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3G data modem support is a core feature for the Real Time Passenger Information (RTPI) system designed by Bluewater Systems. The RTPI system is designed to collect and display information about the arrival times of buses at a particular point on the route. This information is provided by a unit on the buses which uses a GPS receiver and GPRS or other wireless communications to pass on positional information to a central server.

The choice of the 3G modem was dictated by another requirement: to use a cheaper GSM data modem as an assembly option. Bluewater decided to use the 3G embedded module MC8775 from Sierra Wireless, a low talk and low standby current modem which comes in PCI Express Mini Card form factor.

A Sierra Wireless MC8775 PCI Express Mini Card supports third generation (3G) digital cellular standards and it is globally certified. An MC8775 supports tri-band UMTS (HSDPA): 850/1900/2100 MHz, with forward link up to 3.6Mbps, and quad-band EDGE/GPRS/GSM: 850/900/1800/1900 MHz, with forward link up to 216 Kbps.

Although the data modem has a PCI Express Mini Card form factor, it does not support a PCI Express electrical interface. The host and USIM interfaces, as well as power supply for the 3G/GSM modules, are provided via a PCI Express Mini Card connector. The communication between the 3G data modem and the host (Snapper CL15 module) is provided via a USB 2.0 interface.

The PCI Express Mini Card form factor allows a simple downgrade path if it is cheaper, however, the same form factor GSM data modem designed by Bluewater Systems is desired. Another benefit of having the same form factor for 3G and GSM data modems is a smaller main board and a simple upgrade/downgrade path.

Traditionally, Linux-based applications have been built using GNU tools. Even today, Bluewater uses mostly GNU tools for application development, and always for the Linux kernel. For many years, Symbian used the GNU tools also. The rationale was that GNU tools are cheap and functional, and allow access to the widest possible developer base. However, this strategy broke with companies like Nokia and Ericsson. These companies were very happy with the idea of investing significant sums of money in better tools, and regarded the use of GNU as a missed opportunity. Symbian has therefore moved to a dual approach, with serious developers using RealView and casual developers using GNU. The benefits of RealView include a better compiler (faster and smaller code, more features, better documentation) and better debugging support. Microsoft has followed a different approach with Windows CE. Microsoft uses their own compiler with a number of vendor-specific extensions, and has little interest in encouraging other tools vendors. While this approach provides a highly functional, customised and integrated IDE, it forces customers to rely on the Microsoft ARM compiler, which is not exactly the best in the world. It seems that Linux is moving to the dual-tools approach used by Symbian. This will offer the best of both worlds - low cost GNU tools and highly functional RealView tools. To illustrate the potential benefits, recently we build a bayer filter algorithm with both GNU and RealView. This was for our Bigeye Camera project. The RealView-compiled code executed in about 400ms, versus 1.7 seconds for GNU, so RealView code was 4 times faster! This is an extreme case (other results show around a 10-20% benefit) but it does illustrate the potential benefits of using RealView. A few years ago ARM introduced a --gnu flag into their RealView compiler. Using this, Bluewater Systems has written an applications note for ARM on how to build application software and libraries for Linux using RealView. Today, building Linux applications using RealView requires a fair bit of fiddling, and detailed tools knowledge. But ARM is working on this, as evidenced by the better support in each release for the last several years. The goal seems to be to replace GNU entirely in the tools chain. Bluewater uses RealView tools for bringup, debugging Linux kernels and for debugging WinCE via EXDI2. Our engineers are itching to get a better development environment (particularly in debug) than that offered by GNU. We already have a foot in the water in this area. The next major step for us will be building our Snapper-targeted OpenEmbedded release using RealView. Time frames are unclear at the moment, but even with the current RealView tools we have been able to develop a script which handles translation of most common command-line arguments. The next 12 months should see a big leap forward in Linux tools support, and resulting software performance and engineer productivity. We will keep you posted on our progress. Availability of RealView tools looks like it's becoming a key benefit of using Linux.

When building embedded devices, one of the fundamental activities we do is coupling [suitable CPU A] with [selection of special-purpose peripherals B]. This gets you from having a feature-rich (but boring) SOM to a specialised device offered a wide range of sensory inputs and options. Being an embedded platform however, complexity, pin counts and space is at a premium - so instead of the more powerful IDE, PCI, PCIe or similar interfaces, words like I2C, SPI and RS232 tend to crop up a lot. In this note, I'd like to focus on I2C. I2C (Inter-Integraced Circuit,(http://en.wikipedia.org/wiki/I%C2%B2C), a.k.a. TWSI (Two-Wire Serial Interface), is a mostly-standardised interface using two control lines -- SDA (Serial Data) and SCL (Serial Clock) -- and in-band clocking. In practice, different I2C devices use very similar protocols -- with subtle differences: clocking behavior, addressing, transaction format, etc. Basically, they're all compatible, except when they're not of course. Under Linux, a wide variety of I2C  devices are supported; in addition, Bluewater regularly writes drivers as we use new I2C devices in our designs. At the time of writing, custom-supported I2C devices include:

In addition to Linux, we also use I2C devices in lightweight embedded solutions: Of course, this list will keep expanding as additional devices are used in products.

The secret to maximising your productivity is ensuring you have the correct tools for the job. When it comes to bringing up a new kernel for a processor that you have not supported before, an embedded ICE is a must have. Before now Windows CE has lacked a set of high quality tools for kernel bringup. Normally the first step in CE development is the creation of a the Kernel Independent Transport Layer (KITL) so that you can debug your kernel drivers over Ethernet. The problem with this is that you need a large portion of the kernel and Ethernet driver to be working before you can do any debugging. As soon as any problems occur in the kernel, the entire debugging session locks up. We have been lucky as an ARM tools distributer to be able to trial a pre-beta version of the Windows CE 6.0 eXDI2 drivers for the Real View ICE. The driver plugs directly into Visual Studio and provides source level kernel debugging of an embedded platform as if it was a desktop application. It has allowed us to single step through the kernel of our AT91SAM9260 platform before the kernel was up and running. No longer do we need to toggle LED's in a seemingly random sequence of pulses to indicate boot progress! The Windows CE 5.0 eXDI2 plugin for Platform Builder is available for general release by registering on the ARM website. http://www.arm.com/products/DevTools/eXDI2RVI.html The Windows CE 6.0 eXDI2 plugin will be available for general beta testing in the very near future.

Two of us are attending an ARM meeting in Hong Kong this week. There is a quite a large turn-out of companies across Asia including Singapore, Taiwan, China, Korea, and of course New Zealand. What struck me as I looked at the group about to go out for dinner last night, was that there were more people there among ARM's tools distributors in just a single region, than worked for ARM in total when I joined just 14 years ago. ARM shipments passed the 10 billion mark last year and the current run rate is over 3 billion per annum. Of interest particularly is the massive growth in low-end ARM micros. The Cortex-M3 is 'only' shipping about a quarter of a billion units per annum, but volume is more than doubling each year. When the $1 micro was announced I wrote a short paper about the possible impact (available here). It seems that ARM is well on the way to making good on some of the benefits identified, particularly in terms of quality of tools, and the productivity of engineers developing with low-end microcontroller technology.