L3 - Embedded Hardware

Question 1

What do we understand under a synchronous interrupt? Name an example.

Answer 1

Occur at the same time. E.g.: Exception, Segmentation Fault or Division by zero.

Question 2

Name five characteristics of a microcontroller.

Answer 2

1. many interrupts
2. high I/O functionality
3. low level processing
4. interfacing with sensor/actuators
5. low cost

Question 3

What are characteristics of FPGA?

Answer 3

FPGA have reprogrammable hardware (VHDL, Verilog) and are very fast in execution of logic operations.

Question 4

What are FPGA?

Answer 4

FPGA (Field Programmable Arrays) are a combination of standard hardware (e.g. DSP) and fully application specific hardware (e.g. ASIC).

Question 5

What are characteristics of a Heap?

Answer 5

• Memory allocation dynamically (memory size does not have to be known @compile time)
• must be managed (allocation & deallocation)

Question 6

Which companies do produce microprocessors?

Answer 6

Intel, AMD and ARM.

Question 7

Name on advantage and disadvantage of interrupts.

Answer 7

• PRO: resources only used when needed
• CON: execution is interrupted in non-deterministic manner

Question 8

A Gyroscope…

Answer 8

A Gyroscope measures angular velocity around an axis and is often combined with an accelerometer for an inertial measurement unit (IMU)

Question 9

Is a microcontroller faster than a microprocessor?

Answer 9

Compared to a microprocessor, a microcontroler is relatively slow but does not need many external parts, has a low energy consumption and a low cost.

Question 10

What is an ADC and what is its task?

Answer 10

An ADC (Analog Digital Converter) circuit maintains input during conversion time. To cut off the higher frequencies before sampling, an antialiasing filter is necessary and prevents higher frequency noise from disturbing low frequency signals.

Question 11

An embedded system should be ______________.

Answer 11

reliable

Question 12

What are the tasks of a DSP?

Answer 12

A DSP is optimized for signal processing such as:

• filtering
• system identification
• frequency analysis
• machine learning
• feature extraction

Question 13

H-Bridges are used …

Answer 13

H-Bridges are used to drive large loads and switches driven by PWM (magn. coils, motors)

Question 14

In which kind of applications are Embedded Systems used? Name two.

Answer 14

• simple control tasks in household appliances
• entertainment electronics
• communication systems
• automotive applications
• control of complex automation systems in industrial environments

Question 15

What are interrupts?

Answer 15

normal execution is automatically interrupted when environment changes

Question 16

Name on advantage and disadvantage of polling.

Answer 16

• PRO: short latencies (low number of IOs), events do not block execution of the program
• CON: unnecessary polls, high CPU usage, reaction dime depends on number of IOs

Question 17

What is polling?

Answer 17

continuously poll I/Os for a change

Question 18

Reduced instruction set RISC (ARM)

Answer 18

• simple machine instructions
• used in embedded systems (real-time hardware)

Question 19

What is a Cache?

Answer 19

A cache is a very fast memory that stores data which is often accessed. While making timing issues difficult to analyse, it improves drastically execution and access times.

Question 20

What is the name of a memory segment in RAM that is organised as LIFO?

Answer 20

Stack.

Question 21

What is a key requirement for embedded processors? What mechanisms are not acceptable?

Answer 21

In RTS deterministic behaviour is essential to guarantee high accuracy. Non-deterministic mechanisms (e.g. Virtual Memory, Garbage Collection, Asynchronous IO requests, Recursive function calls) are unwanted.

Question 22

What is an ASIC?

Answer 22

An ASIC (Application Specific Integrated Circuit) are tasks that are implemented in hardware design and therefore feasible for large quantities. Their functionality cannot be changed.

Question 23

If an interrupt is caused by an external event, it is called _______________ interrupt. Name an example.

Answer 23

asynchronous. E.g.: timer overrun, end of I/O operation or external pin voltage.

Question 24

Which sensor does measure the acceleration, sense vibrations and is used for navigation?

Answer 24

Accelerometer.

Question 25

A Digital Analog Converter (DAC) …

Answer 25

A DAC converts digital input code (binary) to an analog output voltage.

Question 26

How can a system react to environmental changes?

Answer 26

Polling & Interrupting

Question 27

What are the main steps when executing a task?

Answer 27

1. Fetch instruction
2. Decode
3. Execute on the ALU
4. Memory Access (L/S)
5. Write back into register

Question 28

Complex instruction set CISC (x86)

Answer 28

• maps complexity of common instructions directly in machine code
• timing issues used in general purpose computing

Question 29

Pulse Width Modulation (PWM) delivers …

Answer 29

PWM delivers variable amounts of power to external hardware and is programmable through PWM interface of timer Pulse.

Question 30

What does ALU stand for?

Answer 30

Arithmetic Logic Unit.

Question 31

What is a DSP?

Answer 31

A DSP (Digital Signal Processor) is a high performance ALU (parallelization) and control unit.

Question 32

Encoder

Answer 32

relative position obtained by counting ticks via digital magneto or optical resistant (used in robotics and motor control)

Question 33

Overlapping execution of different tasks can lead to conflicts. Name three different conflicts that can occur.

Answer 33

1. resource hazard
2. data hazard
3. control hazard

Question 34

Name the actuator that reads a bit in a register and sets a voltage of a pin to high or low.

Answer 34

General Purpose IO (GPIO)