E8.1 and E8.2

Summary A user employs I/O devices to interact with embedded systems. LEDs are often used t indicate whether the product is functioning properly and whether the power is on. LEDS also used to display certain patterns. Matrix displays are based on LEDs and display messages in public buildings. Today, LEDs are even used to provide lighting because of their low power consumption. are often used to A set of DIP switches is used as a simple input device. The software needs to output a sage to remind the user to set up a value in the DIP switches and assert an interrupt to infor the MCU to read the value. mes The AVR Mega and XMega devices have many signal pins. These signal pins into I/O PORTS. An I/O PORT consists of a set of signal pins and registers required for the I/O operation. Because an I/O pin can be used for input and output, the user must co direction of the I/O pin before using it in data transfer. This is achieved by writing an appropri- ate value into a data direction register. For AVR Mega and XMega devices, a pin is configured for output if a l is written to its associated bit position of the PORT data direction register. In addi- tion, the AVR allows the user to configure the input pin sensing edge and pull-up or pull-down. To output data, the MCU writes data to the PORT data register. To input data, the MCU reads from the PORT input register. When interfacing peripheral chips with the microcontroller, the user must make sure that these peripheral chips are electrically compatible with the microcontroller. to convert digital values into voltages. Square, saw-tooth, triangular, staircase, and sinusoidal waveforms can be generated from a D/A converter easily The digital value to be converted can be represented in 8 bits, 10 bits, or many more bits. The more bits are used, the better the resolution gets. A high-fidelity digital audio system uses 24 bits to encode a value to be converted back to audio sound. Exercises E8.1 Write an instruction sequence to output the value 0x53 to PORTA. E8.2 Write an instruction sequence to read the voltage levels on value in register r20 PORTB pins and place the