Disadvantages Of Embedded Systems

• Drawbacks Of Embedded Systems
• Disadvantages Of Embedded Systems
• Advantages & Disadvantages Of Embedded Systems
• Advantages & Disadvantages Of Embedded Operating Systems

C++ Tutorial - Embedded Systems Programming - 2020

Advantages And Disadvantages of Embedded Systems - PTInstitute. Why C Is The Preferred Language For Embedded Systems - PTInstitute. Disadvantages of Embedded System. Here, are important cons/ drawbacks of using Embedded system. To develop an embedded system needs high development effort. It needs a long time to market. Embedded systems do a very specific task, so it can't be programmed to do different things. Embedded systems offer very limited resources for memory.

Embedded Systems interview Questions. List few advantages and disadvantages of embedded system? Posted On: Aug 31, 2020. Related Questions. An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electrical system. It is embedded as part of a complete device often including electrical or electronic hardware and mechanical parts. Because an embedded system typically.

When we talk about embedded systems programming, in general, it's about writing programs for gadgets.

Gadget with a brain is the embedded system. Whether the brain is a microcontroller or a digital signal processor (DSP), gadgets have some interactions between hardware and software designed to perform one or a few dedicated functions, often with real-time computing constraints.

Usually, embedded systems are resource constrained compared to the desktop PC. Embedded systems, typically, have limited memory, small or no hard drives, and in some cases with no external network connectivity.

Picture: https://blogs.akamai.com - The Performance Arms Race

Picture: Programming languages for embedded systems

Presentation Materials: Effective C++ in an Embedded Environment (pdf) by Scott Meyers, 2012

Presentation Materials: Embedded Systems Programming (ppt)
by Bjarne Stroustrup
or get it from http://www.stroustrup.com/Programming/.

According to LinuxDevices.com, Linux has emerged as the dominant OS for embedded systems, and it will reach 70% of the market by 2012.

Go to Embedded Linux.

Here are some characteristics of embedded systems, and few systems suffer all of these constrains.

1. Reliability - failure is very expensive.
2. Limited Resources - A resource is something of which a machine has only a limited supply. As an embedded systems programmer, we get it through some explicit action such as 'acquire' or 'allocate' and return it through 'release', 'free', or 'deallocate' to the system. It could be memory, file handles, network connection or communication channels such as sockets, and locks. Or it could be processor cycles, power.
3. Real-time Response.
4. A system may be Running Forever.

The characteristics of embedded systems affect the embedded systems programming:

1. Correctness - producing the results at the right time, in the right order, and using only an acceptable set of resources.
2. Fault tolerance
3. No downtime.
4. Real-time constraints.
   1. hard real time: if a system's response must occur before a deadline
   2. soft real time: same as the hard real time but an occasional miss can be affordable
5. Predictability - In programming embedded systems, predictability usually means the predictability of the time it takes for certain operation. So, operations that are not guarantee a response within a given time, should not be used. For example, a linear search of a list is an unpredictable operation because its number of elements is unknown.
6. Concurrency.

Drawbacks Of Embedded Systems

So, when we do embedded systems programming, we should be aware of the environment and its use. In other words, domain knowledge is essential for designing and implementing a system with a good protection against errors.

1. We're dealing with specialized features of RTOS.
2. We're using a non-hosted environment. In other words, we're using a language right on top of hardware without any protection or help from the traditional OSs.
3. We're dealing with device drivers/hardware device APIs.

Following features of C++ language are not predictable:

1. new and delete
   

   1. Static memory poses no special problem in embedded systems programming since all is taken care of before the program starts to run and long before a system is deployed.

   2. Stack memory can be a problem because it is possible to use too much of it. One way is to avoid recursive functions and stick to iterative implementation.

   3. Dynamic memory allocation is usually banned or restricted. The new and malloc() are either banned or using them is restricted to a startup period, and delete is banned because of the predictability and fragmentation.

      1. predictability - allocation delays
         The time it takes to find a free chunk of memory of a specific size depends on what's been already allocated.
      2. fragmentation
         After several memory allocations, fragments (hole) may take up much of the memory.

   However, there are two data structures that are particularly useful for predictable memory allocations: stacks, pools, and global objects :

   1. Pool is a data structure from which we can allocate object of a given type and later deallocate such object. A pool contains a maximum number of objects; that number is specified when the pool is created. So, it gives us constant time operations without any fragmentation.
   2. Stack is a data structure from which we can allocate chunks of memory and deallocate the last allocated chunk. Stacks grow and shrink only at the top without any fragmentation, and it guarantees constant time operation.
   3. global objects can be allocated at startup time so that set can set aside a fixed amount of memory.
   4. C++ standard library containers such as vector, map, etc. and the standard string are not to be used because they indirectly use new.

2. Exceptions
   How can we catch all exceptions and how long it will take to find a matching catch.
   The throw is typically banned in hard real-time applications. Instead, we may rely on return codes to do error handling.

Disadvantages Of Embedded Systems

Avoid language features and programming techniques that have proved error-prone. Pointers!

1. Explicit conversions which are unchecked and unsafe - avoid them.
1. unchecked conversion
   Embedded systems often require a programmer to access a specific memory location (0xffa2): In this low-level programming, we should be aware that the correspondence between a hardware resource (register's address) and a pointer to the software that manipulates the hardware resource is brittle. Though the reinterpret_cast from an int to a pointer type is crucial link for connections between an application and its hardware resources, we should not expect a code using (unchecked) reinterpret_cast to be portable.
2. Passing pointers to array elements - An array is often passed to a function as a pointer to an element. Therefore, they lose their size, so that the receiving function cannot directly tell how many elements are pointed to. This is a cause of many bugs.

Realtime applications are those that need to respond in a timely fashion to input.Frequently, such input comes from an external sensor or a specialized input device,and output takes the form of controlling some external hardware.

Although many realtime applications require rapid responses to input, thedefining factor is that the response is guaranteed to be delivered within a certaindeadline time after the triggering event.

The provision of realtime responsiveness, especially where short responsetimes are demanded, requires support from the underlying operating system.

However, most OS does not natively provide such support because the requirements ofrealtime responsiveness can conflict with the requirements of multiuser timesharing operating systems.

Realtime variantsof Linux have been created, and recent Linux kernels are moving toward full native support for realtime applications.

Picture source: OS for embedded systems - Embedded Market Study, 2013

An RTOS is an operating system designed to meet strict deadlines which associated with tasks. In RTOS, therefore, missing the deadline can cause undesired or even catastrophic outcome.

I/O Latency

The followings are the characteristics of RTOS:

1. Context switching latency:
   Context switch latency is the time from one context switching to another and it should be short. In other words, the time taken while saving the context of current task and then switching over to another task should be short.In general, switching context involved saving the CPU's registers and loading a new state, flushing the caches, and changing the virtual memory mapping. Context switch latency is highly architecture dependent and different hardware may get different results.
2. Interrupt latency:
   Interrupt latency is the time from interrupt generation until the interrupt service routine starts executing.
   Factors that affect interrupt latency include the processor architecture, the processor clock speed, the particular OS employed, and the type of interrupt controller used.
   Minimum interrupt latency depends mainly on the configuration of the interrupt controller, which combines interrupts onto processor lines, and assigns priority levels (visit Priority Inversion) to the interrupts.
   Maximum interrupt latency depends mainly on the OS.
   For more on Interrupt and Interrupt Latency, please visit my another page Interrupt & Interrupt Latency
3. Dispatch latency:
   The time between when a thread is scheduled and when it begins to execute. Theoretically, in a preemptive OS the dispatch latency for a high-priority thread should be very low. However, in practice preemptive OSs are non-preemptive at times; for example, while running an interrupt handler. The duration of the longest possible non-preemptive interval is said to be the worst-case dispatch latency of an OS.
4. Reliable and time bound inter process mechanisms should be in place for processes to communicate with each other in a timely manner.
5. Multitasking and task preemption:
   An RTOS should have support for multitasking and task preemption. Preemption means to switch from a currently executing task to a high priority task ready and waiting to be executed.
6. Kernel preemption:
   Most modern systems have preemptive kernels, designed to permit tasks to be preempted even when in kernel mode.
   The bright side of the preemptive kernel is that sys-calls do not block the entire system.
   However, it introduces more complexity to the kernel code, having to handle more end-cases, perform more fine grained locking or use lock-less structures and algorithms.
7. Note: Preemptive:
   Preemptive means that the rulesgoverning which processes receive use of the CPU and for how long are determined by the kernel process scheduler.

*Most of the requests are spending time just waiting due to I/Os

In code meant to be portable, use should use to make sure our assumption about sizes is correct.Here is the list of sizes of the primitive types:

1. bool - 1 bit, but takes up a byte
2. char - 8 bits
3. short - 16 bits
4. int - 32 bits, but many embedded systems have 16-bit ints
5. long int - 32 bits or 64 bits

Outoput is:

In the code, to print the individual bits of the integer, we used a standard library bitset:

A bitset is a fixed number of bits. In the above example, we used the number of bits in an int, which is 8*sizeof(int). Then, we initialized that bitset with i.

Another example:

Output is:

Let's look at the following example which looks innocent.

When we compile it, we get a warning something like this:

That's because the index i is signed integer, but v.size() is unsigned integer. Mixing signed and unsigned could lead to disaster. For instance, the loop variable i might overflow. In other words, v.size() might be larger than the largest signed int. Then, i would reach the highest value that could represent a positive integer in a signed int. Then, the next ++ couldn't yield the next-highest integer and would instead result in a negative value. The loop would never terminate!

Here, we have two choices:

1. vector::size_type
2. iterator

The size_type is guaranteed to be unsigned, so the first form has one more bit to play with than the int version. That can be significant, but it is still gives only a single bit of range. The loop using iterators has no such limitation.

Here is an advice on arithmetic operation with unsigned integer by Bjarne Stroustrup

'Avoid that when you can
-Try never to use unsigned just to get another bit of precision
-If you need one extra bit, soon, you'll need another
-Don't mix signed and unsigned in an expression
You can't completely avoid unsigned arithmetic
Indexing into standard library containers uses unsigned000b
(in my opinion, that's a design error)'

For more on the issue of signed integer and unsigned integer in the embedded systems programming, please visit the following pages:

When do we need to manipulate bits?

1. flags as hardware indicators
2. low-level communications - we need to extract from byte streams
3. graphics - we need to compose picture out of several images
4. encryption

Here is an example of extracting information from a short integer.

Output is:

Advantages & Disadvantages Of Embedded Systems

The operations are known as shift and mask. We shift to place the bits we want to consider to the rightmost (least significant) part of the word where they are easy to manipulate. We mask using and (&) together with a bit pattern such as 0xff to eliminate the bits we do not want in the result.

Here is another example clearing 1st and 3rd bits:

Output:

Example: enum, bit set and testing bits:

Bit Field example:

When we use the following structure, we end up using just 4 byte rather than 4+4+4+4=16 bytes:

For more on bit manipulation, please visit
http://www.bogotobogo.com/cplusplus/quiz_bit_manipulation.php where the following issues are discussed:

For keywords such as volatile or const volatile, visit C++ Keywords.

From wiki

Firstly, Embedded processors can be broken into two broad categories: ordinary microprocessors (µP) and microcontrollers ((µC), which have many more peripherals on chip, reducing cost and size. Luger serial number letters. Contrasting to the personal computer and server markets, a fairly large number of basic CPU architectures are used; there are Von Neumann as well as various degrees of Harvard architectures, RISC as well as non-RISC and VLIW; word lengths vary from 4-bit to 64-bits and beyond (mainly in DSP processors) although the most typical remain 8/16-bit. Most architectures come in a large number of different variants and shapes, many of which are also manufactured by several different companies.

A long but still not exhaustive list of common architectures are: 65816, 65C02, 68HC08, 68HC11, 68k, 8051, ARM, AVR, AVR32, Blackfin, C167, Coldfire, COP8, Cortus APS3, eZ8, eZ80, FR-V, H8, HT48, M16C, M32C, MIPS, MSP430, PIC, PowerPC, R8C, SHARC, SPARC, ST6, SuperH, TLCS-47, TLCS-870, TLCS-900, Tricore, V850, x86, XE8000, Z80, AsAP etc.

1. COMs gain traction as time-to-market accelerators for OEMs

   By combining COM express modules with off-the-shelf COMs, suppliers are able to offer several different configurations of CPU boards and leverage COMs' interchangeable characteristics. CPU vendors can thus offer a fairly wide range of boards without incurring high design and inventory carrying costs.

2. PC/104 module family under pressure

   Although VDC data projects the PC/104 family will experience a single-digit rebound from the low points of the recent recession, vendors will have to commit resources to developing newer strategies in order for this technology to remain viable. Otherwise, the recovery of these architectures is likely to stall or decline in 2011.

3. Asia continues to rise in the development of embedded technology

   2011 will see further strengthening of the Asian embedded supplier community as supply chain synergies, R&D; capabilities and fabrication automation increases between upstream and downstream ecosystem partners.

4. China's growth will power MCU market

   Continued economic growth in China will drive the country's automotive market and expand the need for MCU (microcontroller unit) technology. Despite reduction in government subsidies, VDC expects the Chinese automotive market to expand substantially through 2015, driving adoption of MCU solutions.

5. Suppliers will invest in services value chain

   While embedded hardware margins show signs of stability in 2011, it's clear to VDC that leading embedded suppliers also recognize the value their clients place on a range of services capabilities. As a result, many leading suppliers will try to differentiate by investing in critical aspects of the services value chain, from consulting capabilities to enhanced warranty and end-of-life policies.

6. FPGA and GPU will expand into a number of market segments

   The medical, industrial automation and military segments provide an attractive opportunity for FPGA (Field Programmable Gate Array) devices. https://downnup236.weebly.com/win-a-day-casino-bonus.html. From imaging equipment to diagnostic devices, there is a need for adaptable health care, factory control and military C4 solutions. The programmability, flexibility and reduced NRE (non-recurring engineering) costs associated with FPGAs will lend themselves to broader adoption in these markets.

7. Tier 2/Tier 3 OEMs and ISVs will become more important

   Investment in solutions requiring embedded platforms continues to rebound; however, the market will still be driven by small- to mid-sized projects. This is related to the slow return of larger, blanket purchase orders let by Tier 1 accounts and to the user community preferences for projects with smaller footprints that fit within narrower application definitions and require short, sharply defined systems integration support. These projects are tailor-made for local, expert ISVs and ISIs, as well as Tier 2/Tier 3 OEMs.

8. The market explores HaaS (Hardware as a Service) bundles

   Broad market expansion and deep application penetration of remote monitoring and control capabilities will advance across a number of market segments, foretelling a broader migration to managed services solution development and deployment models in supervisory monitoring and control applications. These embedded application clouds will require local points of presence (POPs) or on-site infrastructure and hardware rolled into service level agreements (SLAs) supporting the software and service delivery portions of contracts.

9. Cross-platform processor suppliers learn to play nice

   From broader, bigger, more aggressive, public licensing agreements to M&A;, the market will force suppliers of CPU, FPGA and GPU (graphics processing unit) technologies to collaborate more in 2011. VDC Research's surveys of hundreds of OEMS across a number of embedded markets reveal significant growth in OEM plans to develop solutions on hybrid platforms incorporating two or more of these technologies.

10. Competition will intensify and growth will accelerate

    Even if the market does not return to pre-recession levels, growth will accelerate during 2011. VDC sees virtually every vertical market growing more than five percent, and most technology categories achieving the same five percent CAGR. However, profitability results may not be so positive. Demand for stable technologies, brutal price concessions and expanded services requirements will provide opportunities for differentiation and revenues, but not necessarily margin.

11. Android to catalyze further growth in commercial Linux market

    As device manufacturers take Android into new application classes beyond mobile, the commercial Linux market will experience further growth.

12. Multi-OS systems will grow in designs

    More application classes will have sophisticated UI functionality that is not supported by traditional OSs and end-users will seek out multi-OS systems.

13. Virtualization in embedded and mobile systems will increase

    Driven by hardware bill of materials savings and reduced concerns regarding additional run-time execution latencies and costs, operating system virtualization will provide increased growth opportunities, and therefore will continue to be a significant focus for many suppliers.

14. Symbian's loss to become MeeGo's gain Nacho libre free.

    Intel's increasing focus on embedded combined with Symbian's loss of strategic direction will drive additional gains for MeeGo as Nokia turns their attention toward the Linux-based platform.

15. OEMs to increase focus on the use of web security test tools

    Increased interaction with the cloud and web-based content by more embedded device classes will increase OEM focus on use of web security test tools.

16. Telecom vertical will reaccelerate spend on commercial products

    The increasing burden of mobile device data usage is driving the need for investment in wireless infrastructure and the telecom vertical market will reaccelerate spending on commercial products.

17. Microsoft will regain relevance in the mobile phone sector

    Riding the wave of Windows Phone 7 buzz, Microsoft will re-emerge as a leading player in the mobile phone arena.

18. Another acquisition to come?

    Following a string of high profile acquisitions in 2009/2010, VDC anticipates yet another major embedded real-time operating system supplier will get acquired in 2011.

From wiki

Embedded Linux is the use of Linux in embedded computer systems such as mobile phones, personal digital assistants, media players, set-top boxes, and other consumer electronics devices, networking equipment, machine control, industrial automation, navigation equipment and medical instruments. According to survey conducted by Venture Development Corporation, Linux was used by 18% of embedded engineers.

Linux has been ported to a variety of processors not always suited for use as the processor of desktop or server computers, such as various CPUs including ARM, AVR32, Blackfin, ETRAX CRIS, FR-V, H8300, IP7000 M32R, m68k, MIPS, mn10300, PowerPC, SuperH, or Xtensa processors, as an alternative to using a proprietary operating system and toolchain.

The advantages of embedded Linux over proprietary embedded operating systems include no royalties or licensing fees, a stable kernel, a support base that is not restricted to the employees of a single software company, and the ability to modify and redistribute the source code. The disadvantages include a comparatively larger memory footprint (kernel and root file system), complexities of user mode and kernel mode memory access and complex device drivers framework.

There are non-proprietary embedded operating systems that share the open-source advantages of Linux, without the memory requirements that make Linux unsuitable for many embedded applications.

In our day-to-day life we frequently use many electrical and electronic circuits and kits which are designed using embedded systems technology. The electrical and electronics engineering students and electronics and communications engineering students are required to design final year electronics projects to gain hands on experience with the real time embedded systems and also to fulfill the engineering graduation criteria. The engineering final year electronics projects are designed using embedded systems and applications. The computers, mobile phones, tablets, laptops, digital electronic systems, and other electrical and electronic gadgets are designed using embedded systems. So, let us know what is embedded system and applications of embedded systems.

What is Embedded System?

The electronic system which integrates the hardware circuitry with the software programming techniques for providing project solutions is called as embedded systems. By using this embedded system technology the complexity of the circuits can be reduced to a great extent which further reduces the cost and size. Embedded system was primarily developed by Charles Stark for reducing the size and weight of the project circuitry.

An embedded system is basically an electronic system that can be programmed or non-programmed to operate, organize, and perform single or multiple tasks based on the application. In the real time embedded systems, all the assembled units work together based on the program or set of rules or code embedded into the microcontroller. But, by using this microcontroller programming techniques only a limited range of problems can be solved.

Embedded Systems Hardware

Every electronic system consists of hardware circuitry, similarly, embedded system consists of hardware such as power supply kit, central processing unit, memory devices, timers, output circuits, serial communication ports, and system application specific circuit components & circuits.

Advantages & Disadvantages Of Embedded Operating Systems

Embedded Systems Software

An embedded system is integration of hardware and software, the software used in the embedded system is set of instructions which is termed as a program. The microprocessors or microcontrollers used in the hardware circuits of embedded systems are programmed to perform specific tasks by following the set of instructions. These programs are primarily written using any programming software like Proteus or Lab-view using any programming languages such as C or C++ or embedded C. Then, the program is dumped into the microprocessors or microcontrollers that are used in the embedded system circuits.

Embedded System Classification

Embedded systems are primarily classified into different types based on complexity of hardware & software and microcontroller (8 or 16 or 32-bit). Thus, based on the performance of the microcontroller, embedded systems are classified into three types such as:

• Small scale embedded systems
• Medium scale embedded systems
• Sophisticated embedded systems

Further, based on performance and functional requirements of the system embedded system classified into four types such as:

• Real time embedded systems
• Stand alone embedded systems
• Networked embedded systems
• Mobile embedded systems

Applications of Embedded Systems

Embedded systems find numerous applications in various fields such as digital electronics, telecommunications, computing network, smart cards, satellite systems, military defense system equipment, research system equipment, and so on. Let us discuss a few practical applications of embedded systems that are used in designing embedded projects as a part of engineering final year electronics projects.

IOT Based Energy Meter Reading Through Internet

Internet of Things-IOT based energy meter reading through the internet is an innovative application of real time embedded systems. Using this project you can avail the facility of displaying (in the format of chart and gauge) units of power consumed and the cost of consumption over the internet.

Digital energy meter is used for designing innovative embedded projects, this digital energy meter blinking LED will flash around 3200 times for one unit, this LED signal and microcontroller are interfaced using a light dependent resistor (LDR). Thus, whenever LED flashes, this blinking will activate the LDR sensor, that sends an interrupt signal to the microcontroller for each flash of LED. Based on the interrupts received by the microcontroller, it will display the reading of energy meter on an LCD display which is interfaced it.

This project consists of a GSM modem which is interfaced to the microcontroller using RS232 link and level shifter IC. The reading of energy meter can be sent to the GSM modem, SIM used in this GSM modem is enabled with internet facility. Thus, the energy meter can be directly transmitted to a specific web page to display it over the internet and view in the format of graphical representation from anywhere in the world.

Engineering students are fascinated to design more innovative embedded projects as their final year electronics projects. Thus, here we are providing a list of real time electronics projects on embedded systems.

• Internet (IOT) of Things based underground cable fault distance display using GSM
• Electronic passport system using smart card
• Patient body temperature monitoring remotely using Internet of Things (IOT)
• Power saver for street light using high sensitive LDR managed by Arduino
• GSM based prepaid energy meter
• Automatic meter reading system using Zigbee
• A notice board display system using voice commands using an Android phone
• Home automation using voice commands
• Solar based electric fencing system to deter cattle

Are you an engineering student or electronics hobbyist, do you have any innovative ideas to implement embedded projects practically? Then, you are appreciated to post your ideas in the comments section below. So, that let us and other readers also try to provide project solutions for your ideas.