Alphanumeric LED Display HDSP2111
How to control the Alphanumeric LED Display HDSP2111
The HDSP2111 devices are 8-digit, 5 x 7 dot matrix, alphanumeric displays and are all packaged in a standard 15.24 mm (0.6 inch) 28 pin DIP.The onboard CMOS IC has the ability to decode 128 ASCII characters which are permanently stored in ROM. In addition, 16 programmable symbols may be stored in on-board ROM, allowing displaying user made symbols and icons. Seven brightness levels can adjust the display intensity and power consumption.The HDSP2111 is designed for standard microcontroller interface techniques. The display and special features are accessed through a bidirectional 8-bit data bus.
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Digital LED Thermometer
This project shows the temperature on a three digit 7-segment display, it measures the temperature from -9.5 to 99 degrees Celcius in 0.5 C steps, or from 0 to 210 degrees Fahrenheit in 1.0 degrees steps. Because of the LED display the temperature is also readable in the dark.
The TCN75 from MicroChip is used to measure the temperature. The TCN75 has a 2 wire serial interface, which is a bidirectional bus with a speed up to 400Kbs. Up to eight devices of the same type can be controlled by the bus. In this case only one device is connected to the ATTiny2313 microcontroller. The 2 wire bus is also called I2C, this name is proprietery to the Philips Electronics company. I2C is a abbreviation for IC Inter Circuit. The TCN75 has also a build in programmable thermostat, which is not used in this circuit.
This project is available pre-assambled and tested at www.bizztronix.net
The ATTiny2313 is used the control the two wire serial interfacing with the TCN75 and to translate the information for showing on the three digit 7-sement display. The reading of the temperature from the DS1621 happens every 3 seconds. A ceramic resonator is used for clocking the microcontroller.
The three 7-segment displays are of the common cathode type, at each cathode the display is connected to a transistor for ampifying the current. The transistors are of the NPN type and are controlled by the ATTiny2313 microcontroller. Each segment of the display is connected to a 200 Ohm resistor to limit the current of the ATTiny2313 port. The multiplexing of the three displays is handled in the software. Each display lights up consecutively for 5ms seconds. The LED digits have a height of 14,2mm (0.56").
The circuits needs a 5V DC regulated power supply and draws about 50mA current. It can also be supplied with three 1.5 volt batteries, but then the brightness of the LED's will be less. Three D-type batteries will last for about one month.
The program is written in the BASCOM-AVR programming language. The program uses about 1Kb of the 2Kb flash memory that the ATTiny2313 has. There are two different programs that you can use, for Celsius and for Fahrenheit read out. BASCOM is a programming language for AVR-microcontrollers based on BASIC, a demo version can be downloaded for free and can be used for up to 4Kb of programming code. BASCOM has special commands for driving chips with the two wire interface. Below you can download the program code and the hex files for the Celsius and the Fahrenheit mesurement. The BASCOM program compiles the program code into the hex-file that can then be loaded into the microcontroller to make the circuit work. BASCOM has also a build-in programmer to get the hex-file into the microcontroller. If you have the STK500 you can directly program the code from BASCOM into the microcontroller. Or you can use the parallel port program cable and the Attiny2313 board and the Pony-Prog program to get the code into the microcontroller.
You can buy the Attiny2313 board at www.bizztronix.net.
|Digital LED Thermometer_Celcius.bas|
|Digital LED Thermometer_Fahrenheit.bas|
Dot Matrix Scrolling Message
This is a Dot Matrix Scrolling Sign. A Dot Matrix Display has an 5x7 led matrix with 5 columns and 7 rows. The display is controlled by the AVR microcontroller. The rows are controlled by PORTB of the microcontroller, while PORTD puts the data on the columns to make the characters. The Dot matrix display used here is the LTR-747HR and is 0.7 inch (17.8mm) high.
The circuit is stand alone and can be connected to the ports B and D off the AVR microcontroller. The circuit consists of three shift registers IC's 74HC595 which switches each column of the displays sequentially on and off for 3ms. PORTB controls the the 74HC595. When a column is selected, the data for the column is put on PORTD, the signals from PORTB are amplified by the ULN2003, and switches the LED's on and off. While each column is swithed on and off seqeuntially, the characters on the display are formed. The PCB contains all the parts except for the microcontroller part. The PCB has to be connected via the two 10 pin flat cable connectors to the attinyboard or the STK500 for example. You can buy the ATTiny Board at www.bizztronix.net
The program code is made with the AVR-BASCOM compiler. There is a program for the ATTiny2313, which can show several moving messages on the sign.
There is also a program that is made for the ATMega8 which is more extensive, with this program you can enter a text with maximum 40 characters in a variable in the program, which is shown on the display. It has also a bigger character set.
|dot matrix display 4digit M8_1.bas|
|dot matrix display 4digit tiny2313_1.bas|
This running LED or LED chaser is a good project for beginners in the microcontroller technology. It is easy to build, and the assembler program code can be easily adapted. This running LED light has 15 red 3mm LED's. The 15 outputs of ports B and D are used to drive the leds.
The LED's light up in a pattern that can be made in the program code, the LEDs run back and forth.
With a push button you can select another pattern at which the LEDs runs. There are three running LED patterns which you can run: with one led, three leds and five leds.
There are also 4 patterns with fading LEDs:
- Fading out from the center to the side
- Fading out from the side to the center
- Fading out from left ot right
- Fading out from right to lef
If you can program in assembler you can extend the progam with more patterns. At the current program 300 bytes of the flash memory are used.
The project uses the ATTiny2313 micrcontroller but the ATTiny2313 can also be used.The AVR port can draw 20mA current so you only have to place a resitor at the port of the AVR to limit the current to 20mA. The LEDs are connected to ground so when the output of the port is high the LED will go on. The circuit uses a ceramic resonator of 10Mhz as oscillator. When you use ATTiny2313 you can discard the resonator because they have an on chip clock source. The fuse bits can be programmed to run the chip at 8Mhz.The circuit has to be powered with 5V DC regulated.
The program code is written in assembler. You can use AVR Studio to write the software, or you can use the parallel port program cable and IC-Prog to program the chip with the hex file.
Running LED Bicolor
This is a good project for beginners. It is easy to build.This running LED light uses seven bicolor led's red and yellow, they light up in a pattern that can be made within the program code.The program code is written in assembler. ATMELs AVR STUDIO is used to write the program.
The project uses the AT1200 but the AT2313 can also be used. As a clock source a 4Mhz ceramic resonator is used, this is cheaper than a crystal. The board has to be powered with 5V DC.
Because each I/O port of the AT2313 can draw 20mA current, each I/O port can drive a LED. The LED's are connected to the port B and port D of the AT2313. By connecting one end of the LED to port B and the other end of the LED the port D the polarity of the LED can be reversed. By putting a 1 on port B and a 0 on port D, the LED will go red. By putting a 0 on port B and a 1 on port D, the LED will go yellow. Now by writing sequently different bytes to the port B and port D, you can create different patterns in which the LED's will light up.
The software is written in assembler code and can be downloaded below.