System and method for MEMS sensor system synchronization
Various aspects of this disclosure comprise systems and methods for synchronizing sensor data acquisition and/or output. For example, various aspects of this disclosure provide for achieving a desired level of timing accuracy in a MEMS sensor system, even in an implementation in which timer drift is substantial.
1. An integrated sensor having an adjustable sensor output data rate (ODR), wherein the sensor has an internal sensor sync clock, is configured to output measurements at an ODR established by the internal sensor sync clock, and comprises a processor operable to, at least:
receive a first sync signal from an external source;
receive a second sync signal from the external source;
determine, based at least in part on the internal sensor sync clock, a time differential between the received first sync signal and the received second sync signal;
determine an adjustment to the ODR based, at least in part, on the determined time differential; and
modify operation of the sensor by applying the determined adjustment to the ODR, so that subsequent sensor measurements are provided at the adjusted ODR.
2. The integrated sensor of claim 1 , wherein at least one period of the adjusted ODR corresponds to the determined time differential.
3. The integrated sensor of claim 1 , wherein the adjusted ODR aligns output measurements from the sensor with sync signals expected from the external source.
4. The sensor of claim 3 , wherein a delay between reception of a sync signal from the external source and the output of a measurement is a predetermined number of internal clock signal cycles.
5. The integrated sensor of claim 1 , wherein the adjustment to the ODR comprises an adjustment to the internal sensor sync clock based on the determined time differential.
6. The integrated sensor of claim 5 , wherein a frequency of the internal sync clock and/or a divide-by value is modified based, at least in part, on the adjustment to the internal sensor sync clock.
7. The integrated sensor of claim 1 , wherein the processor is operable to:
upon reception of the first sync signal, store a first counter value;
upon reception of the second sync signal, store a second counter value; and
determine the time differential between the first sync signal and the received second sync signal based, at least in part, on a difference between the first and second stored counter values.
8. The integrated sensor of claim 1 , wherein the processor is operable to receive information about an expected time differential.
9. The integrated sensor of claim 8 , wherein the expected time differential is received from the external source.
10. The integrated sensor of claim 1 , wherein the external source provides the first and second sync signals when an application is initiated.
11. The integrated sensor of claim 1 , wherein the first and second sync signals are generated upon a determination that enhanced sensor synchronization is desired.
12. The integrated sensor of claim 1 , wherein the first and second sync signals are generated for image stabilization.
13. The integrated sensor of claim 1 , wherein the integrated sensor receives input measurements from at least one additional sensor and outputs the received input measurements from the at least one additional sensor at the adjusted ODR.
14. The integrated sensor of claim 1 , wherein the integrated sensor is a motion sensor.
15. A method for adjusting a sensor output data rate (ODR), wherein measurements from a sensor are output at an ODR established by the internal sensor sync clock of the sensor, comprising:
receiving a first sync signal from an external source;
receiving a second sync signal from the external source;
determining, based at least in part on the internal sensor sync clock, a time differential between the received first sync signal and the received second sync signal;
determining an adjustment to the ODR based, at least in part, on the determined time differential; and
modifying operation of the sensor by applying the determined adjustment to the ODR, so that subsequent sensor measurements are provided at the adjusted ODR.
16. The method of claim 15 , wherein at least one period of the adjusted ODR corresponds to the determined time differential.
17. The method of claim 15 , wherein the adjusted ODR aligns output measurements from the sensor with sync signals expected from the external source.
18. A portable device comprising:
a host processor;
an external clock source; and
an integrated sensor having an adjustable sensor output data rate (ODR), wherein the sensor has an internal sensor sync clock, is configured to output measurements at an ODR established by the internal sensor sync clock, and comprises at least one sensor processor operable to, at least:
receive a first sync signal from the external clock source;
receive a second sync signal from the external clock source;
determine, based at least in part on the internal sensor sync clock, a time differential between the received first sync signal and the received second sync signal;
determine an adjustment to the ODR based, at least in part, on the determined time differential; and
modify operation of the sensor by applying the determined adjustment to the ODR, so that subsequent sensor measurements are provided at the adjusted ODR to the host processor.