Hi all,
I'm working on a project at the moment in my car, and the only OEM electronic component remaining in the car is the radio/cd player - so the OEM central locking is gone.
I still wish to retain central locking, and am looking for some guidance. I'm using a passive RFID system that uses an RFID card inserted into a dash slot to determine who the driver is, i.e owner or valet driver. When the RFID tag is inserted, the starter button is also live, so no 'key' itself is needed.
However, I want my central locking to work from a good distance of ~10m still. What sort of hardware am I looking at to achieve this? I believe active RFID is still quite costly, so I presume it'll be traditional RF radio type hardware.
I'll be doing the PCB myself to fit into my own fob, so general guidance of component choice is what I'm after, and how I go about getting three buttons to transmit different signals (i.e. lock, unlock, boot open etc). Importantly of course, is security - how do I go about encrypting the signal etc? (although I believe many existing keyless entry systems just use a rolling algorithm that uses the next code out of the available each time, +- 100, hence why pressing the button over a 100 times out of range stops the fob working. Also, to prevent brute force - don't allow recieving codes to unlock the doors, even if correct if more than 20 different codes were received in 1 sec, to prevent brute force attacks)
I.e. do I need an MCU inside the fob, which sends signals to an RF transmitter chip prior to broadcast? Everything I've done before has been wired, so I'm very unversed in the world of wireless.
Could I actually use a radio system to determine who the driver is as opposed to my current passive RFID system? This of course all needs to interface to an AVR microcontroller in my dash, using the UART serial.
Many thanks in advance.