Remote computer RESET using a mobile phone

Back in 2006, I was asked to make a device that allows you to remotely, using a mobile phone, perform a RESET server. At that time, I worked closely with Microchip PIC controllers, and I already had enough knowledge of circuit design to solve this problem, even if not very professionally, but on my own.

How it works

To work, you need a simple mobile phone configured to automatically pick up the phone when you call. A mono headset is connected to the phone. The signals from the headset speaker go to the input device, and from the device are signals to the headset microphone. To reset the server, a person calls the device’s phone from any other phone that supports touch-tone dialing (DTMF). After picking up the handset, the user enters a command code and password from his phone. If the password is correct, the device closes the contacts of the computer's RESET lines for a few milliseconds, i.e. imitates manual pressing of the RESET button - the server restarts. If everything went well, the device responds with a pulse of a certain frequency that the user hears in its dynamics.

Available DTMF commands

1. Computer RESET - password # 01 #
2. Change Password - password # 02 # new_password #

where password and new_password are six-digit numbers (after flashing the microcontroller, the default password is 012345).
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Device layout

Key elements

1. MT8870DE tone pulse decoder , which allows you to digitally receive the codes of buttons pressed by callers on your phone.
2. Microcontroller PIC18F1320-I / P with DTMF command processing and execution program.
3. Optorele KR293KP4B , directly closing the contacts of the controlled device.

Cost of

At a cost, the device cost me about 1,400 rubles + a SIM card to the phone:

• mobile phone with headset - 800 rubles.;
• DTMF decoder - 35 rubles;
• microcontroller - 100 rubles;
• optorele - 50 rubles;
• power supply switching 220V / 5V 1,7A - 280 rubles;
• “Crumbling” - 135 rubles.

Links

Readable device layout
Source codes of the program with a hex file for microcontroller firmware