Korean firms PalmPalm Technology and M-dream recently announced that they will be incorporating a Linux video game, Puzzle Bubble, into a new Linux-based CDMA/IMT2000 cellular phone that is scheduled to begin shipments this November in Korea. The phone, which uses PalmPalm's Tynux embedded Linux as its internal operating system, is a joint development of PalmPalm Technology and the SK Telecom Central R&D… Laboratory.

To gather more background on this exciting project, which appeared to represent either the first — or one of the first — cellular phones to be based on embedded Linux, LinuxDevices.com's Rick Lehrbaum interviewed Minsuk Lee, VP of Engineering of PalmPalm Technology. Lehrbaum was surprised to discover that this exciting new Embedded Linux based device is not just a cellular phone, but a combination cell phone plus PDA — complete with a 4″ TFT display and a tiny built-in video camera . . .

RL: Do you think this cellular phone is the first to use embedded Linux?

Lee: Sure, it is.

RL: Could you describe the overall features of the phone?

Lee: It's IMT-2000, a prototype mobile phone, which we call “Smart Phone”. It combines the functions of a cell phone plus a PDA. There are two CPUs inside — one for cell phone functions, and the other for PDA functions. The PDA part interacts with the cell phone, for voice communication and Internet connection. The PDA portion of the phone includes a 4″ LCD display and a touch panel, plus a camera and voice codec for H.323. It can handle netmeeting compatible video conferences.

RL: What does the device look like? Is it a cell phone, or a PDA?

Lee: It looks like a PDA but, it has a CDMA cell-phone module within its case. In front side, one can see a 4″ LCD and small camera lens.

RL: So the device resembles a PDA, more than a cellphone. In that case, how do you use a PDA-like cellphone for phone conversation? Do you hold it up to your head and talk/listen? Or, do you have to use an earphone/mic with a thin cable that plugs into an audio jack on the device?

Lee: It still has a speaker and microphone built into the unit for conversation. But, you may feel more comfortable using a headset.

RL: What does the device consist of? Could you take us on a tour?

Lee: These are the basic features . . .

Display and interfaces:

• 4″ TFT LCD display
  
• Touch panel
  
• Bluetooth interface
  
• Camera
  
• Voice codec for H.323
  
• Serial and USB ports are available

  Software related to PDA features:
  

• PalmPalm's Tynux embedded Linux, currently based on Linux Kernel 2.4.0
  
• Qt/Embedded for GUI support
  
• Opera web browser
  
• Its software supports H.323 protocol, VoIP, MP3, browser, etc.
  
• “Sorry, can't talk about the applications right now.”

  Embedded computer (for PDA functions):
  

• Intel StrongARM SA1110 206MHz system-on-chip processor
  
• LCD controller included within SA1110
  
• Boots from on-board Flash memory

RL: How much and what kind of RAM and Flash are provided?

Lee: It has 32MB SDRAM plus 32MB Flash memory. The Flash is based on NOR-type Flash chips.

RL: What was PalmPalm's role in the development of the device?

Lee: First, I'd like to point out that Palmpalm Technology is an Embedded Linux solution company, which has been working with several cellular phone manufacturers to help them develop Linux-embedded mobile phones. We have been preparing Embedded Linux for mobile environments for some time. PalmPalm has developed or integrated all of the software for the device, including both the Linux kernel and the applications. The Linux software has been equipped embedded features for things like power management function, memory management, execute-in-place (XIP) — lots of embedded functions!

RL: What sorts of challenges did you have to overcome? Were there any especially hard problems, and if so, could you tell us how you solved them?

Lee: The main typical problems in these applications are the lack of a power source, and severe memory constraints. We believe we have come up with some good solutions to those problems.

When we began our development, we considered X windows and Microwindows as a GUI platform, but X was to big, and Microwindows was not yet mature. So we had no choice other than to use commercial a GUI [Qt/Embedded].

One big problem, that we still don't have an optimal solution for, has to do with the way Intel's StrongARM processor handles video RAM. StrongARM has an on-chip LCD controller which uses part of system DRAM as its framebuffer space. Unfortunately, when displaying framebuffer on an LCD (this is called “refresh”), the StrongARM consumes too much memory bandwidth. This seriously degrades performance when using high resolution LCDs. To attempt to overcome this, we did some optimization in every part of Linux and the application programs, but, in my opinion, the LCD refresh problem remains serious. This could be avoided, of course, by using another graphic controller IC along with separate framebuffer memory — but that would increase costs and chip count.

RL: Have you produced modifications to the GPL sources? If so, how and when will you make them publicly available?

Lee: We will make all GPL-based sources that we modified openly available.

RL: Could you provide your perspective on using Linux in these kinds of embedded applications?

Lee: Initially, there were some disadvantages in using Linux in embedded applications:

• It's BIG! It needs much more memory than typical embedded RTOSes, but still less than WinCE
  
• Lack of small applications. To overcome this issue, PalmPalm has been forming partnerships with many application software companies. We are now ready to ship “competitive Internet appliances” with PalmPalm's embedded Linux.
  
• No Microsoft compatibility. That is, we still don't have MS-word, Excel, Powerpoint, Media Player, etc. I personally expect that we'll have such solutions by early next year.
  
• Lack of good real-time support. Although there are some efforts to make Linux act like a real-time OS, it still seems to need some intense engineering effort which can increase the total cost.

However, now that we have overcome these factors, for the Internet appliance market, Linux is the best solution, because:

• It's royalty free! (though one usually needs to some pay for some support)
  
• One can easily customize Linux for his/her devices
  
• So many open solutions are already available
  
• It's easier to hire highly skill engineers [for embedded Linux] than for other RTOSes

RL: Thank you!

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This article was originally published on LinuxDevices.com and has been donated to the open source community by QuinStreet Inc. Please visit LinuxToday.com for up-to-date news and articles about Linux and open source.