Or relating to storage of accelerometer data
A method of storing data relating to a parameter of a vehicle, wherein the data is provided by a vehicle sensor. The method includes the steps of: receiving, at time intervals, a series of first and second values from the vehicle sensor. The method further includes steps of processing the first and second values in a manner to reduce the processor requirements and memory for processing the first and second values.
1. A method of storing data relating to a parameter of a vehicle, wherein the data is provided by a vehicle sensor, the method comprising the steps of:
receiving, at time intervals, a series of first and second values from the vehicle sensor, wherein each of the first value represents the parameter that is sensed by the vehicle sensor, and each of the second values relates to functioning of the vehicle sensor;
for each of the first values that is received comprising a new first value:
comparing the new first value to an immediately preceding first value that was received;
if a difference between the new first value and the immediately preceding first value is below a first difference threshold, storing the difference in a memory; or
if the difference between the new first value and the immediately preceding first value is above a second difference threshold, storing the new first value in the memory,
maintaining a counter recording the number of consecutive of the second values that have been received that have had the same value; and
for each second values that is received comprising a new second value:
comparing the new second value to an immediately preceding second value that was received;
if the new second value is the same as the immediately preceding second value, incrementing the counter; or
if the new second value is different from the immediately preceding second value, recording a single bit representing the immediately preceding second value in the memory, along with a current counter value in a data field with the single bit representing the immediately preceding second value, and then resetting the counter; and
if the counter has reached a counter threshold value, recording another single bit representing the new second value in the memory, along with the counter threshold value in another data field with the single bit representing the new second value, and resetting the counter,
wherein each of the second values has one of: a validity flag value representing the vehicle sensor being functional, or a different value representing the vehicle sensor being non-functional.
2. The method according to claim 1 , wherein:
the step of storing the difference between the new first value and the immediately preceding first value comprises storing a data word having a first length;
the step of storing the new first value comprises storing a data word having a second length; and
the first length is less than the second length.
3. The method according to claim 1 , wherein the step of storing the new first value comprises storing a data word including one or more bits that indicate that the data word includes the new first value.
4. The method according to claim 1 , wherein the step of storing the difference between the new first value and the immediately preceding first value comprises storing a data word including one or more bits that indicate that the data word includes the difference between two consecutive first values.
5. The method according to claim 3 , wherein the one or more bits comprise a header which appears at the start of the data word.
6. The method according to claim 1 , further comprising the step of recording timestamp data indicating the time at which the data relating to the parameter of the vehicle has been stored, and further comprising the step of recording separate timestamp data in connection with the first values and in connection with the second values.
7. The method according to claim 1 , further comprising the steps of:
recording timestamp data at periodic intervals in connection with the second values; and
if, following an interval since the recording of a previous timestamp data, the counter is in the course of incrementing, waiting until data relating to the second values is recorded before recording the timestamp data in connection with the second values.
8. The method according to claim 1 , further comprising the steps of receiving from the vehicle sensor a data package comprising the new first value and the new second value; and separating the new first value and the new second value.
9. The method according to claim 1 , wherein: recording the immediately preceding second value in the memory, along with the current counter value, comprises storing a data word in the memory including the immediately preceding second value and the current counter value; and wherein recording the new second value in the memory, along with the counter threshold value, comprises storing a data word in the memory including the new second value and the counter threshold value.
10. The method according to claim 1 , further comprising recording the first and second values in the memory of the vehicle and storing the first and the second values relating to a set time period immediately preceding a present moment, and over-writing the first and the second values relating to times which are more than the set time period before the present moment.
11. A non-transitory computer-readable storage medium storing program code operable to perform all of the steps of claim 1 when the program code is run on a computer.
12. A vehicle having a vehicle sensor which, in use, generates a series of first and second values from the vehicle sensor, wherein each of the first values represents a parameter that is sensed by the vehicle sensor, and each of the second values relate to the functioning of the vehicle sensor,
wherein the first and the second values are transmitted from the vehicle sensor to a vehicle processor, and stored in a memory of the vehicle the processor, and wherein the vehicle processor is configured for:
receiving, at time intervals, a series of first and second values from the vehicle sensor, wherein each of the first value represents the parameter that is sensed by the vehicle sensor, and each of the second value relates to functioning of the vehicle sensor;
for each of the first values that is received comprising a new first value:
comparing the new first value to an immediately preceding first value that was received;
if a difference between the new first value and the immediately preceding first value is below a first difference threshold, storing the difference in the memory; or
if a difference between the new first value and the immediately preceding first value is above a second difference threshold, storing the new first value in the memory,
maintaining a counter recording the number of consecutive of the second values that have been received that have had the same value; and
for each second values that is received comprising a new second value:
comparing the new second value to an immediately preceding second value that was received;
if the new second value is the same as the immediately preceding second value, incrementing the counter; or
if the new second value is different from the immediately preceding second value, recording a single bit representing the immediately preceding second value in the memory, along with a current counter value in a data field with the single bit representing the immediately preceding second value, and then resetting the counter; and
if the counter has reached a counter threshold value, recording another single bit representing the new second value in the memory, along with the counter threshold value in another data field with the single bit representing the new second value, and resetting the counter,
wherein each of the second values has one of: a validity flag value representing the vehicle sensor being functional, or a different value representing the vehicle sensor being non-functional.
13. The vehicle according to claim 12 , wherein the series of the first and the second values comprises a series of linked first and second values.
14. The vehicle according to claim 12 , wherein the sensor is an accelerometer, and the sensors.