Hardware for Embedded System

1. Hardware

This circuit is the circuit that drives usb_comn/ when the control signal is inserted into CHIP1.

If you draw a logic circuit with two bit adders as transistors, you can draw it as follows.

2-bit adder with transistors

2. Signal & Frequency

A signal refers to a physical quantity that varies with time or space, carrying information that can be interpreted by an observer. Signals can be represented as a combination of sine and cosine functions of different frequencies, which are called frequency components. The frequency of a signal refers to the number of cycles or oscillations per unit time of a wave. In the frequency domain, a signal can be decomposed into its frequency components using techniques such as the Fourier Transform, which converts a signal from the time domain to the frequency domain. The frequency domain representation of a signal shows the amplitudes of its frequency components. The DC component of a signal is the portion that has zero frequency and represents the average or offset value of the signal.

In embedded systems, a signal is a physical or electrical quantity that varies over time and can be measured or detected by a sensor or instrument. For example, in a temperature control system, the temperature is a signal that needs to be measured and controlled.

Frequency refers to the rate at which a signal oscillates or repeats over time. It is usually measured in Hertz (Hz) and represents the number of cycles of a waveform that occur in one second. In embedded systems, frequency is often associated with clock signals, which are used to synchronize the operation of various components in a system.

Signal and frequency analysis is an important aspect of embedded systems design and testing. In order to properly design and test a system, engineers need to understand the characteristics of the signals involved, such as their frequency, amplitude, and waveform shape. This can be done through a process called signal analysis, which involves measuring and analyzing the signal using various instruments and techniques.

 

3. Analog, digital signals, and ground.

In electronics and telecommunications, a signal is a physical quantity that carries information. Signals can be broadly classified into two types: analog signals and digital signals.

An analog signal is a continuous signal that varies in time and amplitude, meaning that it takes on a continuous range of values. Examples of analog signals include sound waves, voltage signals, and radio waves. Analog signals are characterized by their waveform, frequency, amplitude, and phase.

A digital signal, on the other hand, is a discrete signal that takes on a limited number of values. It is represented using a series of discrete values, typically binary (0 and 1), which correspond to the presence or absence of an electrical voltage or current. Digital signals are characterized by their bit rate (the number of bits per second), the number of bits used to represent each sample, and the sampling rate (how frequently the signal is measured).

 

 

One of the key advantages of digital signals over analog signals is their ability to transmit information with high accuracy and reliability, even in the presence of noise and interference. However, analog signals can still be advantageous in certain situations, such as in audio and video applications where continuous variations in signal are important for natural and accurate reproduction of the original source.

4. Circuit Theory R (Resistance) L (Inductor) C (Capacitor)

Resistance, inductance, and capacitance are three fundamental components of electrical circuits.

Resistance:
Resistance (symbol R) is a property of a material or component that opposes the flow of electrical current. It is measured in ohms (Ω) and is represented by a resistor in a circuit diagram. Resistors are often used to control the flow of current and to reduce the voltage in a circuit. The higher the resistance, the more it will resist the flow of current through the circuit.

Inductor:
An inductor (symbol L) is a component that stores energy in a magnetic field when current flows through it. It is measured in henries (H) and is represented by a coil of wire in a circuit diagram. Inductors are often used in circuits to block high-frequency signals or to smooth out voltage fluctuations. When the current through an inductor changes, the magnetic field around it also changes, and this induces an opposing voltage in the circuit.

Capacitor:
A capacitor (symbol C) is a component that stores energy in an electric field between two conductive plates. It is measured in farads (F) and is represented by two parallel lines in a circuit diagram. Capacitors are often used to filter out low-frequency signals or to store charge in a circuit. When a capacitor is charged, one plate becomes positively charged while the other becomes negatively charged, and this creates an electric field between them that stores the energy.

Resistance, inductance, and capacitance are three fundamental properties of electrical circuits that play important roles in controlling and manipulating the flow of electrical energy. By combining these components in different ways, engineers can design and build complex electronic devices and systems for a wide range of applications.

Now, in summary, for any given voltage you want, you can set the amount of current.
In the case of R, the larger R, the smaller the current can flow.
In the case of C, the smaller C, the smaller the current can flow.
For L, the larger L, the smaller the current flows.

In terms of frequency, at a given RLC value,
R doesn't take the frequency.
C has less resistance at higher frequencies, (more current flows)
The higher the frequency, the greater the resistance of L. (It's hard for the current to flow)

5. Filter

A filter in an embedded system is an electronic component or circuit that is designed to selectively pass or block specific frequencies of a signal. Filters are often used in embedded systems to remove unwanted noise or to extract specific signals from complex signals.

There are several types of filters that are commonly used in embedded systems, including:

Low-pass filter: This filter allows low-frequency signals to pass through while blocking high-frequency signals.

High-pass filter: This filter allows high-frequency signals to pass through while blocking low-frequency signals.

Band-pass filter: This filter allows signals within a specific frequency range to pass through while blocking signals outside that range.

Band-stop filter (also known as notch filter): This filter blocks signals within a specific frequency range while allowing signals outside that range to pass through.

Filters can be implemented in various ways, including using analog circuits, digital signal processing (DSP), or a combination of both. In analog circuits, filters are often implemented using passive components such as resistors, capacitors, and inductors. In digital signal processing, filters are implemented using algorithms that manipulate the digital signal.

Filters are important in embedded systems because they can improve the accuracy and reliability of the system by reducing noise and interference, and by isolating specific signals that are needed for proper operation. Filters can be found in a wide range of embedded systems applications, including audio processing, communication systems, sensor networks, and more.

6. Transistor

Transistors are widely used in embedded systems as fundamental components to control the flow of electrical signals within the system. They are often used to switch or amplify signals, and to interface between different parts of the system.

In embedded systems, transistors are typically used in two different modes of operation: as switches or as amplifiers.

As switches, transistors are used to turn electrical signals on or off. This can be used to control the flow of current through different parts of the system, to switch on or off specific functions, or to interface with external devices. For example, a transistor might be used to turn on an LED when a specific sensor is triggered, or to switch a motor on or off in response to a particular input.

As amplifiers, transistors are used to increase the amplitude of an electrical signal. This can be used to boost a weak signal, to amplify an audio signal before it is sent to a speaker, or to amplify a sensor signal before it is processed by a microcontroller. Amplifiers are particularly important in embedded systems that rely on sensors to gather data, as they can help to ensure that the signal is strong enough to be accurately measured and analyzed.

There are many different types of transistors that can be used in embedded systems, including bipolar junction transistors (BJTs), field-effect transistors (FETs), and metal-oxide-semiconductor field-effect transistors (MOSFETs). Each type of transistor has its own advantages and disadvantages, and the choice of transistor will depend on the specific requirements of the application.

7. Pull up, Pull down and Open collector

Pull-up and pull-down resistors are commonly used in embedded systems to ensure that digital signals are in a known state when they are not actively driven by an output device.

In digital systems, a signal is typically considered "high" when it is at or above a certain voltage threshold, and "low" when it is below that threshold. However, when a digital input is not connected to anything, it can "float" between these two states, and it may not be in a well-defined state. This can lead to unpredictable behavior and can make it difficult to accurately measure or control the input signal.

To prevent this, pull-up and pull-down resistors are used to ensure that the signal is held in a known state when it is not being actively driven. A pull-up resistor connects the input to a voltage source (usually Vcc), while a pull-down resistor connects the input to ground (GND).

When a pull-up resistor is used, the input is typically pulled to Vcc when it is not actively driven, which ensures that the signal is in a "high" state. Conversely, when a pull-down resistor is used, the input is typically pulled to ground when it is not actively driven, which ensures that the signal is in a "low" state.

Pull-up and pull-down resistors are particularly useful in applications where a digital input is connected to a switch or other input device that may not always be in a well-defined state. By using a pull-up or pull-down resistor, the input can be kept in a known state, which can help to prevent errors and ensure reliable operation of the system.

8. RLC & Transistor

An RLC circuit is a circuit that contains a resistor (R), an inductor (L), and a capacitor (C) connected in series or parallel. The behavior of an RLC circuit depends on the values of these components and the frequency of the input signal.

A transistor can be used in an RLC circuit as a switch or as an amplifier. As a switch, the transistor can be used to turn the circuit on or off, while as an amplifier, it can be used to amplify the input signal.

One example of an RLC circuit with a transistor is a Colpitts oscillator. This circuit uses an inductor, two capacitors, and a transistor to generate a sinusoidal signal at a specific frequency. The inductor and capacitors form a resonant circuit that determines the frequency of the oscillator, while the transistor acts as an amplifier to boost the signal.

In a Colpitts oscillator, the inductor and capacitors are connected in a specific configuration to form a feedback loop. The base of the transistor is connected to the midpoint of the capacitors, while the collector is connected to a power supply and the emitter is connected to ground. When the transistor is turned on, current flows through the inductor and charges the capacitors, which then discharge through the transistor. This cycle repeats, creating a sinusoidal output signal at the resonant frequency of the circuit.

The values of the components in an RLC circuit with a transistor can be adjusted to control the behavior of the circuit. For example, changing the value of the inductor or capacitors can change the resonant frequency of the circuit, while changing the value of the resistor can affect the damping of the circuit. By carefully selecting the values of the components and tuning the circuit, it is possible to create a wide range of different RLC circuits with transistors, each with its own unique behavior and applications.

 

9. Logical circuit

A logic circuit is an electronic circuit that performs a logical operation on one or more inputs to produce an output. Logic circuits are used in a wide range of electronic devices, from simple calculators to complex computer systems.

There are two main types of logic circuits: combinational and sequential. Combinational logic circuits perform logical operations on their inputs using a set of logic gates, which are basic building blocks that can perform logical operations such as AND, OR, and NOT. The output of a combinational logic circuit depends only on the current values of its inputs, and not on any previous values or the state of the circuit.

Sequential logic circuits, on the other hand, have an internal state that can change over time in response to their inputs. This allows them to perform more complex operations, such as storing and processing data. Sequential logic circuits typically use flip-flops or other types of memory elements to store their internal state, and a clock signal to control when the state is updated.

Some common types of logic gates used in combinational logic circuits include:

• AND gate: The output of an AND gate is high (1) only when both of its inputs are high.
• OR gate: The output of an OR gate is high when one or both of its inputs are high.
• NOT gate: The output of a NOT gate is the opposite of its input (i.e., it is high when the input is low, and vice versa).
• NAND gate: The output of a NAND gate is low (0) only when both of its inputs are high.
• NOR gate: The output of a NOR gate is low when one or both of its inputs are high.
• XOR gate: The output of an XOR gate is high when one and only one of its inputs is high.

Logic circuits can be designed and analyzed using boolean algebra and truth tables, which provide a systematic way to represent and manipulate logical expressions. The design and optimization of logic circuits is an important part of digital electronics and computer engineering, and is used in a wide range of applications from consumer electronics to industrial control systems.

 

 1) AND GATE

Connect the two transistors in series as shown. The voltages applied to the base are input A and B, respectively. Both A and B must have a voltage (input must be 1). Electricity flows through the Output.

2) OR GATE

If you connect the two transistors in parallel as shown in the figure, even if a voltage is applied to only one of A and B, the current flows through the corresponding circuit to the output.

3) NOT GATE

If you construct the circuit as shown and A (input) is not applied to voltage, the current is diverted toward the Output. When a voltage is applied to A, the current is dropped in the direction of the grounded ground.