Touchscreen Readout Circuitry Noise Filtering via Sample Subsets
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Solution Overview
Problem
Cellular devices with touchscreens face challenges in accurately deciphering touch inputs due to electrical grounding variations and noise from external sources, which complicates the interpretation of touch signals, especially during charging or power-up, and can lead to misinterpretation of noise as actual input.
Innovation Solution
The electronic device employs a touchscreen with a plurality of sensing capacitors and readout circuitry that accumulates samples, divides them into subsets, removes noisy subsets based on a threshold, and processes remaining subsets for touch input, using a drive circuit with a clock signal, an amplifier, accumulator circuit, and analog-to-digital converter to provide accurate digital output values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the device includes a touchscreen input to provide a larger display, then the display area is increased, but the device becomes more susceptible to electrical noise and grounding variations that complicate touch input detection
Solution Approach 1:
The sample set from each sensing capacitor is divided into multiple sample subsets, allowing the system to process and evaluate individual subsets separately. This segmentation enables identification and removal of noisy subsets while retaining valid touch data from other subsets, thereby maintaining touch detection accuracy despite the presence of electrical noise and grounding variations.
Solution Approach 2:
The system dynamically adjusts the threshold parameter for noise rejection based on statistical analysis of sample subsets. By changing the threshold parameter adaptively, the system can distinguish between actual touch inputs and electrical noise under varying grounding conditions, maintaining reliable touch detection across different electrical environments.
2Speed
If the readout circuitry processes all sample data without filtering, then processing speed is maintained, but noise from external sources may be misinterpreted as actual touch input
Solution Approach 1:
The readout circuitry performs preliminary filtering of sample subsets before final processing by identifying and removing noisy subsets based on threshold comparisons. This preliminary action eliminates invalid data early in the processing pipeline, ensuring that only reliable touch data proceeds to further processing, thereby maintaining both speed and accuracy.
Solution Approach 2:
The system uses its own accumulated sample data to establish thresholds for noise rejection. By leveraging the statistical properties of its own sample sets, the readout circuitry autonomously determines appropriate filtering criteria without requiring external calibration or intervention, enabling real-time adaptive noise rejection.
3Measurement precision
If the device removes noisy sample subsets through threshold-based filtering, then touch input accuracy is improved, but additional processing steps increase circuit complexity
Solution Approach 1:
The sampling process is segmented into multiple subsets that can be independently evaluated against a threshold. This segmentation allows the use of simple comparative operations for each subset rather than complex continuous filtering, achieving high measurement precision through repeated simple decisions rather than a single complex processing step.
Solution Approach 2:
The threshold parameter is dynamically adjusted based on the statistical characteristics of the accumulated samples. By changing the threshold parameter adaptively rather than using fixed complex filtering algorithms, the system achieves high touch input detection accuracy with relatively simple circuit implementation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the accuracy of touch input detection by filtering out noise and maintaining sensitivity, allowing the processor to differentiate between actual touch and noisy states, thereby improving the reliability of touch input recognition.
Implementation Method 1
a touchscreen comprising a plurality of sensing capacitors
Implementation Method 2
an amplifier coupled downstream of each sensing capacitor
Implementation Method 3
an accumulator circuit coupled downstream from the amplifier
Implementation Method 4
an analog-to-digital converter (ADC) coupled downstream from the accumulator circuit
Data Source
AI summary
An electronic device may include a touchscreen having sensing capacitors, and readout circuitry. The readout circuitry may be configured to accumulate a sample set from each sensing capacitor, divide the sample set into sample subsets, remove a given sample subset when the given sample subset exceeds a threshold, and process remaining sample subsets for touch input.