Zaurus leads embedded Linux-general Linux technology-Linux programming and kernel information. The following is a detailed description. The Sharp Zaurus handheld system is an embedded Linux®Peter Seebach, a pioneer in the system, believes that it is a good idea to contribute to a technology in its early stages. In this Linux charm series, Peter will take a look at the Zaurus SL-5600 to better understand its history.
George sanguana once said, "Those who forget history are destined to repeat history ". But in the computer design industry, this warning does not seem to be taken seriously. Many companies often repeat the same errors and lessons and make repeated improvements to their previous systems.
When Sharp Zaurus declared for the first time that they wanted to "run Linux", the Linux community was so busy that there were both cheers from fans and rumors. A few years later, some handheld devices running Linux have been drawing inspiration and ideas from Sharp's work, even though Linux-based Zaurus has gradually withdrawn from the U.S. market.
This month's Linux charm article will introduce Sharp Zaurus SL-5600. This is the second retail version (the first retail version is the SL-5500, a version after the SL-5000D development version), this article will introduce the source of current efforts in this field.
The design of the embedded Linux system has added many considerations. Zaurus is the first system to solve these considerations. The Linux community was very enthusiastic at the beginning, but the device did not achieve the desired success in the U.S. market.
Hardware Design
When designing an embedded system, a major driver is the hardware function. Zaurus uses a typical hardware platform for handheld computers:
CPU is 400 MHz Intel®XScale; Linux is called an ARM processor, because gcc does not try to closely match the market terminology.
64 MB flash memory and 32 mb ram are installed on the system. 5500 has 32 MB flash memory and 64 mb ram; the result is that some programs can run on 5500, but cannot run on 5600.
On the other hand, 5600 can effectively solve problems caused by power outages.
It has a 320x240 screen, which is a typical setting for Embedded PCs. (In the future, this module will be upgraded to a screen of 640x480, which looks quite comfortable .)
It also has CF (Compact Flash) and SD (Secure Digital) slots that support non-storage devices, such as 802.11b wireless CF cards or Ethernet adapters.
Like most PDAs, Zaurus also has some common keys, but it also has a small hidden keyboard. This keyboard is a real selling point; compared with handwriting recognition, even a very small home disk is also a great improvement. You can use the keyboard, which is indeed surprising.
The 5000 and 5500 hardware designs are very similar. Later, the module was designed with a shell. It provided a larger keyboard, and the screen could be turned up to form a Traditional Portrait PDA screen, it has an input pen, which is the same as most tablet PCs currently use.
5600 provides some improvements compared with 5500, but the changes from StrongARM processor to XScale processor are not very smooth. The new module greatly improves the battery life (the method is very simple and the battery size is doubled ).
The difference between 5500 and 5600 reflects the feedback provided by PDA users for Sharp. In most cases, these changes reflect the general considerations of PDA users. For example, storing user data in flash is a good solution. If the battery power is insufficient, PDA users may face the same risk of data loss, this solution can solve this problem well. In addition, the 5600 keyboard is easier to use than the 5500 keyboard.
Construct PDA
Many assumptions about embedded systems by Linux developers cannot work on PDAs. PDA users want to run new applications, store data, and use these programs and data later. In addition, since 3Com introduced the first Palm Pilot, PDA has been using the GUI. The 9600 baud rate serial port is not a typical choice.
Desktop Linux is not suitable for PDAs. Most PDA users do not like to log on to the system first, and then start the X server explicitly. In addition, the 320x240 screen is not enough for text terminals. Virtual desktops, Multiple mouse buttons, and other typical desktop features are not suitable for a small screen with an input pen.
Zaurus uses the Qtopia desktop environment instead of the X server. You can also start X server on this hardware (after all, the memory and processor processing capabilities of this machine are higher than those of the memory and processor processing capabilities of the Server Load balancer instance on the iSCSI workstation ), however, small footprint prints and small displays are not suitable for the assumption of X workstation.
The application provided by Zaurus for PDA is only a weak unit on the PDA. This is just a very young group of applications, and the features are not as complete as those on the Palm platform.
Adjust Linux
One challenge for Linux to work on PDA is to determine when to use common Linux methods to implement certain functions and when not to use these common methods. The results will not always be the same as what the user wants. For example, determining when or whether a password is required is a challenge. Most users do not want to use password prompts on their PDAs.
Zaurus has completely abandoned security concerns from the very beginning. The GUI runs as the root user, but even if it does not run as the root user, you do not need to enter the root password. The su command can implement this function.
Zaurus is based on BusyBox (0.60.4. This best tool allows many programs to be linked into an executable program; however, this kind of organization is a bit strange. BusyBox is embedded with support for gzip, but it also provides a zcat tool. However, this is a very reasonable decision, because it can save a lot of space.
Start
The rc. d system is completely retained, although the init-level definition may not be exactly the same as that in the Desktop Linux system:
Listing 1. Running levels on SUSE Linux and Zaurus
