Embedded Systems Design with the Atmel AVR Microcontroller Part II

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204 CHAPTER 7. ATMEL AVR OPERATING PARAMETERS AND INTERFACING character, multi-line display. A larger display does not require a significant number of microcontroller pins for the interface. The dot matrix display may be used to display alphanumeric data as well as graphics data. In Figure 7.11b), we have provided additional detail of the interface circuit. 7.4.6 LIQUID CRYSTAL CHARACTER DISPLAY (LCD) An LCD is an output device to display text information as shown in Figure 7.12. LCDs come in a wide variety of configurations, including multi-character and multi-line format. A 16times2 LCD format is common. That is, it has the capability of displaying two lines of 16 characters each. The characters are sent to the LCD via American Standard Code for Information Interchange (ASCII) format a single character at a time. For a parallel configured LCD, an eight bit data path and two lines are required between the microcontroller and the LCD. A small microcontroller mounted to the back panel of the LCD translates the ASCII data characters and control signals to properly display the characters. LCDs are configured for either parallel or serial data transmission format. In the example provided we use a parallel configured display. In Figure 7.13, we have included the LCD in the Testbench hardware configuration. Figure 7.12: LCD display. AND671GST line1 line2 GND-1 VDD-2 Vo-3 RS-4 R/W-5 E-6 DB0-7 DB1-8 DB2-9 DB3-10 DB4-11 DB5-12 DB6-13 DB7-14 10K Vcc command/data enable data Some sample C code is provided below to send data and control signals to an LCD. In this specific example, an AND671GST 1 × 16 character LCD was connected to the Atmel ATmega164 microcontroller.One 8-bit port and two extra control lines are required to connect the microcontroller to the LCD. Note: The initialization sequence for the LCD is specified within the manufacturer’s technical data. //************************************************************************* //LCD_Init: initialization for an LCD connected in the following manner: //LCD: AND671GST 1x16 character display //LCD configured as two 8 character lines in a 1x16 array
47 G V DD = 5 VDC R 74HC14 47 G 4.7K R 470K SW0 47 G 0.1 uF R ATmega16 47 G R 1-(TO) PB0 2-(T1) PB1 3-(AIN0) PB2 4-(AIN1) PB3 5-(SS) PB4 47 G R 47 G VDD R 47 G R 47 G PA0 (ADC0)-40 PA1 (ADC1)-39 PA2 (ADC2)-38 PA3 (ADC3)-37 PA4 (ADC4)-36 PA5 (ADC5)-35 PA6 (ADC6)-34 PA7 (ADC7)-33 AREF-32 AGND-31 AVCC-30 PC7 (TOSC2)-29 PC6 (TOSC1)-28 PC5-27 PC4-26 PC3-25 PC2-24 PC1-23 PC0-22 PD7 (OC2)-21 PORTA PORTB 6-(MOSI) PB5 7-(MISO) PB6 8-(SCK) PB7 9-RESET 10-Vcc 11-GND 12-XTAL2 13-XTAL1 14-(RXD) PD0 15-(TXD) PD1 16-(INT0) PD2 17-(INT1) PD3 18-(OC1B) PD4 19-(OC1A) PD5 20-(ICP) PD6 Figure 7.13: Hardware Testbench equipped with an LCD. V DD = 5 VDC 74HC14 4.7K sys reset 1M VDD 1.0 uF 470K SW7 0.1 uF PORTD PORTC 8 R enable ZTT 10MHz resonator 7.4. OUTPUT DEVICES 205 command/data Vcc Vcc data 2N2222 - + LM324 2N2907 Vcc 10K 3.0 K 8 GND-1 VDD-2 Vo-3 RS-4 R/W-5 E-6 DB0-7 DB1-8 DB2-9 DB3-10 DB4-11 DB5-12 DB6-13 DB7-14 3.0 K AND671GST line1 line2
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Embedded Systems Design with the At
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iv An Introduction to Logic Circuit
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Copyright © 2010 by Morgan & Clayp
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ABSTRACT This textbook provides pra
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x CONTENTS 7 6.9.3 Input Capture Mo
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xii CONTENTS A 8.5.3 Circuit diagra
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Preface In 2006 Morgan & Claypool P
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270 APPENDIX A. ATMEGA164 REGISTER
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272 APPENDIX A. ATMEGA164 REGISTER
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274 APPENDIX B. ATMEGA164 HEADER FI
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Author’s Biography STEVEN F. BARR
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296 INDEX switch debouncing, 187 sw
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