rolling code remote control decoder

The principle of rolling code is roughly this:

 

1. The rolling code is a pseudo-random code with a long period. For example, 240 means that the length of the code is 40 bits. Now the code length of most car keys is longer than 40bit;

2. The current rolling code is stored in the car key. When the car key is pressed, the rolling code plus a function code (such as unlocking, unlocking, or opening the trunk) is sent to the car together;

3. The car also has the current rolling code. When the car receives the same rolling code, it performs operations such as unlocking accordingly. If the received codes do not match, it does nothing;

4. The car key and the rolling code in the car are synchronized;

5. When the car key is far away from the car, someone accidentally presses the car key several times, and the random code of the car key will advance several steps, and at this time, it will not be synchronized with the code in the car. To solve this problem, the car is allowed to receive hundreds of codes after the current code. As long as the code sent by the car key is within this window, the car is considered valid;

6. If the car key is pressed incorrectly more than a few hundred times, the car key and the car will completely lose synchronization. At this time, you can only find a way to restore synchronization.