Patent ID: 7698091

Claim:
A method for detecting the start of a dive for a portable electronic device having at least one first operating mode and one second operating mode, called the dive mode, and including a pressure sensor for measuring a value of ambient pressure as well as electronic circuits for processing the results of said measurements including a time base and at least a memory zone, the method implemented in said first operating mode, including the steps of: a) periodically measuring an ambient pressure value at a first frequency, b) storing said ambient pressure value as a reference pressure in said memory zone at a second frequency lower than said first frequency, c) periodically calculating a first pressure variation value between the measured ambient pressure and the reference pressure at said first frequency and comparing said first pressure variation value to a predefined value, called the trigger threshold and stored in said memory zone, d) activating said dive mode if said first pressure variation value is higher than said trigger threshold or, in the opposite case, continuing to the next step e, e) calculating, at a third frequency, a second pressure variation value between the last two measured values of the ambient pressure and comparing said second pressure variation value to a predefined magnitude, or a mean pressure value determined on the basis of measured pressure values, stored in said memory zone, said magnitude or said mean pressure value being lower than said trigger threshold, said third frequency being less than or equal to said first frequency, f) returning to step a) if said second pressure variation value is less than or equal to said magnitude or, in the opposite case, implementing a dive start check loop comprising the operations of: storing said reference pressure value as a backup reference pressure value, returning to steps a) to d) for a predetermined period of time during which the stored reference pressure value is replaced by said backup reference pressure value if said dive mode is activated in step d), and returning as normal to steps a) to f) once said predetermined period of time has elapsed.