Graphic Editor: Analog Keyboard Encoder
This design example allows you to decode a large number of switches in a keypad or keyboard with only two I/O pins and a GND pin using Altera® MAX® II devices.
The circuit in Figure 1 shows how an Altera EPM570-T100 (along with an external capacitor) can utilize its internal oscillator, Schmitt trigger I/O, and high-density arithmetic programmable logic fabric to replace an A/D converter to decode an analog switch array.
Download the analog keyboard encoder graphic editor files.
Figure 1. Block Diagram for Two Wire Keypad Decode Using MAX II Devices

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For more information on using this example in your project, go to:
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