GSM Vehicle Control and Security System using SMS

I did this project for my 5th semester for "Microcontroller based Systems". It was done on an 89C51 microcontroller which belongs to 8051 family, using a sony ericsson T290i mobile inter-connected with a serial cable. It was implemented on my Honda Civic.
The user could control some functions of the vehicle by sending
specific sms commands to the T2920i.

Some of these functions were:

• start and stop the engine (without using the key)
• stop the engine if somebody starts it with a key ( by cutting off ignition)
•  lock and unlock the doors
•  send a text message to the owner if an intruder is detected (by monitoring the doors)
•  switch the heater/air conditioner on and off

DESCRIPTION

SMS is checked by monitoring the phone memory by using AT+CPMS command which sets the preferred phone memory location for storing sms and returns status of phone memory.

When an SMS is received its text is dumped into microcontroller's RAM using a very calibrated approach. Therefore the 7th character(7th was chosen randomly) always lands at location 57H of RAM. This was determined by connecting the phone to PC's serial port and debugging using the Proteus Simulation. The RAM was monitored as the phone sent the SMS text and it was dumped.

So the 7th character is compared using the below table and the appropriate function is called for performing the action using relays.



############## SMS COMMANDS ###################

 SMS COMMAND         7TH CHARACTER                HEX EQUIVALENT

start engine                                     e                                       65h    
stop engine                                     n                                       6eh    
car lock                                            c                                       63h    
car unlock                                        l                                        6ch    
on heater                                         t                                        74h    
off heater                                         a                                       61h    
panic mode                                    m                                       6dh    

Two Interrupts are used, Timer 0 overflow interrupt and External interrupt. The program checks for sms every time Timer 0 overflows. External Interrupt is connected to door switch for detecting intrusion and sending sms to owner. If external interrupt happens while sms is being checked, the program will get stuck due to unexpected reply from mobile. To avoid this situation, both interrupts are set to high priority using IT0 bit in TCON register. Now if one Interrupt occurs while the other is being serviced, it will have to wait until control returns from first interrupt.      

Here are the Hardware connections.

 P0.0 = for locking car (attached to security sys remote)
 P0.1 = for unlocking car (attached to security sys remote)
 P0.2 = for switching on heater
 P0.3 = connected to IGNITION RELAY 1 (CRANK or START engine)
 P0.4 = connected to IGNITION RELAY 2 (ON)
 P0.5 = connected to IGNITION RELAY 3 (ACC)
 P0.6 = connected to IGNITION CUT RELAY (Used for switching off engine when someone is running with your car!! i.e PANIC MODE)
 P3.2(INT0) = Door switch relay(for detecting if door is opened) 

Download Section

Here are the project files:
-Source code (Assembly language-Compiler: Keil uVision 3)
-Proteus Simulation  (works with Proteus 7.4 and above)
-Sony Ericsson AT command manual

Hardware:

-PCB Layout 8051 board  (works with Proteus 7.4 and above)
-Relay board demo (simulation) (works with Proteus 7.4 and above)
-Custom Serial adapter 
(The custom serial adapter as seen in the last picture; connected between the mobile phone serial cable and 8051 board, is used to provide power to the MAX232 IC present inside the mobile phone serial cable by giving +5V at pins 7(RTS) and 4(DTR) of the phone serial cable. The cable won't work without this custom adapter)

Some snapshots of the hardware. From the pictures it may seem that the project is incomplete or something but I actually drove the car around for a couple of months with the system working!

The setup was placed in the dashboard

The relays connected to the ignition

The microcontroller board with the serial port and the relay board.

 The 8051 board connected to the phone through serial cable.

The code has been tidied before uploading so if you can interpret it, it can be ported easily to an AVR or PIC. If anybody wants any help with this stuff, just drop a comment or "Contact me". I'll be happy to help.