Touchscreen device with non-orthogonal electrodes
Some embodiments include a touchscreen device (e.g., a projected capacitive sensor) with non-orthogonal U-drive and V-sense electrodes that intersect at an acute angle, θ. The touchscreen device includes a rectangular touch sensitive area with horizontal edge of length W and a vertical edge of length H. Some embodiments include a controller coupled to the touchscreen device that transmits signals via N drive channels, where N is an integer, where the N drive channels are communicatively coupled to P U-drive electrodes, and where P is an integer greater than or equal to N. Members of a subset of the P U-drive electrodes communicatively coupled to one of the N drive channels, intersect mutually exclusive sets of the V-sense electrodes. Motivated by signal-to-noise ratio considerations, values of acute angle, θ, are chosen such that signals corresponding to the drive signals traverse path lengths that are less than W plus H.
1. A touchscreen system comprising:
a touchscreen device comprising U-drive electrodes and V-sense electrodes that intersect at an acute angle, θ, and having a rectangular touch sensitive area with horizontal edge of length (W) and a vertical edge of length (H); and
a controller coupled to the touchscreen device, configured to:
transmit drive signals via N drive channels, where N is an integer, wherein the N drive channels are communicatively coupled to P U-drive electrodes,
where P is an integer greater than or equal to N,
wherein members of a subset of the P U-drive electrodes communicatively coupled to one of the N drive channels, intersect mutually exclusive sets of the V-sense electrodes; and
wherein based on a value of θ, signals corresponding to the drive signals traverse path lengths that are less than W plus H,
wherein θ D comprises an acute angle between the vertical edge and a V-sense electrode of the V-sense electrodes, and wherein φ=0,
wherein θ D comprises an angle between the vertical edge and a diagonal of the rectangular touch sensitive area, and wherein 0°<θ<θ D , and
wherein a quantity,
(
1
+
R
2
)
cos
(
θ
)
is greater than one, wherein aspect ratio, R, equals tan(θ D ).
2. The touchscreen system of claim 1 , wherein the path lengths corresponding to the drive signals are less than H plus half of W.
3. The touchscreen system of claim 1 , wherein a pitch of the U-drive electrodes is less than a pitch of the V-sense electrodes.
4. The touchscreen system of claim 3 , wherein the pitch of the U-drive electrodes is sin(θ) times the pitch of the V-sense electrodes.
5. A method for a controller coupled to a touchscreen device, wherein the touchscreen device comprises U-drive electrodes and V-sense electrodes that intersect at an acute angle, θ, and a rectangular touch sensitive area with horizontal edge of length W and a vertical edge of length H, the method comprising:
transmitting drive signals via N drive channels, where N is an integer, wherein the N drive channels are communicatively coupled to P U-drive electrodes,
where P is an integer greater than or equal to N,
wherein members of a subset of the P U-drive electrodes communicatively coupled to one of the N drive channels intersect mutually exclusive sets of the V-sense electrodes; and
receiving measurements in response to the drive signals via the V-sense electrodes, wherein based on a value of θ, the measurements correspond to signals traversing path lengths that are less than W plus H,
wherein θ D comprises an angle between the vertical edge and a diagonal of the rectangular touch sensitive area, wherein 0°<θ<θ D ; and wherein 0°<φ<arctan(W/(2H)), wherein φ comprises an acute angle between the vertical edge and V-sense electrodes, and
wherein a quantity,
(
1
+
R
2
)
2
cos
ϕ
max
(
1
cos
2
ϕ
,
1
cos
2
(
θ
-
ϕ
)
)
is greater than one, wherein aspect ratio, R, equals tan(θ D ).
6. The method of claim 5 , wherein a pitch of the U-drive electrodes is less than a pitch of the V-sense electrodes.
7. The method of claim 6 , wherein the pitch of the U-drive electrodes is sin(θ) times the pitch of the V-sense electrodes.
8. A non-transitory computer-readable medium storing instructions that, when executed by a controller coupled to a touchscreen device, cause the controller to perform operations, wherein the touchscreen device comprises U-drive electrodes and V-sense electrodes that intersect at an acute angle, θ, and a rectangular touch sensitive area with horizontal edge of length W and a vertical edge of length H, the operations comprising:
transmitting drive signals via N drive channels, where N is an integer, wherein the N drive channels are communicatively coupled to P U-drive electrodes,
where P is an integer greater than or equal to N,
wherein members of a subset of the P U-drive electrodes communicatively coupled to one of the N drive channels intersect mutually exclusive sets of the V-sense electrodes; and
receiving measurements in response to the drive signals via the V-sense electrodes, wherein based on a value of θ, the measurements correspond to signals that traverse path lengths that are less than W plus H,
wherein φ comprises an acute angle between the vertical edge and a V-sense electrode of the V-sense electrodes, and wherein φ=0,
wherein θ D comprises an angle between the vertical edge and a diagonal of the rectangular touch sensitive area, and wherein 0°<θ<θ D , and
wherein a quantity,
(
1
+
R
2
)
cos
(
θ
)
1
sin
θ
is greater than one, wherein aspect ratio, R, equals tan(θ D ).
9. The non-transitory computer-readable medium system of claim 8 , wherein a pitch of the V-sense electrodes is less than a pitch of the U-drive electrodes.
10. The non-transitory computer-readable medium of claim 9 , wherein the pitch of the V-sense electrodes is sin(θ) times the pitch of the U-drive electrodes.