Cypress PSoC Style AN2034 user manual

Summary of the content on the page No. 1

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User Interface - Keypad Scan, PSoC Style

AN2034
Author: Dave Van Ess
Associated Project: Yes
Associated Part Family: CY8C20x34, CY8C21x23, CY8C21x34
CY8C23x33, CY8C24x23A, CY8C24x94
CY8C27x43, CY8C29x66
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Software Version: PSoC Designer™ 5.0
Associated Application Notes: AN2354
Application Note Abstract
X–Y matrix keypads are an inexpensive interface enabling interaction with microcontroller-based products. This application
note shows how the PSoC® microcontro

Summary of the content on the page No. 2

AN2034 Figure 4 shows implementation of a keypad scan. PSOC General Purpose IO Figure 4. PSoC Architecture for Keypad Scan To detect single-switch closures, use the following algorithm: C C C C 0 1 2 3 P X.0 Drive all rows simultaneously and read the columns. R 0 P Drive all columns simultaneously and read the rows. X.1 R 1 Condense this data to determine switch-closure P X.2 R status. 2 The structure of the general purpose of each pin simplifies P X.3 R 3 this bipolar use of rows a

Summary of the content on the page No. 3

AN2034 Code 1: Subroutine for Reading Keypad Using the Output ;----------------------------------------- The output of the function bReadKeypad is a single byte ; Keypad.asm that shows the status of key closure of the keypad. It is ; translated and decoded as follows: ; This routine reads a 4 column by 4 row ; keypad on port1. The status of key No bits are set if no key is pressed. ; closures is returned in A. ; A single bit in the upper nibble and a single bit in the ;

Summary of the content on the page No. 4

AN2034 Example Code 3 is the main function that implements the Debouncing design in Figure 5 on page 3. Debouncing solutions are specific to each system’s Code 3. Keypad Project Implemented program structure and switch selection. However, debouncing is simple; it requires two sequential keypad ;----------------------------------------- scans to agree for the scan to be valid. ; This program reads the keypad ; at port 1 and control the LEDs ; on port0. Interrupt Driven Keypad Scans

Summary of the content on the page No. 5

AN2034 Document History ® Document Title: User Interface – Keypad Scan, PSoC Style Document Number: 001-40409 Revision ECN Orig. of Submission Description of Change Change Date ** 1532004 OGNE 10/02/07 New publication of existing application note. *A 2640952 JVY 01/20/09 Updated content. Added part numbers CY8C20x34, CY8C21x23, CY8C21x34, CY8C23x33, CY8C24x23A, CY8C24x94, CY8C27x43, and CY8C29x66. In March of 2007, Cypress recataloged all of its Application Not