serial communication microcontroller and mobile phones

In communicating the cell phone / cell phone with the microcontroller to be used as a remote-controlled device required an interface that can synchronize the two devices so they can exchange data. Interface system in this study using phone data port communication lines embedded on the bottom of the phone to be able to communicate with a microcontroller series, the serial communication there are two main points that must be adjusted ie: stress levels and speed data rate (baud rate), after the second this is then adjusted so that both devices can communicate with these devices can be used as a remote-controlled device.

It was made by using micro controller as the main module, which will read incoming SMS to your mobile phone as an order issued by the control of the realization of micro-, and ordered the phone to send SMS reply to the mobile sender’s output status. In this script you can use almost any type of mobile phone data cable original specifications which are connected in series with the instrument, while the controller can be used for any phone with SMS facility.

Remote control technology has been developed by using various transmission media. Some of them are remote control using infrared media, radio, internet and phone lines. Remote control system via the telephone line has an advantage in terms of range and practicality compared with other media.
The presence of mobile phone (cellular) or mobile phones that have been known and used a lot of people that are able to communicate wherever they are without being limited by space and the span length of the cord could be a solution for the needs of remote control (remote control) as was described above.

One of the most popular cell phone function is to send and receive SMS. SMS is very suitable for real time control system for wireless data transfer speed, efficiency and breadth of coverage, but the excess mobile phone with its SMS facility is still to be connected to a control device to be able to control the on / off electrical devices remotely.
We have one of the control device which is practical and widely used microcontroller is a chip that serves as an electronic circuit and the controller can store the program inside. The major advantage is tersediannya RAM and microcontroller I / O support, so have a very compact size and more flexibility to be connected and controlling

Study Design

These systems use a serial port connection on your phone’s data connector located on each mobile phone for data exchange with periferalnya like handsfree or a program update purposes, while the microcontroller acts as the processor serial data received from the mobile phone. Communication between the mobile phone (cell phone) with the microcontroller is in serial asynchronous full-duplex nature, meaning that the serial port can send and receive at the same time, for it required an interface to synchronize these devices (ie: phone and mikrokontoler), so both This device can communicate (exchanging data).
In accessing the mobile phone, the microcontroller sends commands AT-Command is a command that begins with the AT + (such as command> (prompt) on DOS), which will be sent by the micro via serial port to order mobile phone to run applications such as reading and sending SMS.
Having established communication, the appliance will detect the presence or not mobile phones, after which the phone will keep on standby and wait for incoming SMS, incoming SMS to a mobile phone will be detected, is a command or not, if not earlier then the SMS will be deleted automatically from phone memory, if the incoming SMS is known of the SMS command line will be encoded by a micro controller and then forwarded to the output device.

Commands that can be recognized by this tool is “XXXXXXXX”: X is the command form of numbers 1 or 0, the value of X represents the desired output; value of 1 means the ignition output (on) and the output value of 0 means the deactivation (off), after executing the command This tool will give a reply to the mobile receiver with the answer “status: XXXXXXXX has been realized ‘and mobile devices back to the standby state to await orders
next.
The design and realization of tools in this paper includes two parts: a design
hardware and software.
The design of the hardware include:
1. Design of control unit microcontroller.
2. The design of the phone to the serial communication
appliance.
3. The design of the output units.

Design of control unit microcontroller

Micro controller is the main module in this case the micro controller strand consists of micro controller IC AT89S51, AT89S51 micro controller oscillator strand, strand AT89S51 micro controller reset. Strand consists of a crystal oscillator and two capacitors. This strand dihubungakan with XTAL1 and XTAL2, used capacitor values of 33 pF and crystal that is used has a value of 11.0592 MHz. strand has the ability to reset the realization of the power-on reset, which is also accompanied with the reset button, this strand consists of a capacitor, a resistor and a push Botton. Value of used 10 UF capacitor resistor values used 8.2 K ?.
PORT 2 of the microstructure is used as the output of the tool, this output will be connected to the relay. PORT 3 of the micro used for a variety of needs in accordance with the usefulness of the port 3.
Use of port 3 are as follows:

- P3.0 (RXD) is used as input from
serial communication between devices with micro.
- P3.1 (TXD) is used as output to
serial communication between a mobile micro

Serial Communications Unit
Communication between the mobile phone by means done serially, with the voltage levels to RS232. Voltage level because of differences between the micro with a serial port data cable cell phones that have been compatible with the RS232 standard, we need a voltage converter. Max232 IC is used as a modifier on the micro-TTL voltage levels to RS232 voltage levels.
Asynchronous communication is done with the amount of data to 8 bits, noparity, and use a baud rate of ± 57 600 bps, used for data transmission facilities that exist on micro controller which is a facility
at 3.0 ports (RXD), port 3.1 (TXD) and GND.

Output Unit
There are eight output channels of the instrument, each output line is connected to a lamp and four lines connected to the relay. Relay is using for 9 V power supply, switching his use of transistors with common emitter configuration. Relay is used as a liaison and an AC circuit breaker, the controller uses the DC current.

Designing Software
At the beginning of the program carried out serial communication initialization, after the existence of mobile phone is detected, the tool will read the contents of incoming SMS inbox on the location of the first and held a long protection against SMS, the SMS are eligible will be encoded, after coded tool, the order will be implemented in PORT 2 outputs on the microcontroller. After the command successfully realized the appliance will send an sms reply to the
sender’s mobile phone which contains the status of the output.
To access the microcontroller used cell phone from AT-COMMAND command.

Evaluation

When we send an SMS command contains 10000000 to activate the first output, the contents of this command is actually berskema SMS 7-bit encoding, because if we are typing a letter or number from the phone keypad means that we have made seven figures 1 / 0 sequence. While the micro data to be processed is a hex number PDU berskema 8 bits and hex numbers from SMS commands such as: 10 million is 31 18 C 6 83 C1 60.
7 bits of data received will be converted to a form of micro berskema 8 hex bits for working on the numbers of micro berskema 8-bit encoding, then converted to ascii and output ports will be moved to microfinance as a result of the output device. After output is realized, micro mobile devices to send commands to send SMS reply containing a status taken from the instruction data stored in RAM.

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