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Day of the triffids

Board level solution enables remote security systems.

There are many reasons why engineers turn to board level solutions when creating their designs. One reason near the top of the list is that someone else has done a lot of the work for you. And this is important bearing in mind the time to market pressures which all companies face. But a board level solution can often bring with it economies of scale: it might well be cheaper to buy in a board than to design it yourself.

One company which has made a name in the supply of embedded control systems to oems and industry is Cambridge based Micro Robotics. It claims that its products are ideally suited to short development cycles in low and medium scale manufacture.

Karl Lam, the company's technical director, outlined the company's origins. "We're about 15 years old and our first products were add on for the BBC Micro. One of these became a control computer in its own right, but programmed from the BBC Micro. People were taking the computer and using it in industry, even though it wasn't an industrial product." That add on turned into the Scorpion K4 range of control computers.

One of the major selling points for the Scorpion range is that it uses an object oriented language, called Venom. Lam claimed that Venom was the first object oriented language to be developed for use with 8bit microcontrollers. "Twelve years ago, there was nothing like it," he continued.

Scorpion controllers are now built into a range of applications. For example, all power supplies for Channel 5's transmitters feature Scorpion boards and all satellite downlinks in Thailand have a K4 built in.
Plugging into a host pcb, the K4S can control a range of functions. Using its system bus and general purpose I/O, the board can connect to up to 160 digital I/O channels, as well as an unlimited number of analogue I/O.
Communications are supported by two independent serial ports and an output only serial port. Lam admits the board is not as 'connected' as he would like. "But the modules do have a networking protocol based on RS485, along with i2c and spi." TCP/IP will be introduced in the future, he added.

Because K4 can be real time and multitasking, it makes things easier for engineers. Lam explained: "Say an engineer is starting a new project. It might take a week for the project to get going. With K4, they can be up and running in 20minutes."

The difference which Micro Robotics claims for Scorpion is the control language Venom. According to the company, Venom combines the simplicity of Logo – originally developed for use by schoolchildren – with the sophistication of objects. Lam noted: "The combination of K4 and Venom allows those without software expertise to take their own expertise and to put the K4 card into lower technology electronics, then write software in an easy language; accomplishing what they want to."

Micro Robotics developed Venom because, at the time, it didn't have anywhere else to go – in effect, it would have been offering the same as everyone else. Lam continued: "We had to have an interpreted language because we couldn't put a compiler on it in an 8bit device. Having taken that decision, it isn't C and, in some ways, it's easier to use and more powerful than C."

Venom has a high level block structure and is inherently multitasking. "If you want to control a graphic lcd," Lam said, "you just select a block. Compare this to several months if you want to write an lcd driver for a microcontroller and display."

One company using Scorpion boards to great effect is Tonbridge based Triffid RDS, a developer of mobile security systems. Roger Dennis explained: "We've been working with Micro Robotics since the 1980s." According to Dennis, one of the attractions is the programming language. "It's half high level, half not so high level. But it does allow you to get into it at the machine level."

Dennis has been designing security systems since the early 1970s. "I designed my first wireless security system in 1971," he claimed, "but struggled with the availability of technology." But his break came with an exhibition in Earls Court. "Microsoft was exhibiting and wanted something to protect its stand. The company responsible for security came to me and we produced the first Triffid." Dennis notes the name Triffid was chosen because the device 'looked like a pot plant'.

"The product has evolved," Dennis accepts. "The first ones were rather knocked together. Now, the nature of our business is to develop rapid deployment security systems that can be put anywhere at any time, deal with a situation, then be removed when not required."

Triffid began as a device that could detect human presence, make a noise and flash lights. Now, the device has evolved to take advantage of gsm communications, local paging and rf transmission.

Dennis says the addition of local paging to Triffid was quite an achievement. "The product is quite complicated, but we have managed to get the K4 board to do the maths involved."

There are currently four Triffid models available. Two are aimed at external application, the other two are for internal use. All use an interface board, which the K4 plugs into.

The same radio device – from Wood & Douglas – is used for the paging and radio telemetry options. "It has a synthesisable crystal," Dennis continued, "which means we can change functionality through software. We use the K4 for the transceivers because it processes all the information."

Triffids use a range of sensors to detect movement. The TO2, for example, can support two all weather sensors with a range of 180m. As the sensors monitor a 90o segment, two Triffid TO2s can handle a square of 180m perimeter. Four analogue channels allow environmental conditions to be monitored. It features a uhf transmitter with a range of 10km, which allows data to be relayed to a central control room.

According to Dennis, Triffid capability is 'all down to the K4'. "Sensors are just sensors; in the end, it's how you deal with the information from the sensor. It's crucial all Triffid units have a level of intelligence."
Remote operation means the Triffid has to be battery powered. One of the analogue channels is used to monitor the condition of the rechargeable battery stack and this information is transmitted routinely.

Amongst Triffid users is the Tate Gallery. According to Dennis, the gallery keeps partitioning its displays and the cctv security system can't always 'see' everything. Deployment of Triffids allows security to be maintained. Triffid TO2s have also been tested by the MoD and at Kew Gardens. Dennis explained: "We did a test at Kew Gardens, which wanted to measure temperature and humidity, as well as monitoring intruders. The three available analogue channels allowed us to do this."

The K4S is currently designed around Hitachi's HD6303 microcontroller, but it is in the process of being upgraded. A new board based on the H8S will be unveiled in the New Year.

"We've tried to have as few differences as possible between the two models," said Lam. "Now, we're only changing speed." Lam added that, nowadays, clock speed is not really an issue. "It's how quickly code can be executed and we've achieved an improvement of 20 times."

Author
Graham Pitcher

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