Virtual Keypad Interface Using SerDes to Cut Hinge Flex Wires
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Solution Overview
Problem
Existing keypad interfaces in mobile devices require numerous parallel wires across the hinge flex cable, which reduces reliability as the number of keys increases and device size decreases, necessitating a more efficient use of wires.
Innovation Solution
A serializer/deserializer system is implemented to convert parallel scan and sense signals into a serial data stream, reducing the number of wires needed across the flex cable by using only two wires for a clock signal and serial data, allowing the microprocessor to logically receive signals as if directly connected to the keypad.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parallel wires are used to connect the microprocessor directly to the keypad, then the connection is simple and direct, but the number of wires increases as the number of keys increases, reducing reliability
Solution Approach 1:
The patent segments the parallel keypad interface into two separate functions: a serializer that converts parallel scan/sense signals to serial data, and a deserializer that converts serial data back to parallel signals at the microprocessor. This segmentation allows the physical wire count to be reduced while maintaining the logical keypad interface functionality.
Solution Approach 2:
The patent introduces intermediary devices (serializer and deserializer) between the keypad and the microprocessor. The serializer acts as a mediator that translates the parallel keypad signals into a compact serial format for transmission over the flex cable, and the deserializer mediates the reverse translation at the other end, thereby reducing wire count without losing functionality.
2Adaptability or versatility
If the number of keys increases to provide more functionality, then the device becomes more versatile, but the number of parallel wires required increases, making the device larger and less reliable
Solution Approach 1:
The patent transitions from a two-dimensional parallel wire layout to a one-dimensional serial data stream. By encoding multiple keypad signals into a single serial data line transmitted over time rather than space, the solution reduces the physical dimension (wire count) required while maintaining the ability to handle increased numbers of keys for greater versatility.
3Quantity of substance
If more wires are used in the flex cable to support more keys, then more keys can be connected, but the cable becomes larger and reliability decreases
Solution Approach 1:
The patent merges multiple parallel signal lines (scan lines and sense lines) into a single serial data line for transmission across the flex cable. By combining the information from multiple wires into one serial stream through the serializer, the solution reduces the quantity of physical wires needed while still supporting a large number of keys, thereby improving reliability.
Data Source
AI summary
A serializer/deserializer interfacing a keypad or keyboard to a processing system is illustrated. However, to minimize wires on intervening cables, a serializer and deserializer is inserted between the processor system and the keypad forming a virtual keypad. The processor scans the deserializer as if it were the keypad and the keypad is scanned by the serializer as if it were the processor. The serializer converts the scanning of the keypad into a serial bit stream and clock that is sent to the deserializer. The deserializer accepts the serial bit stream and reconfigures the data into a response that mimics the response of the physical keypad. In one embodiment an actual second keypad is formed in the deserializer and activated as the first keypad is activated.