Time-Division I/O Multiplexing for LED and Switch Control
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Solution Overview
Problem
Conventional electric devices with LED lamps and switches require dedicated logic circuits and signal lines for high-speed switching, leading to increased manufacturing costs and inadequate LED brightness control, which limits uniformity and gradation of light emission.
Innovation Solution
An electric device using general-purpose input/output ports to time-divisionally control light emitting elements and switch detection, eliminating the need for dedicated logic circuits and allowing for fine light emission control without dedicated signal lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated logic circuits and signal lines are used for high-speed switching control, then LED light emission control and switch input detection control can be performed independently, but the circuit scale increases and manufacturing cost rises
Solution Approach 1:
The patent merges the control of multiple LEDs and detection of multiple switches into a single general-purpose I/O port through time-divisional multiplexing. The microcomputer alternates between outputting driving signals to LEDs and inputting switch press detection signals using the same port, eliminating the need for separate dedicated logic circuits and signal lines for each LED and switch, thus reducing circuit scale while maintaining independent control capability
Solution Approach 2:
The general-purpose I/O port is designed to perform multiple functions: it can output driving signals to control LED light emission and simultaneously function as an input port to detect switch press operations. This multi-functional design replaces multiple dedicated ports, reducing the overall circuit complexity while preserving the ability to independently control LEDs and detect switch inputs
2Device complexity
If time-divisional driving is used to control multiple LEDs, then circuit complexity is reduced, but light emission control time is insufficient and LED brightness uniformity deteriorates
Solution Approach 1:
The patent implements periodic time-divisional control where the microcomputer systematically cycles through each LED in sequence, outputting driving signals to each LED for a predetermined period. This periodic action ensures that each LED receives adequate illumination time within each control cycle, maintaining uniform brightness across all LEDs while keeping the circuit simple through shared I/O port usage
Solution Approach 2:
The control program pre-establishes the time-divisional control sequence and allocation for each LED before execution. By preliminarily determining the driving signal output timing and duration for each LED, the system ensures that each LED receives sufficient light emission time, thereby maintaining brightness uniformity while using a simplified circuit configuration
3Ease of manufacture
If simple time-divisional control is used, then manufacturing cost is reduced, but fine light emission control and brightness gradation capability are lost
Solution Approach 1:
The patent implements dynamic control within the time-divisional framework by allowing flexible adjustment of the driving signal output duration for each LED. The microcomputer can dynamically modify the light emission time of individual LEDs based on operational requirements, enabling brightness gradation and fine control while still using a single general-purpose I/O port, thus maintaining low manufacturing cost while achieving precise control
Data Source
AI summary
An embodiment of this invention relates to an electric device capable of controlling a plurality of elements with an inexpensive, simple configuration, and a printing apparatus using the same. In this embodiment, an operation unit of the printing apparatus switches the states of a plurality of general purpose input/output ports between low-level signal output, high-level signal output, and input high impedance for each time set in a timer by an MPU. This allows LED light emission control and switch key press detection. Also, output ports used for LED light emission control, and input ports used for key press detection are shared using general purpose input/output ports to realize LED light emission control and switch key press detection with a configuration simpler than the conventional configuration.