Storing baseline information in EEPROM
Pre-stored no-touch or no-hover (no-event) sensor output values can initially be used when a sensor panel subsystem is first booted up to establish an initial baseline of sensor output values unaffected by fingers or other objects touching or hovering over the sensor panel during boot-up. This initial baseline can then be normalized so that each sensor generates the same output value for a given amount of touch or hover, providing a uniform response across the sensor panel and enabling subsequent touch or hover events to be more easily detected. After the initial normalization process is complete, the pre-stored baseline can be discarded in favor of a newly captured no-event baseline that may be more accurate than the pre-stored baseline due to temperature or other variations.
1. A method for updating baseline sensor output values for a plurality of sensors in a sensor panel, comprising:
performing a scan of the sensor panel to obtain a plurality of sensor output values from the plurality of sensors;
generating baseline sensor output values from the plurality of sensor output values;
determining whether any of the plurality of sensor output values is negative and is less that the baseline sensor output value for that sensor by a first predetermined amount; and
when it is determined that at least one of the plurality of sensor output values is negative and less than the baseline sensor output value for that sensor by the first predetermined amount, recapturing the baseline sensor output values for the plurality of sensors in the sensor panel.
2. The method of claim 1 , wherein the method is performed during boot-up of a sensor panel subsystem.
3. The method of claim 1 , wherein the first predetermined amount is a plurality of standard deviations of background noise below the baseline sensor output value for that sensor.
4. The method of claim 1 , further comprising:
computing a first number of the plurality of sensor output values above the baseline sensor output values,
computing a second number of the plurality of sensor output values below the baseline sensor output values,
determining whether any of the plurality of sensor output values is positive but less than a first threshold, and whether the first number is less than M times the second number; and
when it is determined that at least one of the plurality of sensor output values is positive but less than the first threshold and also that the first number is less than M times the second number, recapturing the baseline sensor output values.
5. The method of claim 4 , wherein the first threshold is a predetermined hover threshold.
6. The method of claim 4 , further comprising:
determining whether any of the plurality of sensor output values is positive but less than the first threshold for a first time period; and
when the plurality of sensor output values is positive but less that the first threshold for the first time period, recapturing the baseline sensor output values.
7. The method of claim 6 , further comprising:
detecting a hovering object; and
when the plurality of sensor output values is positive but less that the first threshold for the first time period and the hovering object is detected, delaying the recapture of the baseline sensor output values.
8. The method of claim 1 , further comprising:
computing a first number of the plurality of sensor output values above the baseline sensor output values,
computing a second number of the plurality of sensor output values below the baseline sensor output values,
determining whether the second number is less than or equal to than the first number by a predetermined margin,
when the second number is less than or equal to the first number by the predetermined margin, re-scanning the sensor panel, and
when the second number is greater than the first number by the predetermined margin, recapturing the baseline sensor output values.
9. A computing system for updating baseline sensor output values for a plurality of sensors in a sensor panel, comprising:
a panel subsystem configured for being communicatively coupled to the sensor panel; and
a processor coupled to the panel subsystem, the processor configured for
performing a scan of the sensor panel to obtain a plurality of sensor output values from the plurality of sensors;
generating baseline sensor output values from the plurality of sensor output values;
determining whether any of the plurality of sensor output values is negative and is less that the baseline sensor output value for that sensor by a first predetermined amount; and
when it is determined that at least one of the plurality of sensor output values is negative and less than the baseline sensor output value for that sensor by the first predetermined amount, recapturing the baseline sensor output values for the plurality of sensors in the sensor panel.
10. The computing system of claim 9 , the processor is further configured for performing the scan during boot-up of a sensor panel subsystem.
11. The computing system of claim 9 , wherein the first predetermined amount is a plurality of standard deviations of background noise below the baseline sensor output value for that sensor.
12. The computing system of claim 9 , the processor further configured for:
computing a first number of the plurality of sensor output values above the baseline sensor output values,
computing a second number of the plurality of sensor output values below the baseline sensor output values,
determining whether any of the plurality of sensor output values is positive but less than a first threshold, and whether the first number is less than M times the second number; and
when it is determined that at least one of the plurality of sensor output values is positive but less than the first threshold and also that the first number is less than M times the second number, recapturing the baseline sensor output values.
13. The computing system of claim 12 , wherein the first threshold is a predetermined hover threshold.
14. The computing system of claim 12 , the processor further configured for:
determining whether any of the plurality of sensor output values is positive but less than the first threshold for a first time period; and
when the plurality of sensor output values is positive but less that the first threshold for the first time period, recapturing the baseline sensor output values.
15. The computing system of claim 14 , the processor further configured for:
detecting a hovering object; and
when the plurality of sensor output values is positive but less that the first threshold for the first time period and the hovering object is detected, delaying the recapture of the baseline sensor output values.
16. The computing system of claim 9 , the processor further configured for:
computing a first number of the plurality of sensor output values above the baseline sensor output values,
computing a second number of the plurality of sensor output values below the baseline sensor output values,
determining whether the second number is less than or equal to than the first number by a predetermined margin,
when the second number is less than or equal to the first number by the predetermined margin, re-scanning the sensor panel, and
when the second number is greater than the first number by the predetermined margin, recapturing the baseline sensor output values.
17. A method for updating baseline sensor output values for a plurality of sensors in a sensor panel, comprising:
generating baseline sensor output values from a plurality of sensor output values; and
recapturing the baseline sensor output values only when at least one of the plurality of sensor output values is negative and less than the baseline sensor output value for that sensor by a first predetermined amount;
determining whether any of the plurality of sensor output values is negative and is less that the baseline sensor output value for that sensor by the first predetermined amount; and
when it is determined that at least one of the plurality of sensor output values is negative and less than the baseline sensor output value for that sensor by the first predetermined amount, recapturing the baseline sensor output values for the plurality of sensors in the sensor panel.
18. The method of claim 17 , wherein the first predetermined amount is a plurality of standard deviations of background noise below the baseline sensor output value for that sensor.