by special measures: In the present gsm system for collecting information based on the GSM-module Wismo Quick 2406 used simultaneously managing controller (AVR ATmega128) and Annex OpenAT. The device continuously monitors the state of GPRS-connection, and fulfills all there is an emergency situation. Communication device with the center carried out with simple communications protocol tcp / ip. In the information-gathering device for connecting arbitrary devices (radios, control panels, controllers, sensors, transducers directly) there are RS-232 and RS-485. Also, the device has two loops alarm for the possibility of connecting sensors penetrate into the room and open the enclosure. System reliability over time, develop the system was provided a large number of contingencies. Currently the system is in continuous operation. Devices are working flawlessly for over a year. In the strong acceleration of mobile network devices have shown high stability by delivering tcp / ip messages to the center, even when not pass deflected by sms and voice calls. A device for collecting information has a quality certificate.