Touch Screen Controller Filtering for LCD Switching Noise
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Solution Overview
Problem
Existing touch screen systems face challenges in reducing noise, particularly from LCD switching, which affects the accuracy of touch point coordinate measurements, and current solutions are costly or burdensome in terms of additional hardware and software requirements.
Innovation Solution
A touch screen controller circuitry that employs a median filter and a mean filter in conjunction, utilizing state machines to sort and average digital data numbers, effectively reducing noise by shifting and processing data to isolate and eliminate noise spikes and Gaussian noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LCD switching is used to indicate touch screen activation, then power saving is achieved, but noise is generated that corrupts touch point coordinate data
Solution Approach 1:
The patent detects the LCD switching noise and converts this harmful interference into useful information by using the noise detection signal to identify and exclude corrupted data samples from the averaging process, thereby maintaining power saving operation while eliminating the harmful effect of the noise on measurement accuracy
Solution Approach 2:
The patent introduces an intermediary noise detection mechanism that monitors LCD switching events and uses this intermediate information to control the data processing workflow, allowing the system to identify when noise is present and adjust its averaging operation accordingly without requiring additional hardware beyond the controller
2Measurement precision
If conventional noise filtering methods are used, then noise reduction is achieved, but additional costly hardware or complex software synchronization is required
Solution Approach 1:
The touch screen controller performs self-service by using its own existing resources (CPU, memory, and standard filtering algorithms) to detect and eliminate noise without requiring external hardware assistance or complex synchronization protocols with the host processor, thereby achieving noise reduction while maintaining simplicity
Solution Approach 2:
The patent dynamically changes the parameter of data sample selection by using a flag bit to indicate whether the current sample should be included in averaging based on detected noise conditions, allowing the system to adapt to varying noise environments using simple parameter changes rather than complex hardware or software modifications
Data Source
AI summary
A touch screen system includes a touch screen assembly (30,31) and a touch screen controller (1A) coupled to terminals (24,25,26,27) of the touch screen assembly (30,31), the touch screen controller (1A) including a controller (41) and an analog to digital converter (22) for generating multiple digital data numbers representing multiple coordinate values, respectively, of a particular touch point (Q) of the touch screen assembly (30,31) in response to control signals (42) generated by the controller (41). A sorting technique is performed to sort the digital data numbers in order of their values, respectively. An averaging technique is performed on at least some of the sorted digital data numbers, including a median sorted digital number.