So, I know Linux kernel is quite "heavy" when considering lower scale embedded systems, but currently but we're a 2 man team trying to see how to create our own embedded system.
I'm the one in charge of all software (the other guy is a HW guy), and thus I would like to re-use existing libraries and frameworks as much as possible, and I would like to bounce off some ideas with gurus around here.
I am fairly comfortable in Linux, but the booting and initialization process is new to me, and I need to dive in to that soon enough. Any book recommendations are welcome as well!
I haven't designed any embedded systems before.. Only own some ARM dev boards (beagleboard and raspberry pi).
Current I have prototype of the software running on beagleboard already, and now we're thinking how to minimize the cost, and to create something our own..
It's a system connected to the internet, and I need to run a tiny web server with some scripting support. Performance wise I don't think it needs to be too powerful.
I would like to minimize all bootloader etc work, since I'm a one man SW team, and just concentrate on the application itself.
Of course I understand that I need to configure our kernel for this, but this is indeed why I thought selecting some SoC would be good, since they usually have some linux and bootloaders ready..
First I thought that Cirrus EP9301 would be perfect, since it seems to be a good package, and not very expensive.. But it seems that it's already in end-of-life, and also support for this is very bad (people on the cirrus forums constantly complain about it).
Are there some good choices for this kind of project, which would enable us "easily" to get linux kernel up and running, with still maintaining some kind of decent BOM (hopefully 20USD or so) ?
Your hardware guy should already know this, but go with an existing reference design. Take the raspberry pi, the beagleboard/bone, open-rd, or any number of other existing systems and clone the part you need. As a result the linux porting will be a matter of removing what you are not using from the reference design instead of adding new stuff and hoping it works. If you go with flat pack parts you can do the work in your garage, if you go with bgas you need the equipment for that or pay someone to do it. (can you tell yet that I hate bgas?).
Is linux a requirement, if not that opens the door to a lot more devices using freertos or chibios or a number of other solutions. the stm32f4 discovery board for example is $20, uses what can barely be called a microcontroller for all the features it has (cortex-m4). Supposedly possible to run uclinux on a cortex-m, but definitely possible to run any number of rtoses and have an ip stack, etc. stellaris (ti.com) has a number of eval boards, one/some with ethernet already (use as a reference design). You can also take the wiznet approach (or a spi ethernet) and use any microcontroller (puts you into the avr/msp430 level and price range). Bang for buck the cortex-m's are good, arm based so comfortable to work with, etc.
Using linux if you are already not an experienced at porting to an embedded platform, and dont want to learn that on this go around, I would definitely go with a clone of an existing design, leverage as much as you can from a project with folks that are experienced at porting linux to a platform. If need be take an existing board (beagle/raspi/openrd) and go through the motions of porting to the platform with the cheat sheet of having access to an existing port, see if you cant get uboot ported and linux booting, etc. (dont really need uboot at all, that is possibly an unnecessary complication, just get dram up and pass the atags, etc to linux and just branch to it, pretty easy to launch linux from bare metal).
You could probably do worse than taking the Broadcom BCM2835 - used on the Raspberry Pi - as your starting point - especially if you want to avoid kernel and boot-loader work and a source of reference schematics. If this proves too expensive, check out other devices in the Broadcom range.
A few bits of advice
You probably want some flash rather than a MMC card interface for production use. eMMC is an option. NAND flash is a nightmare due to rapid component obsolescence and the need to get own and dirty with the MTD drivers.
USB Ethernet will be easier to integrate than a controller hanging off a general purpose bus, but won't perform as well. SmSC seems to be popular source for either
You could also have a look at the work that Olimex is doing with their linux boards. Perhaps even order a som and then combine it with other external components.
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I have a Samsung TV with connected via optical output to my DTS sound system.TV has ARM CPU and an embedded linux operating system. It comes with an embedded media player.But internal media player doesn't pass DTS audio to my sound system. it only passes-though AC3 and other formats. I want to hack TV's firmware to pass-though DTS audio to my sound system.
What are the books, learning resources etc. to start this kind of hobby project ? I have never programmed on embedded platform. What should I know before the start ? For example Should I know audio programming, electronics, Linux Kernel, C Programming ? Any recommendation would be helpful.
Actually there is a whole dedicated sourceforge project related to firmware hacking on Samsung TVs called SamyGO. But When I asked one of main firmware hacker in this site, I didn't get a reply from him. So I thougth someone here can answer to my question.Thanks..
UPDATE :
How much electronics knowledge should I have for this kind of job ? (I have a C.S degree and basic knowledge about electronics, logic design etc.). Should I be a linux kernel or C expert ?
Actually I have always wondered how embedded device hackers like George Hotz gain this kind of knowledge.Because it is a closed system, they don't have any documentation, how can they do this? Do they learn it from school?(I don't think so). If they do, What do they study? Which books do they use? If they don't, how ?
I came across this excellent blog post on Reverse engineering firmware for Linksys router,
http://www.devttys0.com/2011/05/reverse-engineering-firmware-linksys-wag120n/
It explains in detail how to reverse engineer the firmware, get to the file system in clear steps. If you can follow through the steps, you would get a really good insight into what it takes to hack a firmware.
I don't think you require lot of electronics knowledge to hack a firmware, basic 101 level knowledge would suffice. If you understand basic OS and systems in general then you should be able to work your way through.
Hacking an undocumented system is nowhere a trivial task. You definitively should learn C and practice embedded programming and a good knowledge about electronics will help a lot (you'll have to look at the circuit and guess how it works, if you can't find any docs on google).
My advice is: get some (documented) ARM board to start hacking on (beagleboard/pandaboard comes to mind). You'll learn a lot about Linux, C, Kernel development and even electronics if you want to.
Trying to dive directly on a TV system will probably be very frustrating for you.
UPDATE:
At the electronics side, you don't need to be an electronic engineer. Study a lot of digital electronics and understand how CPU's, buses and commom peripherals work. Most of the time you can look at any chip code and search for it datasheet, but sometimes they're designed specially for one device, or have no identification at all. In this case, you'll need a logic analyzer to reverse engineer it and try to understand how to "talk" to it.
You can learn CS and electronics from books, but real reverse engineering can only be learnt by experience (of course, learning how others do things helps a lot).
Go on and open devices you find interesting, try to understand how they work and change things on it. You'll for sure burn some of them (begin with the cheaper ones), but it's the best way to learn how to hack devices.
Just take care to not die while messing with high voltage devices (and LCD TV do have some HV parts)
Suitable development boards to consider, with very active communities, i.e. easy to get help if you are stuck :-)
http://www.arduino.cc/
http://beagleboard.org/
Start with them to learn about embedded systems, before you move on the more difficult tasks
Yes,C language knowledge is important.
First try and learn Raspberry Pi then jump into Adruino.
You could find so many communities for these in facebook and google plus join and involve yourself.
Then you can learn so many hacks
Title basically surmises the question, but just to clarify. What language or languages are used for programming remotes for multimedia setups like home theater systems? Is it a scripting language? Are there SDKs?
Here's an example I'm pondering. Someone wants a high end theater installed. They get A/V consultants to come in and have the remote do something special, like dim the lights, turn the TV on in 5 minutes and switch inputs. All of this seems custom to the client. Does the A/V consultant go back to the shop, tell his requirements to the programmer and the programmer rights some assembly to make it happen?
You can buy programmable remotes which can learn some pretty advanced control sequences. Take a look at the links in this Coding Horror post which recommends Logitech harmony remotes
The language is most likely Assembly (maybe C if your lucky). Don't expect to see a remote that uses a scripting language. Scripting Languages are great for writing everyday programs but when it comes to writing software to interface to hardware you run into a wall. Scripting Languages try to protect you from low-level stuff (like pointers). When writing software for a remote you need low-level stuff.
I wouldn't expect to see anything like the .NET Mircoframework for the remote (unless the remote was made specially for that).
A remote is almost certainly perceived of as a device, not a programming platform. This means that the programming will be done in a way that is cheapest to fit into the device, since the cost of getting the programming done is much less than the cost of giving every device additional computational power. The remote is almost certainly not capable of being reprogrammed in any other way than swapping out a chip or larger component.
There are software development kits for programming chips used as microcontrollers, although they're not likely to have special features for remotes and the like. They're likely to come from the chip vendor, although I've seen third-party kits for sale. They may not be cheap: when you're going to ship a half-million units you're probably doing everything you can to get production costs down and not caring as much about the fixed costs.
I am working on SBC(Single Board Computer) board with Red Hat Linux, which is being used to get information from many routers and process packets.
Can this Gateway be called an "Embedded Linux based" product?
I would call it embedded if its purpose has been shifted from a general purpose computer to a device or appliance that has a specific task. Further, customization for that specific task should probably remove/disable/mitigate some other general purpose functionality (e.g. running it headless, disabling/removing X or general use tools/services in order to further enable the device to do its job.)
Basically look at the device and discern whether it appears as "a computer running linux" or "an appliance which completes a specific task USING linux."
See this question regarding which systems can be described as embedded. In industry terms, I would say that a headless Linux device is said to be "embedded".
I don't agree that it needs to be headless to be considered embedded. For example, mobile phones are considered embedded but they've got video, i/o and what nots. Personally, I think that there is no 'clear' line for embedded. But generally, when you are working with minimal resources (e.g. minimal RAM) and performing very specific functions (i.e. not general purpose) then it's more embedded.
Short answer: Yes
From 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 control
many of the common devices in use
today.
While I think your device isn't embedded on another device, I see that has little functions and is not a general purpose computer.
Also, as Shashikiran says, SBCs are usually called embedded systems.
PC-104 drived me crazy some years ago...
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Now I'm sure we're all well aware of the relative merits of Linux vs Windows Desktop. However I've heard much less about the world of embedded development. I'm mainly interested in solutions for industry and am therefore uninterested about the IPhone or Android and more interested in these two OSes.
What are the relative trade-offs between the two platforms in the embedded world? If you were considering building a box for a specific project with custom hardware, a partially customised OS and a custom app then which would you choose and why?
I would assume that Windows CE wins on tools and Linux wins on both cost and possibly performance. However this is just utter speculation. Does anyone have any facts or experience of the two?
I worked for several years at a company that provided both CE and Linux for all of their hardware, so I'm fairly familiar with both sides of this equation.
Tools: Windows CE tools certainly are better than those provided by Linux, though the linux tools are certainly getting better.
Performance: Windows CE is real-time. Linux is not. The linux kernel is not designed for determinism at all. There are extensions that you can add to get sort-of real time, but CE beats it.
Cost: This is an area of great misunderstanding. My general experience is that CE is lower cost out of the box ($1k for Platform Builder and as low as $3 per device for a shipping runtime. "What?" you ask? "Linux is free." Well, not really so much, especially in the embedded arena. Yes, there are free distributions like Debian. But there are plenty of pieces that you might need that aren't in that free category. UI frameworks like QT, Java runtimes and media codecs just as a start. Also, most Linux distributions with a commercially-backed support system (e.g. MontaVista) are far from free.
Source Availability: Linux proponents may like to say that CE is a bad choice due to lack of source code. All I can say is that in over a decade of working with CE, half of which spent doing custom kernel and driver work for custom boards, I've only ever had need for source that didn't ship with CE (they ship a vast majority of it) once. I like having source too, but Microsoft provides support, so in the rare case you might think you need that source, you can get them to fix the problem (the one time we needed source, Microsoft provided a fix, and for free - which is their model under CE.
Does this mean that CE wins every time? No. I wouldn't suggest that at all. If you are a Linux shop and you have lots of Linux experience and code assets, you'd be foolish to run out and go CE. However, if you're coming into it from scratch CE usually has a lower TCO. Developers with Win32/C# experience are more prevalent and consequently less expensive. You also get a lot more "in the box" with CE than most other distributions, meaning faster time to market if you don't already have these things done in-house already.
I'll speak for the Linux side, at least for the category of software I'm familiar with (which is RF data collection equipment). Or industrial apps vs. consumer apps.
Windows CE (and its associated tools) IMH fairly recent E) is strongly biased to creating a "Windows Experience" on a small screen. The user input mode emphasizes mouse-like actions. Logons, application selection, etc. all try to be as similar to standard Windows as possible.
If a user is driving a lift truck, or filling a picking cart, or moving material from one place to another, there's a problem.
And it's a moving target - particularly on the .NET side. The Compact .NET runtime is seriously handicapped, and important libraries (like networking, data handling, and UI) are incomplete and versions too often deprecate the previous version. . CE seems to be the stepchild in the Windows family (possibly because there's not a lot of active competition selling to the hardware integrators.)
A nice stable rows-and-columns Linux console is a pretty handy context for many (in my experience most) high-use apps on a dinky screen.
Not much good for games on your cell-phone or Zune, though.
NOTE:
I think ctacke probably speaks accurately for the hardware integrator's side. I'm more aligned with the players further down the pipe - software integrators and users.
Choice is often made largely on perception and culture, rather than concrete data. And, making a choice based on concrete data is difficult when you consider the complexity of a modern OS, all the issues associated with porting it to custom hardware, and unknown future requirements. Even from an application perspective, things change over the life of a project. Requirements come and go. You find yourself doing things you never thought you would, especially if they are possible. The ubiquitous USB and network ports open a lot of possibilities -- for example adding Cell modem support or printer support. Flash based storage makes in-field software updates the standard mode of operation. And in the end, each solution has its strengths and weaknesses -- there is no magic bullet that is the best in all cases.
When considering Embedded Linux development, I often use the iceberg analogy; what you see going into a project is the part above the water. These are the pieces your application interacts with, drivers you need to customize, the part you understand. The other 90% is under water, and herein lies a great deal of variability. Quality issues with drivers or not being able to find a driver for something you may want to support in the future can easily swamp known parts of the project. There are very few people who have a lot of experience with both WinCE and Linux solutions, hence the tendency to go with what is comfortable (or what managers are comfortable with), or what we have experience with. Below are thoughts on a number of aspects to consider:
SYSTEM SOFTWARE DEVELOPMENT
Questions in this realm include CPU support, driver quality, in field software updates, filesystem support, driver availability, etc. One of the changes that has happened in the past two years, is CPU vendors are now porting Linux to their new chips as the first OS. Before, the OS porting was typically done by Linux software companies such as MontaVista, or community efforts. As a result, the Linux kernel now supports most mainstream embedded cpus with few additional patches. This is radically different than the situation 5 years ago. Because many people are using the same source code, issues get fixed, and often are contributed back to the mainstream source. With WinCE, the BSP/driver support tends to be more of a reference implementation, and then OEM/users take it, fix any issues, and that is where the fixes tend to stay.
From a system perspective, it is very important to consider flexibility for future needs. Just because it is not a requirement now does not mean it will not be a requirement in the future. Obtaining driver support for a peripheral may be nearly impossible, or be too large an effort to make it practical.
Most people give very little thought to the build system, or never look much beyond the thought that "if there is a nice gui wrapped around the tool, it must be easy". OpenEmbedded is very popular way to build embedded Linux products, and has recently been endorsed as the technology base of MontaVista's Linux 6 product, and is generally considered "hard to use" by new users. While WinCE build tools look simpler on the surface (the 10% above water), you still have the problem of what happens when I need to customize something, implement complex features such as software updates, etc. To build a production system with production grade features, you still need someone on your team who understands the OS and can work at the detail level of both the operating system, and the build system. With either WinCE or Embedded Linux, this generally means companies either need to have experienced developers in house, or hire experts to do portions of the system software development. System software development is not the same as application development, and is generally not something you want to take on with no experience unless you have a lot of time. It is quite common for companies to hire expert help for the first couple projects, and then do follow-on projects in-house. Another feature to consider is parallel build support. With quad core workstations becoming the standard, is it a big deal that a full build can be done in 1.2 hours versus 8? How flexible is the build system at pulling and building source code from various sources such as diverse revision control systems, etc.
Embedded processors are becoming increasingly complex. It is no longer good enough to just have the cpu running. If you consider the OMAP3 cpu family from TI, then you have to ask the following questions: are there libraries available for the 3D acceleration engine, and can I even get them without being committing to millions of units per year? Is there support for the DSP bridge? What is the cost of all this? On a recent project I was involved in, a basic WinCE BSP for the Atmel AT91SAM9260 cost $7000. In terms of developer time, this is not much, but you have to also consider the on-going costs of maintenance, upgrading to new versions of the operating system, etc.
APPLICATION DEVELOPMENT
Both Embedded Linux and WinCE support a range of application libraries and programming languages. C and C++ are well supported. Most business type applications are moving to C# in the WinCE world. Linux has Mono, which provides extensive support for .NET technologies and runs very well in embedded Linux systems. There are numerous Java development environments available for Embedded Linux. One area where you do run into differences is graphics libraries. Generally the Microsoft graphical APIs are not well supported on Linux, so if you have a large application team that are die-hard windows GUI programmers, then perhaps WinCE makes sense. However, there are many options for GUI toolkits that run on both Windows PCs and Embedded Linux devices. Some examples include GTK+, Qt, wxWidgets, etc. The Gimp is an example of a GTK+ application that runs on windows, plus there are many others. The are C# bindings to GTK+ and Qt. Another feature that seems to be coming on strong in the WinCE space is the Windows Communication Foundation (WCF). But again, there are projects to bring WCF to Mono, depending what portions you need. Embedded Linux support for scripting languages like Python is very good, and Python runs very well on 200MHz ARM processors.
There is often the perception that WinCE is realtime, and Linux is not. Linux realtime support is decent in the stock kernels with the PREEMPT option, and real-time support is excellent with the addition of a relatively small real-time patch. You can easily attain sub millisecond timing with Linux. This is something that has changed in the past couple years with the merging of real-time functionality into the stock kernel.
DEVELOPMENT FLOW
In a productive environment, most advanced embedded applications are developed and debugged on a PC, not the target hardware. Even in setups where remote debugging on a target system works well, debugging an application on workstation works better. So the fact that one solution has nice on-target debugging, where the other does not is not really relevant. For data centric systems, it is common to have simulation modes where the application can be tested without connection to real I/O. With both Linux and WinCE applications, application programing for an embedded device is similar to programming for a PC. Embedded Linux takes this a step further. Because embedded Linux technology is the same as desktop, and server Linux technology, almost everything developed for desktop/server (including system software) is available for embedded for free. This means very complete driver support (see USB cell modem and printer examples above), robust file system support, memory management, etc. The breadth of options for Linux is astounding, but some may consider this a negative point, and would prefer a more integrated solution like Windows CE where everything comes from one place. There is a loss of flexibility, but in some cases, the tradeoff might be worth it. For an example of the number of packages that can be build for Embedded Linux systems using Openembedded, see.
GUI TRENDS
It is important to consider trends for embedded devices with small displays being driven by Cell Phones (iPhone, Palm Pre, etc). Standard GUI widgets that are common in desktop systems (dialog boxes, check boxes, pull down lists, etc) do not cut it for modern embedded systems. So, it will be important to consider support for 3D effects, and widget libraries designed to be used by touch screen devices. The Clutter library is an example of this type of support.
REMOTE SUPPORT
Going back to the issue of debugging tools, most people stop at the scenario where the device is setting next to a workstation in the lab. But what about when you need to troubleshoot a device that is being beta-tested half-way around the world? That is where a command-line debugger like Gdb is an advantage, and not a disadvantage. And how do you connect to the device if you don't have support for cell modems in New Zealand, or an efficient connection mechanism like ssh for shell access and transferring files?
SUMMARY
Selecting any advanced technology is not a simple task, and is fairly difficult to do even with experience. So it is important to be asking the right questions, and looking at the decision from many angles. Hopefully this article can help in that.
I have worked in projects that involved customizing the software of an OEM board and I wouldn't say that Linux is cheaper. When buying a board you also need to buy the SDK. You still need to pay even for the Linux version. Some manufacturers offer both Windows CE and Linux solutions for their boards and there isn't a price difference. For Windows CE you also need the Platform Builder and pay for the licenses, but it is easier to go without support.
Another important issue is if you are building a User Interface or a headless device. For devices that require an LCD screen and human interaction is much easier to go with Windows CE. If on the other hand you are building a headless device, Linux may be a sounder option - especially if network protocols are involved. I believe that Linux implementations are more reliable and easier to tweak.
With Linux you are never on you own and you are never dependent on one single entity to provide permissions. There are many support options and you have the freedom to choose your support options for any part of the system through many competing sources.
With Windows CE you must adhere to the license and restrictions as set forth in the complex license agreements that must be agreed to. Get a lawyer. With windows CE you have only one proprietary source for OS support and you will proceed only as they see fit to support and provide what you need. You may not agree with their position, but will not have any recourse but to bend to what they prescribe. The costs of incremental components, modules, development kits, licensing, and support tend to pile up with proprietary platforms. In the longer term, what happens when the vendor no longer desires to support the platform and you do not have the rights to support and distribute it yourself? What happens when the vendor moves to newer technology and wants you to move along with them even though you may not be ready to make the move? $$$
Our experience with Windows solutions in general is that they tend to become more expensive over time. What was originally considered lowest TCO gravitates quickly towards and solution that is encumbered and costly to maintain and support. Licenses have to be re-negotiated over time and the new technologies, often unneeded, are forced into the picture at the whim of the provider for the sake of THEIR business needs. On top of that, the license agreements are CONTINUALLY changing--get a lawyer.
With Linux you have the freedom to provide in-house support and expertise without being encumbered against distributing the solution as you need. You also have the freedom to continue to use and support technology that original providers no longer want to support. Having the source code and the RIGHTs to do with it what you want (GPL, LGPL) is a powerful attractor when it comes to business continuity and containing costs while providing access to the very latest technologies or technologies that fit your needs.
I have developed network drivers that work both on RT Linux (to be more specific, Linux preemptive kernel with RT patch) and Windows CE. My experience was windows CE was more stable in terms of real-time response. Frame timings also showed that windows CE had less jitter.
On RT Linux, we had all sorts of problems. For example, when user moved the mouse; our frames were being delayed. Guess what, certain variants of x-windows disable interrupts. You may also feel that you are safer on console screen only. If you have VGA frame buffers enabled, you are doomed again. We had only one problem with windows CE in terms of jitter again. The problem happened when the USB controller was set to an incorrect mode in the BIOS and windows CE was using lots of time for polling.
To be honest, windows CE had more support. On Linux, you are on your own. You have to read every possible mailing list to understand what problems you may hve.
a partially customised OS
Is much easier to achieve if the OS is open source (and you have the expertise).
Android is a good option for some embedded systems.(it's linux based)
You have many experts that are able to develop on this system.
You have access to many libraries in java or C.
but it uses lot of memory and energy.
What we often forget with paid / licenced software is that you have to deal with licenses. It takes time and energy! Then you have to track if you pay it correctly. It involves many different people with different skills and it costs in decision.
This cost is often not included in the studies that show that open-source/free is more expensive than paid software.
With "free software" it's way easier to deal with licenses and you spend less time on dealing with these issues. Personally I prefer to avoid unnecessary communications with your legal / financing team every time you change some pieces of the software.