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Architecture of a Typical Microcontroller

Microcontrollers are the building blocks of any digital signal processing system. In layman’s terms, they can be described as miniature computers that are present on chips. They consume very little amount of power and are self sufficient. They are similar to microprocessors but contain some additional elements such as read only memory in the form of EEPROM (Electrical Programmable Read Only Memory) and a read write memory that usually utilises flash technology. Another difference between microcontrollers and microprocessors is the clock speed. Microcontrollers usually operate at low clock speeds. Low clock speeds are adopted as they are suitable for the operations that are usually performed using microcontrollers. Also, this ensures that they consume less power.

About Digital Signal Processing

Today, signals, i.e., quantities that fluctuate over time with high frequency, have acquired a great amount of importance and are being used in many fields, especially communication. Digital signal processing involves converting digital data into signals, making its transfer easier and subsequently converting these signals back into the original form. A signal has many characteristics or domains such as time domain, spatial domain, frequency, wavelet domain, etc. Anyone among these can be used to process a respective signal. From among these, the engineer usually selects the one that best represents the characteristics of the signal concerned or, in other words, the one from which data can be obtained easily. To ascertain the required characteristic, the engineer may try out many among these properties. The use of signals has gone up especially with the use of computers. Computers can analyze and process only digital (discrete) data and cannot handle analog (continuous) data. Thus, conversion of the signal from analog to the digital form becomes necessary. The digital signal is exactly similar to the analog signal that it has been obtained from; some mathematical techniques such as the Nyquist-Shannon sampling theorem are used. Usually, after analysis or transformation, the output signal is…

AVR DDS signal generator V2.0

Finally, the second version of the improved AVR DDS signal generator is here. THE first AVR DDS V1.0 generator was only an attempt to run the DDS algorithm without any analog amplitude control. In this DDS generator version, I still wanted to keep things as simple as possible using a minimum count of widely available components in the updated circuit. Also, I kept a single-sided PCB approach. AVR DDS specification AVR DDS signal generator V2.0 is a firmware-based DDS signal generator that uses a slightly modified Jesper’s mini DDS algorithm adapted to AVR-GCC C code as in-line ASM. The AVR DDS signal generator has two outputs – one for DDS signal and another for high speed [1, 8MHz] square signal – which may be used to bring back to life microcontrollers with wrong fuse settings for other purposes where a high-speed square signal may be needed. A high-speed (HS) signal is output directly from the Atmega16 OC1A(PD5) pin. The DDS output is used for all complex signals generated via the R2R resistor network and is adjusted via LM358N offset and amplitude regulating circuits. Two potentiometers can control offset and amplitude. The offset can be controlled in range +5V..-5V while magnitude…

Embedded Systems: microprocessors and microcontrollers

An embedded system is a type of computer that can perform a few specialized tasks. This design is contrary to the normal computer designed to perform many operations that are unrelated to each other in many cases. Embedded systems are present in many of the devices used today and act as their control units. The main issue with embedded systems is their optimality in terms of cost, space and power consumption, etc., as there is no focus on increasing the functionality of the device. The term embedded system can thus, be used to refer to devices that perform certain specific functions and cannot be used to perform others by loading applications on them. Typical features of embedded systems Many of the embedded systems have several hardware restraints as they have to process real-time inputs and be safe to use. Others may not have some of these constraints, and thus, a reduction in the cost of the hardware used is possible. The term embedded system does not refer to isolated devices but rather, they are a part of the device they control or perform some other task in. The software that is used in embedded systems is usually termed firmware. The…

Encoding and modulation of digital signals

We know that digital signals are stored as binary numbers in memory cells. Let’s see how these digital signals can be transferred, in other words – how they can be encoded into electrical signal shape. When the signal has to be sent, it has to be modulated. Pulse Code Modulation (PCM) Probably the simplest and the most common modulation method is pulse code modulation (PCM). In CPM, coding information is modulated as voltage levels. If the supply voltage is 5V, then binary”1″ is represented as +5V while 0 as 0V level. Only two voltage levels are used to modulate the signal. The signal can be sent in parallel (bus mode) or serial mode. In parallel mode whole (let’s say 8 bit) signal can be sent at once via 8 wires, while in serial mode, data has to be sampled in time. This transmission method is most popular in embedded systems. For instance, ADC sends converted data to DSP using CPM. CPM method is OK, but it has several drawbacks like the number of wires required for parallel buses. Still, probably the most dangerous problem is that transmission may experience skew problems when each data wire may have different time delays…

DSP processors and their characteristics

The processing of the various signals is carried out through implements that are together called DSP hardware. This includes the hardware that is used for transmission of signals, multiple devices that are used to enhance or filter the signals, analog to digital and digital to analog converters, and other processing equipment such as computers. Among the hardware mentioned above, digital signal processors are the ones in which the actual processing occurs. Usually, the digital signal processors today have the following characteristics: They are equipped to handle real-time processing, i.e., they can give the optimal performance even when streaming data is being fed into them. The memories that are used to store programs are different from the ones used to store data. They do not provide hardware that supports multitasking. It can be used as a direct memory access device in supporting or host environments. They take analog signals as input, convert them into the digital form, process the signals, and then, Specific them back into the analogous form. They make use of the Direct Memory Access technique. The digital signal processors usually have architecture so as to optimise the following features:

Printed Circuit Board (PCB) Technologies

The term circuit technology usually refers to the various techniques used in the manufacture of electrical circuits. A large number of devices that are used today make use of printed circuit boards (PCBs). These devices provide mechanical support for the various components present within the given device and the components’ electrical connections. The electrical connections present on the PCB are made out of copper sheets laminated on a non-conducting material. Initially, a large copper sheet is laminated on the board, and then the sections that are not required are removed. Various techniques are used for the removal of unwanted copper. Some of them are: Silk Screen Printing: In this technique, an etching-resistant ink is applied to those required areas, and the remaining part is etched off. Photoengraving: Here, a photomask of the circuit required is prepared using the desired software, and then it is applied to the blank PCB. After this, the portions that are not required are etched off. PCB Milling: In this technique, a mechanical milling system that can work on 2 or 3 dimensions is used to remove the copper. The milling system is controlled by software. In some other techniques, only the required copper is added…

Biosignal Properties

The term Biosignal refers to all the signals generated in the human body or any other living organism. More specifically, it represents all those signals from living organisms that are monitored to obtain certain usage information. Primarily, the term refers to electrical signals in nature, but some non-electric signals are monitored. Typically, the changes in potential difference across a certain tissue in the body are measured in the case of bio-electric signals. Let us have a look at a few of the properties of biosignals generated by the human body that are analyzed to obtain information: Electroencephalography In the case of Electroencephalography, the activity of the human brain is monitored. Usually, at a synapse (junctions between the nervous system cells), the flow of ions occurs. This results in the formation of various signals that are used by the body to transfer information. The voltage variations caused by these signals are recorded, and thus, the brain’s activity is measured. Magnetoencephalography In Magnetoencephalography, the magnetic fields produced by the variations of electric currents that form the brain activity are monitored. For this, devices such as SQUID (Superconducting Quantum Interface Devices) are used to have high sensitivity. Many difficulties are faced one tries…

Digital Signal Processing – Applications

Digital signal processing is the technique used to analyze various digital signals and obtain information from the same. It is also used to transfer information from one place to another and involves conversion between analog and digital signals. It finds its application in various areas ranging from broadcasting to medicine. Let us have a look at some of the applications of the same. Biomedical Applications DSP is used extensively in the field of biomedicine. In it, the various signals generated by the different organs in the human body are measured to find information regarding the health of the same. For example, in the case of electrocardiograms, the electric signals generated by the heart are measured. Similarly, the activity of the brain is monitored by electroencephalograms. Automatic Control These days, many gadgets are available that can perform their tasks automatically. These devices contain various components that can take inputs depending on the surrounding conditions. These are conveyed to the device’s control unit, where they are processed, and the necessary action is taken. For example, a device like a thermostat increases its resistance in proportion to temperature. This can be used to stem the current in a machine whenever the temperature rises.

Overview of Programmable Logic Devices

These are devices that are used in electronic circuits to make reconfiguration of the same possible. The logical gates that are normally used perform a fixed function; however, the Programmable Logic Devices (PLD) do not perform any predefined task when manufactured and need to be programmed before they can be used.Before the introduction of PLDs, ROM (Read Only Memories) was used. EPROM could be programmed using any standard hardware for that device and hence, did not require any other peripheral hardware. Another advantage of ROMs is that a particular binary code stored in it could be obtained on any of the n output lines available. Thus, they can be programmed in any way one wishes to. However, ROMs have some disadvantages when they are used as PLDs. They do not produce the outputs as quickly as other devices; they are not very dependable as far as asynchronous inputs are concerned; they require more power, etc. The first PLD was the programmable logic array developed from ROAM (Read-Only Associative Memory) by modification of one of its metal layers and 17 inputs and 18 outputs.