The Symbian OS (779886), страница 79
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Motorola SlimLite and b. Nokia 3110 phonesusers learn to ‘punch in the number before trying to contact the network’[Lindholm et al. 2003, p. 75].Typical screens that year were 84×48 pixels, monochrome, giving 3 +2 character lines (3 lines of ‘user’ text and 2 status lines). A typical 1997Nokia (based on their DCT3 hardware platform) had 400 physical parts([Lindholm et al. 2003]). DCT4 arrived in 2001 and halved the numberof parts to 200.Mobile network data services were largely unused except for SMS,which the analysts were still describing as underused.
But the two-boxPDA–phone solution, using a GSM phone as an infrared or serial cablemodem, was seen as the coming thing for enabling email and Internetaccess and fax transmission from PDAs via phones.The still somewhat revolutionary alternative could be glimpsed,though, in the Nokia 9000 (Figure 15.4), Nokia’s first generation Communicator and the first converged PDA–phone device, introduced in1996.Figure 15.4Nokia 9000THE PHONE OPERATING SYSTEM377ConvergenceConvergence may or may not have been inevitable but, despite its clunkyphysical form factor and monochrome display (640×200 pixels), theNokia 9000 had put it on the cards.
(It was a big, exciting, and very secretproject inside Nokia; so much so, according to [Lindholm et al. 2003,p. 74], that no-one wanted to work on basic phones, which suddenlylooked ‘trivial’ in comparison. Lindholm’s Navi-key project had a hardtime competing with it for resources.)7The two-box solution, pairing a data-centric handheld such as thePsion Series 5 with a communications-centric GSM mobile, still seemedto be where the market was leading.
Convergence, on the other hand,seemed to suggest putting a phone into a Series 5 or, more to the point,putting the Series 5 operating system into a phone. At some point, itbecame the inevitable next step.Putting a Phone into the Series 5The challenge which Symbian’s engineers faced was to take an operatingsystem that was designed and created with an almost obsessive attentionto the details of a particular product context and evolve it to suit a differentproduct just as well.
It does not seem far to travel, after all, from the (ARMbased, pocket-sized, 1/2 VGA screen, clamshell-case, keyboard-centric,battery-powered) Psion Series 5 PDA to the (ARM-based, pocket-sized,sub-1/2 VGA screen, clamshell-case, keyboard-centric, battery-powered)Nokia 9210 Communicator. And it seems not that much further from theCommunicator to an even more phone-like and less PDA-like device, infact to a mainstream (if high-end) phone.The Symbian OS mantra ‘built for mobile phones from the groundup’ doesn’t quite tell the complete technical story.
The operating systemwhich shipped in the summer of 1997 in the Psion Series 5 knew exactlywhat device it was built for: a clamshell, AA-battery-powered, always-onPDA, with a keyboard, a touch screen and a couple of serial ports. It wasoptimized for mobile devices, but it also required several evolutionarysteps to properly address mobile phones specifically.Peter Jackson:I don’t know the point at which we really got to grips with the idea that wewere making an operating system for a phone. Because when we started weweren’t, we didn’t. We were making an operating system for a Series 5, noteven for a generic PDA but for a Series 5, and for other things like it that wemight invent.7Lindholm was later the architect of the Series 60 user interface and arguably the driverbehind its platformization.37815.4JUST ADD PHONETelephonyTelephony services in Symbian OS are organized around the ETel serverand framework, which is at the heart of the application-side interactionwith the phone baseband or, as it was originally conceived, any modemat all.As Andy Cloke remembers it, development work on ETel started evenbefore the Series 5 had shipped.
See Figure 15.5.Andy Cloke:We started doing ETel when Roger Nolan8 was running the Comms group.I don’t think it was entirely clear that we were going to do the next NokiaCommunicator. At least, it wasn’t clear to me at that point. There was stillquite a focus on PDAs. Certainly, the thought that we wouldn’t be doing PDAshadn’t become clear. So it could have been PDAs in a variety of forms: themodem could have been built in; it could have been a plug on; it could havebeen wirelessly linked.
It was quite different from the way we are today.The device that came to market was the Nokia 9210 Communicator,the direct descendant of the Nokia 9000. But at least two other phonebased projects ran more or less concurrently with the CommunicatorApplicationsETel APIExtensionsETel APIExtensionsApplication levelETel APIExtensionsCore ETel APISymbian OSETel Server and FrameworkTSYHardware adaptationTelephony HardwareFigure 15.58Telephony architectureRoger Nolan had previously been a member of Colly Myers’s kernel team.TELEPHONY379project, one for a Philips phone ‘companion’, which did not come tomarket, and one for the Ericsson R380.
(See Chapter 2 for more about thebackground to these early projects.)The starting point for the design was not really a converged deviceat all. While assumptions had moved beyond being simply an operatingsystem for the Psion Series 5, the thinking was closer to a ‘super PDA’.Andy Cloke:We were thinking about the possibility that you might have multiple modemsthat may appear and disappear. So the concept of PCMCIA cards that couldbe inserted and removed dynamically was still very prevalent. So that was themotivation for having multiple phones: you might have an internal modemand a PCMCIA modem and another one accessible over Bluetooth, forexample.ETel first appeared in the codeline at version 001 in July 1997 andby the end of the year was providing basic ‘Hayes’ control of a GSMphone (as modem) over a serial connection.
As it happens, the test phonewas none other than a Nokia 9000. If there had been uncertainty aboutwhether the Nokia Communicator project was the target, it was resolvedby the end of the year and ETel was explicitly delivering into the NokiaCommunicator project.Andy Cloke:We established the ETel API first and then, in parallel as I remember, we starteddeveloping an AT-command-based TSY, and we didn’t quite realize how biga job that was. And in parallel with doing that, we started talking to Nokia,to the Communicator development team. I remember going to talk to themand we thought we were going to get completely toasted when we presentedour ideas because we were fairly new to it, and clearly these people kneweverything about telephony and we didn’t.
I can remember coming back onthe plane after the meeting in Tampere and thinking ‘Wow!’ Because we hadexpected to get roasted alive and that hadn’t happened, so we just thought,‘How great we are, we’ve managed to get it right first time!’ It wasn’t until laterthat we realized how easy they’d been on us and how much we had to learn.In the end, we got strong design steers from Nokia and Ericsson.In 1998, the first GSM extensions began to appear; the fax server wasintegrated from a standalone component into the ETel framework (asa framework extension).
By the end of 1998, the code had reached adegree of stability as an alpha-release component of what was by then the‘EPOC Release 5 platform, aimed at the new Psion Series 5MX, a souped380JUST ADD PHONEup palmtop intended to have full phone and networking capability (intwo-box mode).In January 1999, ETel branched for the Ericsson R380 and by May ithad become a component of the ER5u baseline, the so-called ‘wide’ orUnicode build of the operating system, and part of the main codeline.
Bythen, there were multiple licensees taking the component.Andy Cloke:As you can imagine with companies working together but competing in thesame market, there were quite a few political considerations; the opportunitiesfor getting the different parties into a room together were fairly small, and theamount that they would discuss in the room together was also fairly small. Youhave to understand that we hadn’t shipped a phone at this point, the EricssonR380 hadn’t shipped and the Nokia Communicator (9210) hadn’t shippedeither.
So it was difficult for us. In terms of the TSY development, both Ericssonand Nokia were saying, ‘Don’t worry about that, we’ll do the TSY’. We allthought that this was a good thing, little knowing that with us creating the APIand them creating the TSY that plugs into the bottom of it, we were creating anintegration nightmare. If we’d done the TSY design more in parallel it wouldhave been better.
We would have avoided some pain later.ETel Design Goals and ArchitectureETel’s design drivers are clear enough. It was designed to support multipleclients and multiple dynamically loaded TSY modules with the goal ofenabling a PDA to access either a built-in or external modem – indeed,multiple modems at any time – typically to enable data calls (for example,SMS messaging and fax) and Internet access (for example, email andWeb browsing).
From the beginning, there were also some clever phonespecific extras, designed for the case in which the ‘modem’ being accessedwas in fact a GSM mobile phone. For example, SIM toolkit functionsallowed synchronization of on-phone SIM-stored and memory-storedphonebook entries with the PDA contacts application.The design took the existing serial communications architecture as itsstarting point (Figure 15.6). The design goal was to provide an abstractmodel for controlling phones from Symbian OS. Phone hardware wasunderstood in classical Symbian terms as a resource to be shared bymultiple applications with serialized access; in other words, the servermodel applied.
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