Redundant sensing element sampling

• US 9,035,895 B2
• Filed: 03/13/2013
• Issued: 05/19/2015
• Est. Priority Date: 07/13/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Bussat, Jean-Marie, Hotelling, Steven P.
• Primary Examiner(s): Edun, Muhammad N
• Application Number:
  US13/802,609
• Publication Number:
  US 20140015774A1
• Time in Patent Office: 797 Days
• Field of Search: None
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06V 10/30 Noise filtering
• CPC Class Codes: G06V 40/1347 Preprocessing; Feature extraction

Abstract

A sensor system and method that adjusts sensor data to account for the presence of noise that causes variations in signal amplitude between sensor blocks and between sensor rows. In order to account for the presence of noise in a sensor apparatus, various embodiments apply a first adjustment to the sensor data to account for variations in signal amplitude that occur from block to block. Various embodiments may also apply a second adjustment to the sensor data to account for variations in signal amplitude that occur from row to row.

Claims

1. A method of compensating for the presence of noise in a touch sensing device, comprising

sampling a sensing element in a scan of a first data block to form a first value;

redundantly sampling the same sensing element in a scan of a different second data block to form a second value;

calculating an offset by subtracting the second value from the first value; and

adjusting the second data block by adding the offset to each data value of the second data block.

2. The method of claim 1, wherein

the first data block is offset from a fixed reference by a first amount;

prior to the operation of adjusting the second data block, the second data block is offset from the fixed reference by a second amount; and

following the operation of the adjusting the second data block;

the second data block is offset from the fixed reference by the first amount.

3. The method of claim 2, wherein the fixed reference is ground.

4. The method of claim 2, wherein the first and second data blocks correspond to first and second sensing element blocks of an array, the method further comprising

scanning a plurality of additional sensing element blocks in the array to form a plurality of additional data blocks;

adjusting the additional data blocks such that each additional data block is offset from the fixed reference by the first amount.

5. The method of claim 4, further comprising

storing the offset as a cumulative offset;

adding an additional offset to the cumulative offset for each scan of an additional data block, the additional offset being the difference between a sampled data value from a data block immediately prior to the additional data block and a redundantly sampled data value from the additional data block;

wherein for each additional data block, the operation of adjusting the additional data blocks includes adding the cumulative offset to each data value of the additional data block.

6. The method of claim 4, wherein

the plurality of additional sensing element blocks are members of a first row of sensing element blocks;

and

the first data block, the second data block, and the additional data blocks are members of a first row of data blocks, the method further comprising

scanning a second row of sensing element blocks to form a plurality of second row data blocks;

adjusting the second row of data blocks such that each data block in the second row is offset from the fixed reference by a third amount; and

adjusting the first and second rows of data blocks such that the first row of data blocks is offset from the fixed reference by an amount equal to an amount by which the second row of data blocks is offset from the fixed reference.

7. A method of compensating for the presence of noise in a touch sensing device, comprising

forming a data set by sequentially sampling an ordered array of sensing element blocks, the data set having rows of data blocks corresponding to rows of the ordered array;

applying a block-to-block adjustment to the data set based on redundant data values within the data set to form a partially compensated data set, wherein the redundant data values comprise data values that are sampled at least twice from redundant sensing elements in at least some of the sensing element blocks; and

applying a row-to-row adjustment to the partially compensated data set to form a compensated data set.

8. The method of claim 7, wherein each row of data blocks in the data set comprises an ordered set of data blocks beginning with a first block, the operation of applying the block-to-block adjustment further comprising, for each subsequent data block after the first data block in each row

calculating a block offset by subtracting a redundant data value of the subsequent data block from a redundant data value of a data block immediately prior to the subsequent data block;

calculating a cumulative offset as a sum of all the block offsets between the first data block and the subsequent data block;

adjusting the subsequent data block by adding the cumulative offset to each data value within the subsequent data block.

9. The method of claim 8, the operation of forming the data set further comprising, for each subsequent data block after the first block in each row

forming the redundant data value of the data block immediately prior to the subsequent data block by sampling a redundant sensing element a first time when a block of the array corresponding to the data block immediately prior to the subsequent data block is sampled, and

forming the redundant data value of the subsequent data block by sampling the redundant sensing element a second time when a block of the array corresponding to the subsequent data block is sampled.

10. A method of compensating for the presence of noise in a touch sensing device, comprising

sampling a first block of sensing elements to form a first sampled data block;

storing the sampled data block to form a first stored data block;

sampling a plurality of subsequent blocks of sensing elements to form a plurality of sampled subsequent data blocks;

for each of the sampled subsequent data blocks;

adding a stored cumulative offset to the sampled subsequent data block to form an adjusted subsequent data block; and

storing the adjusted subsequent data block to form a stored subsequent data block.

11. The method of claim 10, further comprising

storing a redundant data value of the first sampled data block as the stored cumulative offset;

and

for each of the sampled subsequent data blocks and prior to the operation of adding the stored cumulative offset to the sampled subsequent data block;

adding the stored cumulative offset to a redundant data value of the sampled subsequent data block to form an adjusted cumulative offset;

storing the adjusted cumulative offset as the stored cumulative offset.

12. The method of claim 11, wherein

the redundant data value of each sampled subsequent data block is associated with a redundant sampling element;

the redundant sampling element being sampled a first time when the data block immediately prior to the subsequent data block is sampled; and

the redundant sampling element being sampled a second time when the subsequent data block is sampled.

13. A sensor apparatus, comprising

an array of sensing element arranged in rows of sensing element blocks, the array including a plurality of redundant sensing elements, each individual one of the redundant sensing elements contained within two adjacent sensing element blocks;

a block address input configured to receive input that specifies an individual one of the sensing element blocks; and

a read channel output configured to output data from the individual one of the sensing element blocks responsive to the input received at the block address input.

14. The sensor apparatus of claim 13, further comprising

a sampling block connected to the read channel output from the sensor array, the sampling block configured to sample the read channel of the array and to provide the sampled data on corresponding output lines.

15. The sensor apparatus of claim 14, further comprising

a multiplexor connected to the output lines of the sampling block, the multiplexor configured to convey output from one of the output lines of sampling block to a multiplexor output responsive to a channel selector input.

16. The sensor apparatus of claim 15, further comprising

an analog-to-digital converter connected to the output of the multiplexor;

and

a memory connected to the output of the analog-to-digital converter.

17. The sensor apparatus of claim 16, further comprising a processor connected to the memory, wherein

the memory contains a data set of sequentially sampled sensing element blocks, the data set having rows of data blocks corresponding to rows of the array;

the processor configured to apply a block-to-block adjustment to the data set based on redundant data values within the data set to form a partially compensated data set; and

the processor configured to apply a row-to-row adjustment to the partially compensated data set to form a compensated data set.

18. The sensor apparatus of claim 16, further comprising

a first register connected to the output of the analog-to-digital converter, the first register configured to store a digital value for a redundant sensing element as sampled in an immediately prior block scan;

a second register connected to the output of the analog-to-digital converter, the second register configured to store a digital value for the redundant sensing element as sampled in a current block scan;

a first adder having a first input connected to the output of the first register and a second input connected to the output of the second register, the first adder configured to provide an output representing the difference between the value output by the first register and the value output by the second register; and

a second adder having a first input connected to the output of the first adder, a second input connected to the output of the analog-to-digital converter, the second adder configured to provide an output representing the difference between the value output by the analog-to-digital converter and the value output by the first adder;

the output of the second adder connected to the memory.

19. The sensor apparatus of claim 16, further comprising

a data store connected to an output of the sampling block;

a first adder having a first input connected to the output of the data store, a second input connected to an output of the sampling block, and an output; and

a second adder having a first input connected to the output of the multiplexor, a second input connected to the output of the first adder, and an output connected to the analog-to-digital converter.

20. The sensor apparatus of claim 13, wherein the block address input further comprises

a first column row enable that enables only the first sensing element of the first sensing element block of a particular row;

and

a common row enable configured to enable all of the sensing elements except the first sensing element in a sensing element block if the first sensing element block is specified, and configured to enable all of the sensing elements in a sensing element block if the first sensing element block is not specified.