Frequency selection with two frequency sets of multiple operating frequencies in a mutual capacitance sensing devices
View Patent ↗Apparatuses and methods of frequency selection algorithms and frequency set selection are described. One method monitors a signal on the electrodes of a sense network, determine a first group of noise metrics of noise in the signal, determine a second group of noise metrics. The method switches from a first operating frequency in a first set to a second operating frequency in the first frequency set based on the first group of noise metrics and switches from the first operating frequency in the first set to a third operating frequency in a second frequency set based on the second group of noise metrics.
1. A method comprising:
monitoring a signal on a plurality of electrodes of a sense network, the sense network to operate in a first frequency set or a second frequency set, each comprising a plurality of operating frequencies;
determining a first group of one or more noise metrics of noise in the signal;
determining a second group of one or more noise metrics of the noise in the signal;
performing a frequency hop within the first frequency set based on the first group of one or more noise metrics, wherein the frequency hop switches from a first operating frequency to a second operating frequency within the first frequency set; and
performing a frequency set hop from the first frequency set to the second frequency set based on the second group of one or more noise metrics, wherein the frequency set hop switches from the first operating frequency in the first frequency set to an operating frequency in the second frequency set.
2. The method of claim 1 , wherein a first separation in frequencies between the first frequency set and the second frequency set is greater than a second separation in frequencies within the first frequency set.
3. The method of claim 1 , wherein the first frequency set comprises three or more non-overlapping frequency bands, each centered at one of three operating frequencies of the first frequency set.
4. The method of claim 3 , wherein the second frequency set comprises three or more non-overlapping frequency bands, each centered at one of three operating frequencies of the second frequency set.
5. The method of claim 3 , wherein the second frequency set comprises two non-overlapping frequency bands, each centered at one of two operating frequencies of the second frequency set.
6. The method of claim 1 , wherein the switching from the first frequency set to the second frequency set comprises switching from the first operating frequency to one of the plurality of operating frequencies in the second frequency set that is farthest away in frequency from the first operating frequency.
7. The method of claim 1 , wherein the determining the second group of one or more noise metrics comprises:
obtaining a plurality of sub-conversions representing capacitance values measured on the plurality of electrodes;
calculating a third noise metric (NM 3 ) based on the plurality of sub-conversions, wherein the NM 3 represents an energy of the noise in the signal; and
calculating a first noise metric (NM 1 ) based on the plurality of sub-conversions, wherein the NM 1 represents an average sum of absolute value maximums among the sub-conversions in a number of conversions, wherein the second group of one or more noise metrics comprises the NM 1 and the NM 3 ,
wherein the determining the first group of one or more noise metrics comprises calculating a second noise metric (NM 2 ) based on the plurality of sub-conversions, and
wherein the first group of one or more noise metrics comprises the NM 2 and the NM 1 .
8. The method of claim 7 , wherein the calculating the NM 1 , NM 2 , and NM 3 comprises calculating the NM 1 , NM 2 , and NM 3 based on the following equations:
NM
2
=
∑
i
=
1
N
1
N
sub
·
∑
k
=
1
N
sub
SubConvData
i
,
k
∑
i
=
1
N
max
i
(
{
SubConvData
}
)
·
100
,
where N is the number of conversions in a listening scan, SubConvData i,k is the plurality of sub-conversions in each of the number of conversions;
NM
3
=
∑
i
=
1
N
1
N
sub
∑
k
=
1
N
sub
SubConvData
i
,
k
∑
i
=
1
N
max
i
(
{
SubConvData
}
)
·
100
;
and
NM
1
=
1
N
∑
i
=
1
N
max
i
(
{
SubConvData
}
)
.
9. The method of claim 1 , wherein the determining whether the frequency set hop is needed comprises at least one of:
determining that the plurality of operating frequencies in the first set exceed a threshold noise level after a specified number of cycles through the plurality of operating frequencies in the first frequency set; or
determining that a third noise metric (NM 3 ), calculated from a plurality of sub-conversions exceeds a threshold value, wherein the NM 3 represents an energy of the noise in the signal.
10. The method of claim 7 , further comprising:
identifying the plurality of operating frequencies in a current set of the first frequency set and the second frequency set with a minimum noise metric of the NM 2 ;
switching from a current operating frequency of the plurality of operating frequencies in the current set to the operating frequency with the minimum noise metric of the NM 2 ; and
determining whether a frequency set hop from the current set to another set is needed based on the first group of one or more noise metrics regardless of the NM 2 in the current set.
11. A capacitance sensing system, comprising:
a memory device; and
a controller coupled to the memory device, wherein the controller is configured to receive a signal from a sense network comprising a plurality of electrodes to detect a conductive object proximate to the plurality of electrodes, wherein the controller comprises:
a noise listening circuit configured to:
determine a first group of one or more noise metrics of noise in the signal; and
determine a second group of one or more noise metrics of the noise in the signal; and
a frequency selection state machine configured to:
perform a frequency hop within a first frequency set based on the first group of the one or more noise metrics, wherein the frequency hop switches from a first operating frequency in the first frequency set to a second operating frequency in the first frequency set; and
perform a frequency set hop from the first frequency set to a second frequency set based on the second group of the one or more noise metrics, wherein the frequency set hop is switches from the first operating frequency in the first frequency set to an operating frequency in the second frequency set.
12. The capacitance sensing system of claim 11 , wherein a first separation in frequencies between the first frequency set and the second frequency set is greater than a second separation in frequencies within the first frequency set.
13. The capacitance sensing system of claim 11 , wherein the first frequency set comprises three or more non-overlapping frequency bands, each centered at one of three operating frequencies of the first frequency set, and wherein the second frequency set comprises two or more non-overlapping frequency bands, each centered at one of two operating frequencies of the second frequency set.
14. The capacitance sensing system of claim 11 , wherein the noise listening circuit is configured to:
obtain a plurality of sub-conversions representing capacitance values measured on the plurality of electrodes;
calculate a third noise metric (NM 3 ) based on the plurality of sub-conversions, wherein the NM 3 represents an energy of the noise in the signal;
calculate a first noise metric (NM 1 ) based on the plurality of sub-conversions, wherein the NM 1 represents an average sum of absolute value maximums among the sub-conversions in a number of conversions; and
calculate a second noise metric (NM 2 ) based on the plurality of sub-conversions,
wherein the second group of one or more noise metrics comprises the NM 1 and the NM 3 , and
wherein the first group of one or more noise metrics comprises the NM 2 and the NM 1 .
15. The capacitance sensing system of claim 14 , wherein the noise listening circuit is configured to calculate the NM 1 , NM 2 , and NM 3 based on the following equations:
NM
2
=
∑
i
=
1
N
1
N
sub
·
∑
k
=
1
N
sub
SubConvData
i
,
k
∑
i
=
1
N
max
i
(
{
SubConvData
}
)
·
100
,
where N is the number of conversions in a listening scan, SubConvData i,k is the plurality of sub-conversions in each of the number of conversions;
NM
3
=
∑
i
=
1
N
1
N
sub
∑
k
=
1
N
sub
SubConvData
i
,
k
∑
i
=
1
N
max
i
(
{
SubConvData
}
)
·
100
;
and
NM
1
=
1
N
∑
i
=
1
N
max
i
(
{
SubConvData
}
)
.
16. The capacitance sensing system of claim 11 , wherein the noise listening circuit is configured to switch from the first operating frequency to an operating frequency in the second frequency set that is farthest away in frequency from the first operating frequency, when performing the frequency set hop.
17. A host device, comprising:
a display;
a capacitance sensing array disposed in connection with the display;
a touch screen controller coupled to the capacitance sensing array, wherein the touch screen controller comprises:
a capacitance sensing circuit coupled to the capacitance sensing array; and
a noise listening circuit coupled to the capacitance sensing array, wherein the noise listening circuit is configured to:
determine a first group of one or more noise metrics of noise in a signal;
determine a second group of one or more noise metrics of the noise in a signal;
perform a frequency hop within a first frequency set based on the first group of the one or more noise metrics, wherein the frequency hop switches from a first operating frequency in a first frequency set to a second operating frequency in the first frequency set; and
performing a frequency set hop from the first frequency set to a second frequency set based on the second group of the one or more noise metrics, wherein the frequency set hop switches from the first operating frequency in the first frequency set to an operating frequency in the second frequency set.
18. The host device of claim 17 , wherein the first frequency set comprises three or more non-overlapping frequency bands, each centered at one of three operating frequencies of the first frequency set, and wherein the second frequency set comprises two or more non-overlapping frequency bands, each centered at one of two operating frequencies of the second frequency set.
19. The host device of claim 17 , wherein the noise listening circuit is configured to switch from the first operating frequency in the first frequency set to an operating frequencies in the second frequency set that is farthest away in frequency from the first operating frequency when performing the frequency set hop.