5digital_IO-atmel - Digital I/O Laboratory DIO-1 Digital...

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Digital I/O Laboratory DIO-1 © San José State University Dept. of Mechanical and Aerospace Engineering rev. 3.01 25FEB07 Digital Signal Input and Output Purpose: To introduce the digital input and output functions of the ATmega128 microcontroller. To practice reading logic level signals from an input port. To practice sending logic level signals to an output port. Components: Qty. Item 1 Atmel ATmega128 microcontroller, STK500 and STK501 interface boards, and serial port cable. 1 Solderless Breadboard 2 470 Ω DIP resistor pack 1 7-segment LED (common anode (CA)) 2 7447 BCD to 7-segment LED decoder IC Introduction: In this lab you will explore the input/output capability of the ATmega128 microcontroller. Microcontrollers are inherently digital devices, which means they operate with discrete values, usually the binary values 0 and 1 corresponding to the voltages 0 V and 5 V respectively. The discrete value of 0V is considered a “Low” or a 0 and that of 5V is considered a “High” or a 1. The ATmega 128 microcontroller can service up to 53 digital inputs or outputs . A digital output means that a program running on the ATmega 128 can change the pin voltage to be either at common potential (0V) or at 5 V by writing a 0 or 1 to that pin. A digital input means that the world outside the microcontroller can change the voltage on the pin to either 0 V or 5 V, and the microcontroller can record the value as a 0 or 1 respectively. 7-segment LED display You will use a 7-segment light emitting diode (LED) display as a digital output device and push-button switches as digital input devices. A 7-segment LED is nothing more than 7 LED’s arranged in a pattern that can form a character when the appropriate segments are lit. These displays come in two basic types: common anode (CA) and common cathode (CC). CA types have all of the anodes of the 7 LED’s connected together, and each of the 7 cathodes independent. Power is applied to the common anode, and a segment will be lit when its cathode is grounded. (Don’t forget to use a current limiting resistor between the cathode and ground!) The reverse is true for the CC types. Figure 1 below shows a schematic diagram of a CA 7-segment LED. The letters as shown denote the particular led segment.
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Digital I/O Laboratory DIO-2 © San José State University Dept. of Mechanical and Aerospace Engineering rev. 3.01 25FEB07 Figure 1. 7-segment LED Display (Common Anode (CA) type. Power is applied to both common anode pins (pin 13 and pin 14). A segment is lit when its cathode is then grounded through a current limiting resistor . Pin positions are numbered from 1 to 18. Two of the physical pins on the display are tied together (made ‘common’). For the CA-type of display, the two pins connect to the common anode. For the CC-type of display, the two pins connect to the common cathode.
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This note was uploaded on 09/08/2010 for the course ME 106 at San Jose State University .

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5digital_IO-atmel - Digital I/O Laboratory DIO-1 Digital...

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