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PIC in Practice, 2nd Edition by David W Smith

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7

Keypad scanning

There are no new instructions used in this chapter

Keypads are an excellent way of entering data into the microcontroller. The keys are usually numbered but they could be labeled as function keys for example in a remote control handset in a TV to adjust the sound or colour etc.

As well as remote controls, keypads find applications in burglar alarms, door entry systems, calculators, microwave ovens etc. So there are no shortage of applications for this section.

Keypads are usually arranged in a matrix format to reduce the number of I/O connections.

A 12 key keypad is arranged in a 3 × 4 format requiring 7 connections.

A 16 key keypad is arranged in a 4 × 4 format requiring 8 connections.

Consider the 12 key keypad. This is arranged ...

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