Tire pressure monitoring system transmission protocol
View Patent ↗A system for monitoring conditions within a tire includes a sensor assemblies ( 14 ). The sensor assemblies ( 14 ) emit a transmission ( 26 ) containing information indicative of conditions within a tire to a receiver ( 16 ). The transmission ( 26 ) from the sensor assemblies ( 14 ) includes an amplitude shift key wake up portion and various data packet portions. The data packet portions are separated by a variable interval to prevent collisions of transmissions at the receiver.
1. A method of transmitting information indicative of conditions within a tire comprising the steps of:
a. transmitting a signal including an amplitude shift keyed transmission preamble to a receiver;
b. transmitting a frequency shift keyed (FSK) identification code from a first transmitter;
c. transmitting a fsk signal indicative of pressure within the tire from the first transmitter;
d. transmitting a fsk signal indicative of temperature within the tire from the first transmitter,
e. varying a time interval between portions of said identification code, said signal indicative of pressure within the tire, and said signal indicative of temperature within the tire; and
f. receiving one of a frequency shift keyed (FSK) identification code, an FSK signal indicative of pressure within a tire, and an FSK signal indicative of a temperature within a tire from a second transmitter within the time interval between portions of any of the FSK signals from the first transmitter.
2. The method of claim 1 , wherein said step of varying said time interval includes transmitting a length of the interval to a receiver such that the receiver prepares to receive a next data packet at the communicated time interval.
3. The method of claim 2 , wherein said time interval varies in response to vehicle operating parameters.
4. The method of claim 3 , wherein said operating parameter includes vehicle speed, and a frequency of said transmissions are increased in response to an indication of pressure loss at a pre-selected rate.
5. The method of claim 4 , wherein said frequency of said transmissions are decreased in response to a vehicle not moving for a set period.
6. The method of claim 5 , wherein said frequency of said transmissions varies according to vehicle speed.