Feature Embedded Technology
A serious look at the Raspberry Pi
Rory Dear at embedded systems specialist DSL asks whether the hype around the Raspberry Pi is clouding judgement when it comes to embedded computing
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n 2011 a new computing platform hit the headlines. With a catchy name, the Raspberry Pi, and born out of the University of Cambridge that had been responsible for the BBC Micro 30 years earlier, it was not surprising that it caused a bit of a stir. How could a fully functional ‘PC’ be miniaturised thought an admiring public and even the more informed embedded community was impressed with the miniaturised price tag. Designed for education to put the fun back into learning computing, here was a product that could solve one of the biggest questions in our industry: how do we inspire our children to become engineers? Could the Raspberry Pi do what the BBC Micro had achieved for an earlier generation? Unfortunately, as with all innovative technologies, there are always those keen to push it into other areas. A good example would be the use of Teflon on frying pans but there are many that have not been so successful. Such innovation has been the corner- stone of mankind’s technological pro- gression but can also be very dangerous when technology is driven into an area it was never designed for - hydrogen in airships anyone? The danger allured to here is that of employing the Raspberry PI into a real life embedded or industrial computing application. The attraction of the low price tag and increased profits by supplying products at a fraction of a cost of your competitors is compelling. While the device is indeed a techno- logical achievement, it was designed to educate on, not to integrate into embedded applications. Developers considering transferring this hardware into unknown territory should care- fully consider the following.
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Full documentation is not available for developers, nor is it likely to be as it is heavily under protection from its designers. This is in contrast to a typical embedded platform where a plethora of supporting documentation is made available to the developer, guiding them smoothly through their projects. While the ability to play 1080p video via HDMI may instantly create a percep- tion of blistering performance, in reality this is handled off-chip and the CPU performance is the equivalent of a creaky 300MHz Pentium 2. This is important as few embedded/industrial applications have a call for much graph- ical grunt, if they use graphics at all. Using an SD card to house any kind of Operating System (OS) has its pit- falls; but it is the only option on a Raspberry Pi. An SD card’s maximum
The Raspberry Pi, a credit-card-sized single-board computer
developed in the UK by the Raspberry Pi Foundation
new LCD displays have HDMI input. But in the embedded sector, if a display is required then a ruggedised industrial display is unlikely to have HDMI, especially as they tend to be much smaller, down to 5.7”. The defining feature of most embed- ded single-board-computers (SBCs) is their wide temperature range, allowing usage in the most extreme environments. Typically, you’d expect to see a stan- dard temperature range of -20°c to 70°c; though more often than not the full industrial temperature range of - 40°c to 85°c. However, the Raspberry Pi’s components can only offer 0 to 70°c and if you read the manufac- turer’s FAQ they do not qualify the board itself to any extreme.
“The Raspberry Pi is a fantastic product, innovative and to which we will probably owe a substantial debt for inspiring and educating the next generation of embedded developers to wonderful things with future technologies. But please be careful – it is not a panacea for embedded computing solutions”
read/write speeds are a fraction of typi- cal storage mediums, similarly to total read/write cycles; so little longevity is offered to the developer who’s used to specifying systems to reside in the field for up to ten years without servicing. Interestingly, the device supports only RCA or HDMI. The argument that VGA is a dying format does hold some truth in the retail sector where most
Rory Dear is Technical Sales Manager at DSL
Other features embedded developers often take for granted including PXE Boot – the ability to boot directly from a server – aren’t supported; nor are high data transfer rates. The on board Ethernet interestingly is derived from the USB 2.0 port. This means that the Ethernet is restricted to 10/100 and the USB 2.0 cannot operate at full speed, as it is sharing the bandwidth. One interesting omission that many would struggle with in this sector is the absence of a Real Time Clock (RTC) or Hardware Watchdog. Furthermore, if one ponders its implementation for more complex equipment, the absence of any expansion capability beyond USB, which has its own drawbacks for such peripherals, is a cause for concern. No Windows based OS is supported, though many these days favour other Oss. The Windows environment offers the ultimate easy development plat- form and support for alternative OSs isn’t there yet. Taking a step back from the product itself momentarily; to be a valid solu- tion in the embedded market, there needs to be a continuity of supply. This takes many forms, including component control/obsolescence man- agement, strict version control on the BIOS, including the ability to create tailored custom BIOS’s; monitoring of future component availability; last time buys and far more than you could realise happens behind the scenes in the embedded industry.
DSL
www.dsl-ltd.co.uk Enter211
The combination of all the above pro- vides the confidence that what was pur- chased yesterday and integrated into a product at huge approval costs, will be available in 1, 2 or 5 years, or longer! In conclusion, the Raspberry Pi is a fantastic product, innovative and to which we will probably owe a substan- tial debt for inspiring and educating the next generation of embedded develop- ers to wonderful things with future technologies. But please be careful – it is not a panacea for embedded computing solutions.
SEPTEMBER 2013 Electronics
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