Touch Screen Controller FIFO Buffering for Interrupt Reduction
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Solution Overview
Problem
Existing touch screen systems generate a high number of interrupts, leading to resource wastage and potential data loss when the processor is busy, as they require overhead processes and may ignore interrupts, causing missed data points.
Innovation Solution
Integration of FIFO memory and a timer in the touch screen system to reduce interrupts by automatically acquiring data during touch detection and issuing interrupts only when a FIFO threshold is reached or the timer expires, ensuring no data is missed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the touch screen controller issues an interrupt for every data acquisition, then the host can read the data in a timely manner, but the number of interrupts increases, wasting processor resources and potentially causing data loss when the processor is busy
Solution Approach 1:
The controller preliminarily acquires touch data and stores it in the FIFO buffer before the host is ready to read. This preliminary action allows the controller to prepare data in advance without requiring immediate host intervention, reducing the frequency of interrupts while ensuring data is available when the host becomes available.
Solution Approach 2:
The FIFO buffer acts as an intermediary between the data acquisition block and the host. It decouples the data acquisition process from the host reading process, allowing the controller to accumulate multiple data points before triggering an interrupt, thus reducing interrupt frequency while maintaining data completeness.
2Productivity
If the processor ignores interrupts when handling higher priority processes, then critical tasks are completed, but touch data points are lost since the controller waits for commands
Solution Approach 1:
The controller preliminarily acquires and stores touch data in the FIFO buffer before the host needs to read it. This ensures that even if the host is busy with higher priority tasks and delays interrupt handling, the data is already captured and stored, preventing any data loss.
Solution Approach 2:
The data acquisition block operates autonomously, continuously acquiring touch data and storing it in the FIFO buffer without requiring host intervention for each data point. This self-service mechanism ensures data acquisition continues uninterrupted regardless of host processor availability.
3Reliability
If the controller automatically acquires data when touch is detected without host intervention, then data acquisition continues without missing points, but the host cannot read data in real-time
Solution Approach 1:
The FIFO buffer serves as an intermediary that temporarily holds acquired data, allowing the controller to continue acquiring data autonomously while the host reads data at its own pace. This decoupling ensures data acquisition continuity without forcing real-time reading, and the host can process data as soon as it becomes available.
Solution Approach 2:
The controller performs preliminary data acquisition and storage in the FIFO buffer, preparing data in advance for host reading. This preliminary action ensures data is ready when the host is available, eliminating both data loss and unnecessary delays in data processing.
Data Source
AI summary
Integration of a FIFO memory, FIFO threshold and a timer, along with the other components of a touch screen system allows the number of interrupts to the touch screen controller to be reduced while allowing all point data to be acquired and preserved. In the first touch-detect event, an interrupt is issued to inform the host. The touch screen controller then automatically acquires data as long as touch is detected without host intervention. A FIFO threshold defines the minimum number of data points in FIFO memory before it issues an interrupt to inform the host that data is ready to be fetched. The timer is started once touch is detected. On every single data acquired, the timer is reset. In the event where touch is no longer detected, the timer keeps on counting until the time-up limit is reached. In this event, the touch screen controller will issue an interrupt informing the host the pen is lifted. The host then checks whether there is still data left in FIFO memory to be read.