Touch screen and method of compensating for differences in routing trace path lengths

1. A touch sensitive input device comprising:

a touch panel including a plurality of transmit lines and a plurality of receive lines arranged with the plurality of transmit lines in a grid pattern, such that a sense node is disposed on the touch panel at each intersection of the transmit and receive lines;

wherein a first subset of the transmit lines are coupled to routing traces on only a first side of the touch panel;

wherein a second subset of the transmit lines are coupled to routing traces on only a second side of the touch panel; and

wherein a third subset of the transmit lines are coupled to routing traces on both the first side and the second side of the touch panel; and

a processing device configured to execute program instructions to compensate for offsets in digital signals corresponding to sense nodes associated with the first subset of transmit lines and sense nodes associated with the second subset of transmit lines, wherein the program instructions comprise:

a first set of program instructions executable to determine a first offset value by determining a difference between an average value of the digital signals corresponding to sense nodes associated with the first subset of transmit lines and an average value of digital signals corresponding to sense nodes associated with the third subset of transmit lines; and

a second set of program instructions executable to determine a second offset value by determining a difference between an average value of the digital signals corresponding to sense node associated with the second subset of transmit lines and an average value of the digital signals corresponding to sense nodes associated with the third subset of transmit lines.

2. The touch sensitive input device as recited in claim 1 , wherein the third subset of the transmit lines is disposed on the touch panel between the first and second subsets of the plurality of transmit lines.

3. The touch sensitive input device as recited in claim 1 , wherein the plurality of receive lines are coupled to routing traces on a third side of the touch panel.

4. The touch sensitive input device as recited in claim 3 , further comprising transmit circuitry coupled to supply drive signals to the plurality of transmit lines via the routing traces on the first side and the second side of the touch panel.

5. The touch sensitive input device as recited in claim 3 , further comprising:

receive circuitry coupled to receive analog signals corresponding to each sense node on the touch panel from the routing traces on the third side of the touch panel, wherein the receive circuitry is configured to convert the analog signals into digital signals; and

a storage medium coupled to the receive circuitry and configured to store the digital signals in a memory table having rows and columns, wherein:

a first subset of the rows comprises the digital signals corresponding to the sense node associated with the first subset of transmit lines;

a second subset of the rows comprises the digital signals corresponding to the sense node associated with the second subset of transmit lines; and

a third subset of the rows comprises the digital signals corresponding to the sense node associated with the third subset of transmit lines.

6. The touch sensitive input device as recited in claim 5 , wherein the processing device is coupled to the storage medium and configured to execute:

the first set of program instructions to determine the first offset value by determining a difference between an average value of the digital signals stored within the first subset of rows and an average value of the digital signals stored within the third subset of rows;

the second set of program instructions to determine the second offset value by determining a difference between an average value of the digital signals stored within the second subset of rows and the average value of the digital signals stored within the third subset of rows; and

a third set of program instructions executable to compensate for offsets in the digital signals stored within the first and second subsets of rows in the memory table by:

applying the same first offset value to each of the digital signals stored within the first subset of rows; and

applying the same second offset value to each of the digital signals stored within the second subset of rows.

7. A method, comprising:

supplying drive signals to a plurality of transmit lines disposed on a touch panel;

receiving sense signals corresponding to sense nodes disposed on the touch panel from a plurality of receive lines disposed on the touch panel;

digitizing the received sense signals; and

adjusting the digital sense signals by:

applying the same first offset value to each digital sense signal corresponding to sense nodes associated with a first subset of the transmit lines, which are coupled to routing traces on only a first side of the touch panel; and

applying the same second offset value to each digital sense signal corresponding to sense nodes associated with a second subset of the transmit lines, which are coupled to routing traces on only a second side of the touch panel, wherein the second offset value is different in value from the first offset value.

8. The method as recited in claim 7 , further comprising using the adjusted digital sense signals to detect a location of a touch event on the touch panel.

9. The method as recited in claim 7 , further comprising storing the digital sense signals in a memory table having rows and columns, wherein the step of storing the digital sense signals in the memory table comprises:

storing the digital sense signals corresponding to the sense node associated with the first subset of the transmit lines, which are coupled to routing traces on only the first side of the touch panel, within a first subset of rows in the memory table;

storing the digital sense signals corresponding to the sense node associated with the second subset of the transmit lines, which are coupled to routing traces on only the second side of the touch panel, within a second subset of rows in the memory table; and

storing digital sense signals corresponding to sense node associated with a third subset of transmit lines, which are coupled to routing traces on both the first side and the second side of the touch panel, within a third subset of the rows in the memory table.

10. The method as recited in claim 9 , wherein the step of adjusting the digital sense signals stored in the memory table further comprises:

determining the first offset value by determining a difference between an average value of the digital sense signals stored within the first subset of rows and an average value of the digital sense signals stored within the third subset of rows;

determining the second offset value by determining a difference between an average value of the digital sense signals stored within the second subset of rows and an average value of the digital sense signals stored within the third subset of rows.

11. An information handling system, comprising:

a touch panel including a plurality of transmit lines and a plurality of receive lines arranged with the plurality of transmit lines in a grid pattern, such that a sense node is disposed on the touch panel at each intersection of the transmit and receive lines, wherein:

a first subset of the transmit lines are coupled to routing traces on only a first side of the touch panel;

a second subset of the transmit lines are coupled to routing traces on only a second side of the touch panel; and

a third subset of the transmit lines are coupled to routing traces on both the first side and the second side of the touch panel; and

a touch controller coupled to the touch panel for supplying drive signals to the plurality of transmit lines, receiving sense signals corresponding to the sense nodes from the plurality of receive lines, digitizing the received sense signals and storing the digital sense signals;

wherein the touch controller is configured to compensate for offsets in the stored digital sense signals by:

determining a first offset value by determining a difference between an average value of the stored digital sense signals corresponding to sense nodes associated with the first subset of transmit lines and an average value of stored digital sense signals corresponding to sense nodes associated with the third subset of transmit lines; and

determining a second offset value by determining a difference between an average value of the stored digital sense signals corresponding to sense nodes associated with the second subset of transmit lines and an average value of the stored digital sense signals corresponding to sense nodes associated with the third subset of transmit lines;

applying the same first offset value to each of the stored digital sense signals corresponding to sense nodes associated with the first subset of the plurality of transmit lines; and

applying the same second offset value to each of the stored digital sense signals corresponding to sense nodes associated with the second subset of the plurality of transmit lines, wherein the second offset value is different in value from the first offset value.

12. The information handling system as recited in claim 11 , wherein the touch controller comprises transmit circuitry coupled to supply the drive signals to the plurality of transmit lines via the routing traces on the first side and the second side of the touch panel.

13. The information handling system as recited in claim 11 , wherein the touch controller comprises receive circuitry coupled to receive the sense signals and configured to convert the sense signals into the digital sense signals.

14. The information handling system as recited in claim 11 , wherein the touch controller comprises a storage medium coupled to store the digital sense signals in a memory table having rows and columns, wherein:

a first subset of the rows comprises the stored digital sense signals corresponding to the sense node associated with the first subset of transmit lines;

a second subset of the rows comprises the stored digital sense signals corresponding to the sense node associated with the second subset of transmit lines; and

a third subset of the rows comprises the stored digital sense signals corresponding to the sense node associated with the third subset of transmit lines.

15. The information handling system as recited in claim 14 , wherein the touch controller further comprises a processing device coupled to the storage medium and configured to execute program instructions to compensate for the offsets in the digital sense signals stored within the first and second subsets of the rows in the memory table.

16. An information handling system, comprising:

a touch panel including a plurality of transmit lines and a plurality of receive lines arranged with the plurality of transmit lines in a grid pattern, such that a sense node is disposed on the touch panel at each intersection of the transmit and receive lines; and

a touch controller coupled to the touch panel for supplying drive signals to the plurality of transmit lines, receiving sense signals corresponding to the sense nodes from the plurality of receive lines, digitizing the received sense signals and storing the digital sense signals;

wherein the touch controller is configured to compensate for offsets in the digital sense signals corresponding to sense nodes associated with a first subset of the plurality of transmit lines and the digital sense signals corresponding to sense nodes associated with a second subset of the plurality of transmit lines;

wherein the first subset of the transmit lines are coupled to routing traces on only a first side of the touch panel, wherein the second subset of the transmit lines are coupled to routing traces on only a second side of the touch panel, and wherein a third subset of the transmit lines disposed between the first and second subsets of transmit lines are coupled to routing traces on both the first side and the second side of the touch panel; and

wherein the touch controller comprises:

a storage medium coupled to store the digital sense signals in a memory table having rows and columns, wherein:

a first subset of the rows comprises digital sense signals corresponding to the first subset of transmit lines,

a second subset of the rows comprises digital sense signals corresponding to the second subset of transmit lines, and

a third subset of the rows comprises digital sense signals corresponding to the third subset of transmit lines; and

a processing device coupled to the storage medium and configured to execute program instructions to compensate for the offsets in the digital sense signals stored within the first and second subsets of the rows in the memory table, and wherein the program instructions comprise:

a first set of program instructions executable to determine a first offset value by determining a difference between an average value of the digital sense signals stored within the first subset of rows and an average value of the digital sense signals stored within the third subset of rows, and

a second set of program instructions executable to determine a second offset value by determining a difference between an average value of the digital sense signals stored within the second subset of rows and the average value of the digital sense signals stored within the third subset of rows.

17. The information handling system as recited in claim 16 , wherein the program instructions further comprise a third set of program instructions executable to adjust the digital sense signals stored within the first and second subsets of rows in the memory table by:

applying the same first offset value to each of the digital sense signals stored within the first subset of rows; and

applying the same second offset value to each of the digital sense signals stored within the second subset of rows.

18. The information handling system as recited in claim 16 , wherein the processing device is further configured to execute program instructions to detect a location of a touch event on the touch panel based on the adjusted digital sense signals.

19. A method, comprising:

supplying drive signals to a plurality of transmit lines disposed on a touch panel;

receiving sense signals from a plurality of receive lines disposed on the touch panel;

digitizing the received sense signals and storing the digital sense signals in a memory table having rows and columns; and

adjusting the digital sense signals stored in the memory table by:

applying a first offset value to each of the digital signals stored within a first subset of the rows in the memory table; and

applying a second offset value to each of the digital signals stored within a second subset of the rows in the memory table, wherein the second offset value is different from the first offset value;

wherein the step of storing the digital sense signals in the memory table comprises:

storing digital sense signals corresponding to a first subset of the transmit lines, which are coupled to routing traces on only a first side of the touch panel, within the first subset of rows in the memory table,

storing digital sense signals corresponding to a second subset of the transmit lines, which are coupled to routing traces on only a second side of the touch panel, within the second subset of rows in the memory table, and

storing digital sense signals corresponding to a third subset of transmit lines, which are coupled to routing traces on both the first side and the second side of the touch panel, within a third subset of the rows in the memory table; and

wherein the step of adjusting the digital sense signals stored in the memory table further comprises:

determining the first offset value by determining a difference between an average value of the digital sense signals stored within the first subset of rows and an average value of the digital sense signals stored within the third subset of rows, and

determining the second offset value by determining a difference between an average value of the digital sense signals stored within the second subset of rows and an average value of the digital sense signals stored within the third subset of rows.