read barcode from image c#.net INTERFACING LED DISPLAYS 133 in Software

Generator Code 128 Code Set B in Software INTERFACING LED DISPLAYS 133

INTERFACING LED DISPLAYS 133
Code128 Reader In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
Code 128 Drawer In None
Using Barcode creation for Software Control to generate, create Code 128A image in Software applications.
Host
Code-128 Recognizer In None
Using Barcode decoder for Software Control to read, scan read, scan image in Software applications.
USS Code 128 Creator In C#.NET
Using Barcode encoder for .NET framework Control to generate, create Code 128 Code Set B image in .NET framework applications.
MAX521 #1
Code 128A Generation In .NET
Using Barcode drawer for ASP.NET Control to generate, create Code 128C image in ASP.NET applications.
Code-128 Printer In VS .NET
Using Barcode drawer for VS .NET Control to generate, create Code128 image in VS .NET applications.
MAX521 #2
Paint Code 128 Code Set B In Visual Basic .NET
Using Barcode encoder for VS .NET Control to generate, create Code 128 Code Set C image in VS .NET applications.
Code39 Generator In None
Using Barcode generation for Software Control to generate, create Code 39 image in Software applications.
+5 V
Barcode Drawer In None
Using Barcode creator for Software Control to generate, create bar code image in Software applications.
EAN 128 Creation In None
Using Barcode creator for Software Control to generate, create UCC-128 image in Software applications.
MAX521 #3
Create UPC-A In None
Using Barcode maker for Software Control to generate, create UPC-A Supplement 5 image in Software applications.
Generate Barcode In None
Using Barcode generation for Software Control to generate, create bar code image in Software applications.
+5 V
4-State Customer Barcode Printer In None
Using Barcode generation for Software Control to generate, create Intelligent Mail image in Software applications.
EAN 13 Drawer In None
Using Barcode generator for Online Control to generate, create EAN-13 image in Online applications.
MAX521 #4
Making Code 128C In Java
Using Barcode maker for Java Control to generate, create Code 128A image in Java applications.
Bar Code Drawer In .NET
Using Barcode printer for ASP.NET Control to generate, create barcode image in ASP.NET applications.
+5 V
Making Barcode In Java
Using Barcode creation for Android Control to generate, create barcode image in Android applications.
Linear 1D Barcode Encoder In Java
Using Barcode generator for Java Control to generate, create 1D image in Java applications.
+5 V
Draw Data Matrix ECC200 In Java
Using Barcode drawer for Java Control to generate, create Data Matrix image in Java applications.
GTIN - 13 Generator In Java
Using Barcode drawer for Java Control to generate, create EAN 13 image in Java applications.
Figure 6.28 Connecting multiple MAX521s on a single bus.
DOT MATRIX DISPLAYS
Dot matrix displays are the best in terms of the type of information that can be displayed, including graphics. Dot matrix displays are necessarily multiplexed displays. Figure 6.33 illustrates an interface circuit for a 5-by-7 dot matrix display. Figure 6.34 is a circuit diagram for a AT90S2313 controlled dot matrix display. The display is arranged as five columns of seven LEDs each. Each column is refreshed at a rate of 40 Hz at 4.00-MHz
134 HARDWARE AND SOFTWARE INTERFACING WITH THE AVR
MAX521 DAC0 +5V AT90S2313 .1 uF Vcc(20) PB5(17) SDA DAC1 DAC2 DAC3 DAC4 RESET(1) .1 uF X2(4) X1(5) 4 MHz 22 pF 22 pF Gnd(10) AD0 AD1 DAC6 DAC7 PB4(16) SCL DAC5
Figure 6.29 Connecting AT90S2313 AVR processor to MAX521 DAC.
AVR Processor R
PORTB
PORTD
Figure 6.30 Seven-segment LED display interface to the AVR processor.
INTERFACING LCD DISPLAYS 135
+5V AVR Processor Rb Ra
PORTB
R1 a b c d e f g
Figure 6.31 A multiplexed seven-segment LED display interface to the AVR processor.
PORTD
Figure 6.32 An alphanumeric LED display.
clock frequency. The actual clock frequency used for the circuit is 3.58 MHz and so the refresh rate is about 36 Hz. This is an illustrative circuit. The code just waits for a key to be pressed, and at each key press it displays a new number or a new alphabet in a sequence. Since there are five columns of LEDs, the duty cycle of current flowing in each column is 20%, and so to maintain the same average current (of 4 mA) the peak current is increased five times to 20 mA. The value of the current-limiting resistor is hence chosen to be 150 ohms. Figure 6.35 illustrates the test board for the 5 7 dot matrix display. Code for this circuit is available in the code directory in the file 5x7disp.asm.
6.10 Interfacing LCD Displays
LCD displays are very useful for displaying user information and communication. LCD displays are available in various formats. Most common are 1x16, i.e., 1 line with 16 alphanumeric characters. Other formats are 2x16, 1x40, 2x40, 4x16, etc. The LCD displays have the following format:
136 HARDWARE AND SOFTWARE INTERFACING WITH THE AVR
AVR Processor
Column PortB Driver (Current source) (Anodes)
PortD
(Cathodes) 5 x 7 Dot Matrix Display
Figure 6.33 Block diagram for a 5-x-7 dot matrix display to AVR interface.
SYMBOL
FUNCTION
1 2 3 4
Vss Vcc Vdd RS
Power supply Gnd Power supply Contrast adjust 0 1 Instruction input Data input Write to LCD Read from LCD 5V
6 7 8 9 10 11
E DB0 DB1 DB2 DB3 DB4
Enable signal
I/O Data bit line 0 (LSB) I/O Data bit line 1 I/O Data bit line 2 I/O Data bit line 3 I/O Data bit line 4
INTERFACING LCD DISPLAYS 137
12 13 14
DB5 DB6 DB7
I/O Data bit line 5 I/O Data bit line 6 I/O Data bit line 7 (MSB)
Figure 6.34 Circuit schematic for a 5-x-7 dot matrix display interface.
138 HARDWARE AND SOFTWARE INTERFACING WITH THE AVR
Figure 6.35 A 5-x-7 dot matrix display test board photograph.
The LCD modules have an 8-bit interface. Besides the 8-bit data bus, the interface has a few other control lines. The default data transfer between the LCD module and an external device is 8 bits, however it is possible to communicate with the LCD module using only four of the eight data lines. Figure 6.36 illustrates the character codes for the LCD, and Figure 6.37 shows how to interface a 2-x-16 line LCD module to an AT90S2313 processor. The R/W line is connected to ground and hence the processor cannot read any status information from the LCD module, but can only write data to the LCD. The source code for the LCD interface example is available on the CD in the code directory in the file my_lcd.asm.
6.11 Driving Relays with AVR
The ULN2003A are high-voltage, high-current darlington arrays containing seven open collector darlington pairs with common emitters. Each of the seven channels can handle 500 mA of sustained current with peaks of 600 mA. Each of the channels has a suppression diode that can be used while driving inductive loads (such as relays) as freewheeling diodes. The ULN2003A input is TTL compatible. Typical uses of these drivers include driving solenoids, relays, DC motors, LED displays, thermal print heads, etc. The IC is available in a 16-pin DIP package and other packages. The outputs of the drivers can also be paralleled for higher currents, though this may require a suitable loadsharing mechanism. Figure 6.38 shows the block diagram of the ULN2003A darlington array driver IC. For each of the drivers, there is a diode with the anode connected to the output and the cathode connected to a common point for all the seven diodes. The outputs are open-collector, which means that external load is connected between the power supply and the output of the driver. The power supply can be any positive voltage less than 50 V as specified by the data sheets. The load value should be such that it needs sustained currents less than 500 mA and peak currents less than 600 mA per driver.
Copyright © OnBarcode.com . All rights reserved.