Labels: circuit >> GSM/ EDGE Modem in PCI Interface >> Interface of mobile phone with micro-controller >> microcontroller >> schematic >> Supporting AT commands How To Interface a mobile Phone with micro-controller 8051 family like at89s51, at89s52, at89c2051 etc.The project is aimed at developing and testing the use of mobile phones to remotely control an appliance control system. The microcontroller would then control an device based on the information given to it. The proposed solution will need to be easy to use, simple, secure, robust and be useful on most mobile phones. To achieve this testing will need to be carried out to create a useful system. The report consists of a background into the area of 8051 microcontroller and mobile communication, how they are interfaced to each other and AT (Attention) commands set used in communication.
The simplist method to interface a mobile with microcontroller is use mobile phone which support AT Commands. By using this we can directly connect that phone via datacable to microcontroller kit at a baud rate of 9600 and you can send AT commands to that mobile to read and send sms or other data of interest. The first thing in this regard is to find a mobile phone with AT Commands. Recommendation is use sony erricson’s 290i . You can use any other mobile suitable for this purpose.
The same program with slight modifications for AVR microcontroller. Which avr microcontroller you want to use and what is the sensor you want to interface. After connecting a mobile phone or GSM/GPRS modem to a computer, you can control the mobile phone or GSM/GPRS modem by sending instructions to it. The instructions used for controlling the mobile phone or GSM/GPRS modem are called AT commands. (AT commands are also used to control dial-up modems for wired telephone system.) Dial-up modems, mobile phones and GSM/GPRS modems support a common set of standard AT commands. In addition to this common set of standard AT commands, mobile phones and GSM/GPRS modems support an extended set of AT commands. One use of the extended AT commands is to control the sending and receiving of SMS messages.
This device acts as interface between your microcontroller project and a GSM phone. It handles all modem data communication between the GSM phone and your micro-project. The best thing is that it decodes PDU into TEXT on the fly! It’s based on PIC16F877A microcontroller running on 16MHz at 5V. It has an onboard level converter for serial communication with the gsm phone because PIC’s UART RX input pin has a Schmitt trigger triggering at 4,5 – 5V while the phone is sending only approx. 3V from it’s TX pin. Control takes place by means of SMS (Short text Messages Service). When the mobile receives a predefined text message, like “alarm ON” or “Start pump”, the circuit automatically recognizes it as a command, and switches the output accordingly.
At the componets level this project of mobile interfacing with microcontroller can be divided into these parts:-
1. Two mobile phones, one for general use and will be handled remotely, the second is specific mobile which will be interfaced with microcontroller 8051.
2. Microcontroller with necessary components inculding power supply, crystal, RS-232 components etc.
3. Interfacinf board, This is interfacinf board which will inculde the optocouplers, relays and other components required for interfacing of different input and output devices to microcontroller.
4. The hardware devices which are to be controlled through this projects will be connected to microcontroller usig above mentioned interfaing board.
The procdure for the mobile controlling of different hardware is very easy.
process begins on writing a SMS on mobile # 1, which will be transmitted to mobile # 2 through mobile networks. The second mobile will get that SMS and will transmit it to microcontroller via serial communication RS-232. The micocontroller 8051 will check, if it is according to predefine commnad then, according action will be performed.