AVR is a family of microcontrollers, which have the modified Harvard architecture 8-bit RISC single-chip microcontrollers. AVR uses on-chip flash memory for program storage, as opposed to one-time programmable ROM, EPROM, or EEPROM used by other microcontrollers. AVR microcontrollers applications are embedded systems. They are particularly common embedded applications, popularized by their inclusion of open hardware development boards.
An embedded system is a computer system that is part of a larger system or machine. It is a system with a dedicated function within a larger electrical or mechanical system.
The I/O devices of embedded system are classified into two categories
Serial | Input | Output |
• Synchronous : | Audio/Video signal | Audio/Video signal |
• Asynchronous : | Keypad, Mouse, Modem | Printer, Modem |
Parallel | Input | Output |
• Single bit : | Rotation, Threshold sensors | Pulses to external circuit |
• Multi bit : | Vp from ADC, sensors | LCD, Printer |
With embedded system, it is possible to replace dozens or even more of hardware logic gates, input buffers, timing circuits, output drivers, etc. with a relatively cheap microprocessor.
Real-time embedded systems are computer systems that monitor, respond or control an external environment. This environment is connected to the computer system through actuators, sensors, and other input-output interfaces.
The microcontroller is a self-contained system with peripherals, memory and a processor that can be used as embedded system.
Microprocessor is managers of the resources (I/O, memory) which lie outside of its architecture
Microcontroller have I/O, memory, etc. built into it and specifically designed for control
DMA address deals with physical addresses. It is a device which directly drives the data and address bus during data transfer. So, it is purely physical address.
Interrupt latency is a time taken to return from the interrupt service routine post handling a specific interrupt. By writing minor ISR routines, interrupt latency can be reduced.
For embedded system, the buses used for communication includes
While ISA, EISA, PCI are standard buses for parallel communication used in PCs, computer network devices, etc.
Timers in embedded system are used in multiple ways
A watchdog timer is an electronic device or electronic card that execute specific operation after certain time period if something goes wrong with an electronic system.
Embedded systems require infinite loops for repeatedly processing or monitoring the state of the program. For instance, the case of a program state continuously being verified for any exceptional errors that might just happen during run-time such as memory outage or divide by zero, etc.
Some of the commonly found errors in embedded systems are
A semaphore is an abstract datatype or variable that is used for controlling access, by multiple processes to a common resource in a concurrent system such as multiprogramming operating system. Semaphores are commonly used for two purposes
Mutexes | Semaphores | ||||
• A mutex object enables one thread into a controlled section, forcing other threads which tries to gain access to that section to wait until the first thread has moved out from that section | • Semaphore allows multiple access to shared resources | ||||
• Mutex can only be released by thread which had acquired it | • A semaphore can be signaled from any other thread or process. | ||||
• Mutex will always have a known owner | • While for semaphore you won’t know which thread we are blocking on | ||||
• Mutex is also a tool that is used to provide deadlock-free mutual exclusion (either consumer or producer can have the key and proceed with their work) | • Semaphore is a synchronization tool to overcome the critical section problem | ||||
• Mutexes by definition are binary semaphores, so there are two states locked or unlocked | • Semaphores are usually referred to counted locks |
Recursion function can be used when you are aware of the number of recursive calls is not excessive. Inline functions property says whenever it will called, it will copy the complete definition of that function. Recursive function declared as inline creates the burden on the compilers execution.
Semaphore or Mutex cannot be used for interrupt context in Linux Kernel. While spinlocks can be used for locking in interrupt context.
Job markets are shrinking. However, when it AVR microcontroller field, it is expanding rapidly. There are immense career scopes and opportunities available for the candidates skilled in AVR microcontroller. Candidates with in-depth acquaintance and skill-based experience in AVR Microcontroller technology can expect a long survival in the field. Thus, when it is about interview, employers choose to select the skilled candidates, as the projects are very demanding and need quality ideas.
The expected salary of professionals is 42, 000 dollars per annum, which can be increased to double with gaining experience. However, the salary of an experienced AVR Microcontroller depends upon the location, business, and the company’s requirements.
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