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The beaglebone Black processor includes two independent Programmable Real Time Units (PRUs). Hobbyists and professionals are excited about possible use of these units for real-time applications, which is understood. However, if you can have a RTOS (whether for the beaglebone or the raspberry pi), why would you need the PRUs?
EDIT-
For information, the BBB has an ARM Cortex A8 running at 1 GHz, with 1.9 DMIPS / MHz. The PRUs are simple RISCs running at 200 MHz.
Linux, even with the real-time scheduler is unsuited to many critical hard real-time tasks with response requirements at the microsecond level, on the other hand it provides or enables a great deal of functionality in terms of UI, connectivity and filesystem support. These things are either not available in an RTOS or are provided at significant cost in high end RTOS, and with much more limited hardware support.
So if you have a system that has hard-real time constraints, but needs more general purpose computing features such a networking, filesystem connection to commercial-off-the-shelf (COTS) peripherals etc., then the PRU provides a solution to that.
On the other hand I can't help but think that this is a marketing exercise on the part of TI to sell more chips. A similar solution has always been possible (and indeed common) using one or more processors to perform time critical tasks, possibly running an RTOS, while UI and connectivity are handled by a single processor with the necessary hardware and memory resources but without the real-time constraints. The PRU device does have two 32 bit cores, but XMOS xCORE devices have as many as 16 cores - with 16 communicating cores, you may not even need an RTOS.
To answer the question...
[...] if you can have a RTOS [...], why would you need the PRUs?
... directly; you probably wouldn't need them in that case, but you would loose Linux - and your application may need that. It is just one of many solutions to real-time applications using Linux. You pays your money, and takes your choice.
Most likely the processor in BeagleBone or RaspberryPI is too "heavy" for real time - after all, you could run RTOS on your PC, but it will not be very responsive entirely deterministic, even when it's faster than your typical microcontroller (I guess that these PRUs are some sort of microcontrollers with a new fancy name). In such high-level application processor as found on these boards you rarely have direct access to hardware or interrupts, which are essential for real time applications that actually do something time-critical.
my question is : how can build single board computer like Raspberry Pi for run OS ?
user ARM micro processor and debian arm os , can use USB and etc.
like raspberry pi and other single board computer
i search but find nothing for help me !!! :(
The reason you can find nothing is probably because it is a specialist task undertaken by companies with appropriate resources in terms of expertise, equipment, tools and money.
High-end microprocessors capable of running an OS such as Linux use high-pin-density surface mount packages such as BGA or TQFP, these (especially BGA) require specialist equipment to manufacture and cannot reliably or realistically be assembled by hand. The pin count and density necessitates the use of multi-layer boards, these again require specialist manufacture.
What you would have to do if you wanted your own board, is to design your board, source the components, and then have it manufactured by a contract electronics assembly house. Short runs and one-off's will cost you may times that of just buying a COTS development or application board. It is only cost-effective if you are ultimately manufacturing a product that will sell in high volumes. It is only these volumes that make the RPi so inexpensive (and until recently Chinese manufacture).
Even if you designed and had your own board built, that in itself requires specialist knowledge and skill. The bus speeds on such processors require very specific layout to maintain signal integrity and timing and to avoid EMC problems. The cost of suitable schematic capture and board layout software might also be prohibitive, no doubt there are some reasonably capable open source tools - but you will have to find one that generates output your manufacturer can use to set-up their machinery.
Some lower-end 8 bit microcontrollers with low pin count are suitable for hand soldering or even DIP socketing, using a bread-board or prototyping board, but that is not what you are after.
[Further thoughts added 14 Sep 2012]
This is probably only worth doing if one or more of the following are true:
Your aim is to gain experience in board design, manufacture and bring-up as an academic or career development exercise and you have the necessary financial resources.
You envisage high production volumes where the economies of scale make it less expensive than a COTS board.
You have product requirements for specific features or form-factor not supported by COTS boards.
You have restricted product requirements where a custom board tailored to those and having no redundant features might, in sufficient volumes be cost-effective.
Note that COTS boards come in two types: Application modules intended for integration in a larger system or product, and development boards that tend to have a wide range of peripherals, switches, indicators and connectivity options and often a prototyping area for your own use.
I know this is an old question, but I've been looking into the same thing, possibly for different reasons, and it now comes up at the top of a google search providing more reasons not to ask or even look into it than it provides answers.
For an overview of what it takes to build a linux running board from scratch this link is incredibly useful:
http://hforsten.com/making-embedded-linux-computer.html
It details:
The bare minimum you need in terms of hardware ( ARM processor, NAND flash etc )
The complexities of getting a board designed
The process of programming the new chip on the board to include bootloaders and then pointing them to a linux kernel for the chip to boot.
Whether the OP wishes to pursue every or just some of these challenges, it is useful to know what the challenges are.
And these won't be all of them, adding displays, graphics and other hardware and interfaces is not covered, but this is a start.
Single board computers(SBC) are expected to take more load than normal hobby board and so it has slightly complicated structure in terms of PCB and components. You should be ready to work with BGA packages. Almost all of processors in SBCs are BGA (no DIP/QAFP). Here is the best blogpost that I recently came across. Its very nicely designed and fabricated board running Linux on ARM processor. Author has really done a great job at designing as well as documenting the process. I hope it helps you to understand both hardware and software side of SBCs.
A lot of answers are discouraging. But, I would say you can do it, as I have done it already with imx233. Its not easy, its not a weekend project. My project link is MyIMX233.
It took me about 4-5months
It didn't cost me much, a small fine tip soldering iron is what I used.
The hard part is learning to design PCB.
Next task would be to find a PCB manufacturer with good enough precision, and prototyping price.
Next task would be to source components.
You may not get it right, I got the PCB right by my 3rd iteration. After that I was able to repeatedly produce 3 more boards all of which worked fine.
PCB Design - I used opensource KiCAD. You need to take care in doing impedance matching between RAM and processor buses, and some other high speed buses. I managed to do it in 2 layer board with 5mil/5mil trace space.
Component Sourcing - I got imx233 LQFP once via mouser, and once via element14.
RAM - 64MB tssop.
Soldering - I can say its easy to mess up here, but key is patience. And one caution don't use frying pan and solder past to do reflow soldering. I literally fried my first 2 processors like this. Even hot air soldering by a mobile repair shop was also not good enough.
Boot loading image - I didn't take much chance here, just went with Archlinux image by olimex.
If you want to skip the trouble of circuit designing between RAM & processor, skip imx233 and go for Allwinner V3S. In 2017/2018 this would be easiest approach.
Bottom line is I am a software engineer by profession, and if I can do it, then you can do it.
Why not using an FPGA board?
Something with Zynq like the Zybo board or from Altera like the DE0-Nano SoCKit.
There you already have the ARM core, memory, etc... plus the possibility to add the logic you miss.
I am new to the locating hardware side of embedded programming and so after being completely overwhelmed with all the choices out there (pc104, custom boards, a zillion option for each board, volume discounts, devel kits, ahhh!!) I am asking here for some direction.
Basically, I must find a new motherboard and (most likely) re-implement the program logic. Rewriting this in C/C++/Java/C#/Pascal/BASIC is not a problem for me. so my real problem is finding the hardware. This motherboard will have several other devices attached to it. Here is a summary of what I need to do:
Required:
2 RS232 serial ports (one used all the time for primary UI, the second one not continuous)
1 modem (9600+ baud ok) [Modem will be in simultaneous use with only one of the serial port devices, so interrupt sharing with one serial port is OK, but not both]
Minimum permanent/long term storage: Whatever O/S requires + 1 MB (executable) + 512 KB (Data files)
RAM: Minimal, whatever the O/S requires plus maybe 1MB for executable.
Nice to have:
USB port(s)
Ethernet network port
Wireless network
Implementation languages (any O/S I will adapt to):
First choice Java/C# (Mono ok)
Second choice is C/Pascal
Third is BASIC
Ok, given all this, I am having a lot of trouble finding hardware that will support this that is low in cost. Every manufacturer site I visit has a lot of options, and it's difficult to see if their offering will even satisfy my must-have requirements (for example they sometimes list 3 "serial ports", but it appears that only one of the three is RS232, for example, and don't mention what the other two are). The #1 constraint is cost, #2 is size.
Can anyone help me with this? This little task has left me thinking I should have gone for EE and not CS :-).
EDIT: A bit of background: This is a system currently in production, but the original programmer passed away, and the current hardware manufacturer cannot find hardware to run the (currently) DOS system, so I need to reimplement this in a modern platform. I can only change the programming and the motherboard hardware.
I suggest buying a cheap Atom Mini-ITX board, some of which come with multi - 4+ RS232 ports.
But with Serial->USB converters, this isn't really an issue. Just get an Atom. And if you have code, port your software to Linux.
Here is a link to a Jetway Mini-Itx board, and a link to a 4 port RS232 expansion module for it. ~$170 total, some extra for memory, a disk, and a case and PSU. $250-$300 total.
Now here is an Intel Atom Board at $69 to which you could add flash storage instead of drives, and USB-serial converters for any data collection you need to do.
PC104 has a lot of value in maximizing the space used in 19" or 23" rackmount configurations - if you're not in that space, PC104 is a waste of your time and money, IMHO.
The BeagleBoard should have everything you need for $200 or so - it can run Linux so use whatever programming language you like.
A 'modern' system will run DOS so long as it is x86, I suggest that you look at an industrial PC board from a supplier such as Advantech, your existing system may well run unchanged if it adheres to PC/DOS/BIOS standards.
That said if your original system runs on DOS, the chances are that you do not need the horsepower of a modern x86 system, and can save money by using a microcontroller board using something fairly ubiquitous such as an ARM. Also if DOS was the OS, then you most likely do not need an OS at all, and could develop the system "bare-metal". The resources necessary just to support Linux are probably far greater than your existing application and OS together, and for little or no benefit unless you intend on extending the capability of the system considerably.
There are a number of resources available (free and commercial) for implementing a file system and USB on a bare-metal system or a system using a simple real-time kernel such as FreeRTOS or eCOS which have far smaller footprints than Linux.
The Windows embedded site ( http://www.microsoft.com/windowsembedded/en-us/default.mspx )
has a lot of resources and links to hardware partners, distributors and development kits. There's even a "Spark" incubation project ( http://www.microsoft.com/windowsembedded/en-us/community/spark/default.mspx )
What's also really nice about using windows ce is that it now supports Silverlight as a development environment.
I've used the jetway boards / daughter cards that Chris mentioned with success for various projects from embedded control, my home router, my HTPC front end.
You didn't mention what the actual application was but if you need something more industrial due to temperature or moisture constraints i've found http://www.logicsupply.com/ to be a good resource for mini-itx systems that can take a beating.
A tip for these board is that given your minimal storage requirements, don't use a hard drive. Use an IDE adapter for a compact flash card as the system storage or an SD card. No moving parts is usually a big plus in these applications. They also usually offer models with DC power input so you can use a laptop like or wall wart external supply which minimizes its final size.
This http://www.fit-pc.com/web/ is another option in the very small atom PC market, you'd likely need to use some USB converters to get to your desired connectivity.
The beagle board Paul mentioned is also a good choice, there are daughter cards for that as well that will add whatever ports you need and it has an on board SD card reader for whatever storage you need. This is also a substantially lower power option vs the atom systems.
There are a ton of single board computers that would fit your needs. When searching you'll normally find that they don't keep many interface connectors on the processor board itself but rather you need to look at the stackable daughter cards they offer which would provide whatever connections you need (RS-232, etc.). This is often why you see just "serial port" in the description as the final physical layer for the serial port will be defined on the daughter card.
There are a ton of arm based development boards you could also use, to many to list, these are similar to the beagle board. Googling for "System on module" is a good way to find many options. These again are usually a module with the processor/ram/flash on 1 card and then offer various carrier boards which the module plugs into which will provide the various forms of connectivity you need.
In terms of development, the atom boards will likely be the easiest if your more familiar with x86 development. ARM is strongly supported under linux though so there is little difficulty in getting these up and running.
Personally i would avoid windows for a headless design like your discussing, i rarely see a windows based embedded device that isn't just bad.
Take at look at one of the boards in the Arduino line, in particular the Arduino Mega. Very flexible boards at a low cost, and the Mega has enough I/O ports to do what you need it to do. There is no on-chip modem, but you can connect to something like a Phillips PCD3312C over the I2C connector or you can find an Arduino add-on board (called a "shield") to give you modem functionality (or Bluetooth, ethernet, etc etc). Also, these are very easy to connect to an external memory device (like a flash drive or an SD card) so you should have plenty of storage space.
For something more PC-like, look for an existing device that is powered by a VIA EPIA board. There are lot of devices out there that use these (set-top boxes, edge routers, network security devices etc) that you can buy and re-program. For example, I found a device that was supposed to be a network security device. It came with the EPIA board, RAM, a hard drive, and a power supply. All I had to do was format the hard drive, install Linux (Debian had all necessary drivers already included), and I had a complete mini-computer ready to go. It only cost me around $45 too (bought brand new, unopened on ebay).
Update: The particular device I found was an EdgeSecure i10 from Ingrian Networks.
When I hear that, I always think about an mobile device. But why is the hardware "embedded" there? Isn't the whole device the hardware? Why is a personal computer no embedded hardware system?
In today's world embedded simply refers to a system with one or more of the following traits:
Single purpose (ie, not a general purpose computer, like your desktop)
Firmware rather than software - still software, but not as easily updated (flash, etc)
Hardware and software are designed together as a unit
Different, perhaps more rigorous testing as software updates are not desired
Real time computing
Memory integrated on the CPU
Microcontroller rather than microprocessor
Expected high reliability (you shouldn't have to reboot your dishwasher or microwave)
If it runs a program, but doesn't look like a computer, it's an embedded system.
That's my standard answer for friends and family. There's too many different types of embedded systems to get more specific.
I worked in the "embedded" area for a while and we considered anything that we had to write custom code for the hardware to be embedded.
If you have to work around the memory structure, write custom device drivers and anything that sits "directly on the metal" is generally "embedded".
If you're debugging it via a serial port - it's embedded.
It is called "embedded" because the computer is embedded as part of a larger device.
There is a very wide range of embedded systems.
At the low end are 8-pin PICs, for example there is a 12F629 in these diode lights. These costs cents and have very little memory.
The NXT by LEGO contains two controllers, a relatively big AT91SAM7S256 with a 32-bit ARM core, 256KB of flash ROM and 64KB of RAM, and a smaller 8-bit ATmega48 with 4KB of flash.
Currently I'm working on embedded systems for trains, these typically have a PowerPC with some hundreds of MHz clock, on the order of a hundred MB of RAM, run VxWorks or Linux and are connected by Ethernet.
I think there are still more powerful embedded systems for telecommunications, but I haven't worked on these.
As per Wikipedia:
An embedded system is a
special-purpose computer system designed to perform one or a few
dedicated functions, often with
real-time computing constraints. It is
usually embedded as part of a complete
device including hardware and
mechanical parts. In contrast, a
general-purpose computer, such as a
personal computer, can do many
different tasks depending on
programming.
Embedded systems are designed to do some specific task, rather than be a
general-purpose computer for multiple
tasks. Some also have real-time
performance constraints that must be
met, for reasons such as safety and
usability; others may have low or no
performance requirements, allowing the
system hardware to be simplified to
reduce costs.
Embedded systems are not always standalone devices. Many embedded
systems consist of small, computerized
parts within a larger device that
serves a more general purpose. For
example, the Gibson Robot Guitar
features an embedded system for tuning
the strings, but the overall purpose
of the Robot Guitar is, of course, to
play music.[2] Similarly, an embedded
system in an automobile provides a
specific function as a subsystem of
the car itself.
The program instructions written for embedded systems are referred to as
firmware, and are stored in read-only
memory or Flash memory chips. They run
with limited computer hardware
resources: little memory, small or
non-existent keyboard and/or screen.
From personal experience, if it's "headless" (i.e. doesn't have an output device like a VDU and relies on something like LED's), if there is a serial port used mainly for debugging and logging and if you often use a logic analyser for debugging, it's embedded.
"Embedded" has become a very diverse term.
I've seen and worked on designs that:
Simply toggled discrete I/O (including LEDs) at fixed intervals
Drivers for hardware solutions (e.g. webcams, wireless com)
Acted as communications translators for board-level I/O (SPI<->I2C<->Rs232<->USB)
[ insert multitude of appliances here ]
Human-controlled electronics (calculator-esque, phone-esque)
System level devices to coordinate actions of other devices.
I also like Dour-High-Arch's comment above:
"Another important difference is that embedded apps may run for years without intervention..."
"Embedded system" is a very broad term and I don't think that it is easy to have a single definition. The word "embedded" actually refers to an industry and not to a "hardware system". The description of embedded systems has changed over the years and it is definitely going to change in the future too.
In early days one would say the embedded systems were only programmed in assembly, but now C is common place and perhaps in the future other languages are used as well. CPUs are getting bigger and bigger, external memories are used all the time and they are many devices considered to be embedded that are not dedicated to a single task, applications can be added to them and the software is easily updated. Watches, gadgets, house appliances, automotive devices, PLCs, motor controllers, weather stations, system monitoring devices are all considered embedded. It is difficult to singe define them all.
I remember reading some time ago that there were cpu cards for systems to add additional processing power to do mass parallelization. Anyone have any experience on this and any resources to get looking into the hardware and software aspects of the project? Is this technology inferior to a traditional cluster? Is it more power conscious?
There are two cool options. one is the use of GPU's as Mitch mentions. The other is to get a PS/3, which has a multicore Cell processor.
You can also set up multiple inexpensive motherboard PCs and run Linux and Beowulf.
GPGPU is probably the most practical option for an enthusiast. However, DSPs are another option, such as those made by Texas Instruments, Freescale, Analog Devices, and NXP Semiconductors. Granted, most of those are probably targeted more towards industrial users, but you might look into the Storm-1 line of DSPs, some of which are supposed to go for as low as $60 a piece.
Another option for data parallelism are Physics Processing Units like the Nvidia (formerly Ageia) PhysX. The most obvious use of these coprocessors are for games, but they're also used for scientific modeling, cryptography, and other vector processing applications.
ClearSpeed Attached Processors are another possibility. These are basically SIMD co-processors designed for HPC applications, so they might be out of your price range, but I'm just guessing here.
All of these suggestions are based around data parallelism since I think that's the area with the most untapped potential. A lot of currently CPU-intensive applications could be performed much faster at much lower clock rates (and using less power) by simply taking advantage of vector processing and more specialized SIMD instruction sets.
Really, most computer users don't need more than an Intel Atom processor for the majority of their casual computing needs: e-mail, browsing the web, and playing music/video. And for the other 10% of computing tasks that actually do require lots of processing power, a general-purpose scalar processor typically isn't the best tool for the job anyway.
Even most people who do have serious processing needs only need it for a narrow range of applications; a physicist doesn't need a PC capable of playing the latest FPS; a sound engineer doesn't need to do scientific modeling or perform statistical analysis; and a graphic designer doesn't need to do digital signal processing. Domain-specific vector processors with highly specialized instruction sets (like modern GPUs for gaming) would be able to handle these tasks much more efficiently than a high power general-purpose CPU.
Cluster computing is no doubt very useful for a lot of high end industrial applications like nuclear research, but I think vector processing has much more practical uses for the average person.
Have you looked at the various GPU Computing options. Nvidia (and probably others) are offering personal supercomputers based around utilising the power of graphics cards.
OpenCL - is an industry wide standard for doing HPC computing across different vendors and processor types, single-core, multi-core, graphics cards, cell, etc... see http://en.wikipedia.org/wiki/OpenCL.
The idea is that using a simple code base you can use all spare processing capacity on the machine regardless of type of processor.
Apple has implemented this standard in its next version Mac OS X. There will also be offerings from nVIDIA, ATI, Intel etc.
Mercury Computing offers a Cell Accelerator Board, it's a PCIe card that has a Cell processor, and runs Yellow Dog Linux, or Mercury's flavor of YDL. Fixstars offers a more powerful Cell PCIe board called the GigaAccel. I called up Mercury, they said their board is about $5000 USD, without software. I'd guess the GigaAccel is up to twice as expensive.
I found one of the Mercury boards used, but it didn't come with a power cable, so I haven't been able to use it yet, sadly.