简单介绍我在学校的项目的技术 (based on arm7)

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Recently, Linux are being widely used as
an Operating system for the embedded systems. A wealth of applications and
development tools make Linux an attractive platform. Its development is mostly
due to open source code and efficient design. Linux has become more popular as
an operating system on PDA with the advent of GUI applications.
My project begins at 2001. The CPU is arm7 (sa1100). Here is some technical introduction about the hardware platform, bootloader, OS and cross-compiling environment.

Implement Embedded Linux on PDA

1. Introduction

Familiar Linux is presently available for
the Compaq iPaq. Since the architecture of iPaq is quite different to the
normal desktop computer, we have to develop new application program for this
Linux embedded system.

2. Overview

During the development of
embedded Linux on PDA, the source code is written and modified in the Linux on
desktop. And the source code is compiled by the cross compiler for Arm Linux.
It is a compiler used to compile a source code for arm target platform.
The Familiar Project is
composed of a group of loosely knit developers all contributing to creating the
next generation of PDA OS. Currently, most of our development time is being put
towards producing a stable, and full featured Linux distribution for the Compaq
iPAQ h3600-series of handheld computers, as well as apps to run on top of the
distribution. The hardware and software requirements are listed as following:

2.1. Hardware Requirement:
1.     
Compaq H3600 iPAQ
2.     
Serial cable
3.     
Serial cradle

2.2. OS/Software Requirement:
1.     
Red Hat Linux 7.3
2.     
Cross compiler for ARM used in Redhat Linux
3.     
GCC
4.     
Root Image – Familiar v.0.5.2 task-bootstrp.jffs2)
5.       A
terminal emulator capable of performing xmodem uploads – Hyperterminal
6.     
ActiveSync Software (on host pc)
7.     
Bootloader – ARM Bootldr 2.18.01
8.     
Some applications for PDA – qpe application

As we use Compaq iPAQ h3600 as the
hardwire, and it is in the series of Compaq iPAQ of handheld computers, so
Familiar Linux is surely an ideal OS platform that we place our target on.

Currently Familiar's Linux distribution
supports some of the following key features:
Entirely
     based on XFree86's/keithp's Tiny-X server.OpenSSH's
     ssh. JFFS2 supported,
     which enables the read/write access to the Flash. Binary and
     Library distribution compatible the ARM target.a good
     wealth of peripherals and GUI applications  . Full
     package support based on ipkg.

The current software release versions are:
Familiar Project Linux v0.5.1 for the IPAQ
     H3600.
For free download, please visit:
http://familiar.handhelds.org/
        

3. Implementation Details
3.1. Setup target environment
The primary work is to install Familiar
Linux v.0.5.2 on iPAQ H3600 [1, 2]. The main tasks in this procedure are backup
wince, install boot-loader and install root image. Finally we can boot PDA with
embed Linux successfully. In the part, the only dangerous step is to fresh the
boot loader. So you should be care of this. The detailed steps are as follows:
Backup WinCE
Connect your iPAQ
     via the USB or serial cradle or cable. If using a serial
     cradle or cable, then configure your iPAQ to use the serial port for
     ActiveSync.
·        
Select settings from the Start Menu (the Microsoft flag
icon)
·        
Click the Connections tab, and then double-click the PC
icon.
·        
Ensure the automatically synchronize when serial cable
is connected using is checked.
·        
Change USB to 115200 baud defaultly.
·        
Click OK (top right of the screen).
Use
     the ActiveSync application to
     connect to your iPaq 3600 from your PC. If there is not an ActiveSync icon
     in the tool tray, then use the Start->Program->ActiveSync menu item
     to start it. Copy
     BootBlaster_1.18.exe to the default folder on your iPaq from your Windows
     machine using drag and drop or cut and paste. You may safely ignore any
     messages that say it "may need to convert" file formats. Copy
     bootldr-2.18.01.bin to the default folder on your iPaq from your Windows machine.
     Again, You may safely ignore any
     messages that say it "may need to convert" file formats. On your iPaq H3600,
     find BootBlaster_1.18.exe wherever you put it, and then execute
     BootBlaster_1.18.
7.     
Root Image – Familiar v.0.5.2 task-bootstrp.jffs2)
From the
     "Flash" menu, select "Save". This will save a copy of
     your current bootloader to DRAM on the iPAQ (under the name
     "saved_bootldr.bin"). Copy the
     "saved_bootldr.bin" off of your iPAQ and put it in a safe place
     in case you wish to restore it later.From the "Flash
     menu, select Save Windows gz This will copy and compress all the
     flash on your ipaq into a .gz file. This will take a while. After it is
     complete, copy this file to your PC to save it.
Note: Please be patient! This will take several minutes.
Installing the Bootldr [4]
From the
     "Flash" menu on BootBlaster, select "Program". A file
     dialog will open allowing you to select the bootloader to use. Select the
     bootloader from step #5.Wait patiently. On my iPAQ, it takes about 15 seconds to program the
     bootloader. During this time, the iPAQ just sits there.If it sits for more
     than 15 seconds with no activity, then reboot the iPAQ by pushing the
     recessed reset button at the bottom right and repeat this step.
Check the Install
After “flash”, it
     will auto-verified. If not, do it manually. From the "Flash"
     menu on BootBlaster, select "Verify". If it does not say
     that you have a valid bootloader, do NOT reset your iPAQ, try
     programming the flash again. If that doesn't work, program your flash with
     your saved bootloader. (Be careful! This is the only risk!)
Reboot the iPAQ
When the iPAQ is reset, by default, it
     will boot Windows CE.Reboot your iPaq
     H3600 by pushing the recessed reset button at the lower right of the unit
     while holding the center of the joypad. Set up Hyperterminal
     first
·        
115200 baud
·        
no flow control
then put the iPAQ back in the cradle. At this point,
either type a space in the terminal emulator or push the calendar button on the
iPAQ to get the bootldr's prompt "boot>".
Before proceeding to Linux installation, unlock flash
with this command: pflash 0x40000 0xffff 0 by typing it at the boot prompt.
The bootldr will automatically protect itself upon boot
if the bootldr sector is not locked, however you may do so manually with the
command: pflash 0x0 0x3ffff1.
Performing Boot-loader Configuration [5]
setup flash
     partitions.
·        
At the "boot>" prompt, enter: partition
reset
Here's an example of prompt display:


  boot> partition resetargv[1]=resetdefining partiton: bootldrdefining partiton: rootboot>                                 
  
Flashing the Filesystem
At the
     "boot>" prompt, issue the following command: load root Proceed to send the
     proper fileimage-bootstrape[
here
] via xmodem, using
     Hyperterminal. Then bootloader successfully erased, wrote, and verified
     the filesystem image.
Boot the Installlation for the First Time
At the
     "boot>" prompt, type: boot Familiar Linux
     start, and you need login in as root using rootme as the password.

3.2. Setup
Host Environment

This
section contains information on setting up a GNU toolchain For ARM targets. It
details in both some pre-compiled toolchain which you can install, and how to
compile your own toolchain.

3.2.1.
Install pre-built toolchain
3.2.1.1. Download tool-chain

The
toolchain actually consists of a number of components. The necessary  crosscompiler tools (arm targets) for a
development environment are:
              
·           
arm-linux-gcc-*.rpm
  (The compiler itself gcc)
              
·           
arm-linux-binutils-*.rpm
         (A set of tools for manipulating
binaries)
              
·           
arm-linux-glibc-*.rpm
(C-library glibc)
              
·           
arm-linux-kernel-*.rpm           (Kernel source code of ARM Linux)
The most convenient approach to
install cross-compiler tool-chain is to use rpm. The download URL is
ftp://ftp.netwinder.org/users/c/chagas/arm-linux-cross/RPMS/
. The packages are suitable for Linux version 2.4.

If this link is not available,
please try this:
http://www.arm.linux.org.uk
(CVS supported)

3.2.1.2. Install the tool-chain

If there is rpm package, please use
the four commands to install:
rpm -ivh arm*-binutils*.rpm
rpm –ivh arm*-gcc*.rpm
rpm -ivharm*-glibc*.rpm
rpm –ivh arm*-kernel*.rpm
Install it once with:
rpm -ivh arm*-binutils*.rpm
arm*-gcc*.rpm arm*-glibc*.rpm arm*-kernel*.rpm
But sometime version conflicts
happened. Thus to install it one by one could be safer. The installation path
of arm-linux toolchain is /usr/local/arm-linux.

3.2.1.3. Setup environment variables

In
order to make the toolchain work, please set a couple of variables:
PATH=/usr/local/arm-linux/bin:$PATH
LD_LIBRARY_PATH=/usr/local/arm-linux/lib:$LD_LIBRARY_PATH
CC=arm-linux-gcc
CXX=arm-linux-g++
PREPROCESSCMD="$CC -E"
LD=arm-linux-ld
PS1="[arm-linux] $PS1"

3.2.2.
Cross compile C-program

This
sub-section shows how to build C program for ipaq using the cross compiler.
1.
For a sample hello.c , we'll make a new directory “hello” and do the following.
mkdir
~/hello
cp hello.c ~/hello
cd ~/hello-world
To build, call the compiler,
with the right options, with the command
arm-linux-gcc -Wall -g -o hello hello.c
2.
For a complete set of source code, In the Makefile, add some lines:
CC=arm-linux-gcc; LD=arm-linux-ld
An alternative approach is to
issue a command like:
Make
CC=arm-linux-gcc LD=arm-linux-ld all


3.2.3. Compile your toolchain

This subsection introduces how to compile your toolchain.
This is useful when the pre-built package isn’t available.
Build binutils ...
Download the
binutils-2.10.tar.gz

# tar zxvf binutils-2.10.tar.gz# cd binutils-2.10# mkdir build# cd build# ../configure --target=arm-elf --prefix=/usr/local/gnu# make# make install [Note: write access to /usr/local/gnu is required]
Build gcc ...
Download the
gcc-2.95.3.tar.gz

# tar zxvf gcc-2.95.3.tar.gz
Apply patch from Philip Blundell to change
the Position Independent Code generation for ARM:
# gzip -cd
gcc-2.95.3-arm-pic.patch.gz
| patch -p0# cd gcc-2.95.3# mkdir build# cd build# ../configure --target=arm-elf --prefix=/usr/local/gnu --disable-threads# make LANGUAGES="c" [Note: be sure /usr/local/gnu/bin is in the PATH list]              
Continue installing the C compiler:
# cd gcc# make install
Build libc ...
Download the
newlib.tar.gz

# tar zxvf newlib.tar.gz# cd newlib-1.8.1# mkdir build# cd build# ../configure --target=arm-elf --prefix=/usr/local/gnu                --enable-target-optspace# make# make install
Build other
languages supports in gcc ...
# cd gcc-2.95.3/build# ../configure --target=arm-elf --prefix=/usr/local/gnu# make LANGUAGES="c c++"# make install
3.3. Compiling the ARM kernel on
your desktop

If
a development on the extension & modification of ARM-Linux kernel will be
taken care of later, the experiment of compiling ARM-Linux kernel should be
done now. This section describes how to do that.

3.3.1.
Requirements

Grab
the kernel-sources from handhelds.org. You find them e.g. under
ftp://lorien.handhelds.org/pub/linux/feeds/demo/
.
Copy
the tarball into /usr/kernel and extract it using tar xvfz somekernel.tar.gz.
Set
a link /usr/local/linux-arm-kernel to the kernel using "ln -s
/usr/kernel/somekernel.x.y.z/kernel /usr/local/linux-arm-kernel".


3.3.2.
Using the CVS repository of handhelds.org

To
get the newest (or an older) version of the kernel sources, you may use the
anonymous CVS access. This sub-section describes how to get the sources for
kernel 2.4.16-rmk1-hh15 (familiar 0.5.2).
Create a directory,
     where the kernel sources should be stored. You will need approx 150 MByte
     of disk space. Enter this dir and
     export the CVSROOT variable typing
     export
     CVSROOT=:pserver:anoncvs@cvs.handhelds.org:/cvs login the server
     typing
     cvs
     login. Enter the required
     password anoncvs. You should be looged in. If you have already
     the kernel repository available (did already a download) before, use the
     next step to go on.
     cvs
     co linux/kernel will prepare
     your linux/kernel repository. Now you can checkout
     your kernelversion.
     cvs
     co -r K2-4-16-rmk1-hh15 linux/kernel grab the sources from the kernel repository.

3.3.3.
Compilation and installation of the kernel

Become
superuser, enter the subdir linux/kernel and type
#cp arch/arm/def-configs/h3600 .config#make oldconfig
to
get the config done for the h3600 ipaq.
Type
qtarm to get all necessary environment variables set. Qtarm script file must
includes such information:
       #!/bin/bash        # qtarm        # script file to set up Cross-compiler (arm-linux-cc)        # -------------        # Compiler-Path is where your Cross-compiler is located        COMPILER_PATH=/usr/local/arm-linux        # Kernel-Path where your ARM-Kernel is located        KERNEL_PATH=/usr/local/linux-arm-kernel        # LD_LIBRARY_PATH has to be added by COMPILER_PATH lib dirs.        LD_LIBRARY_PATH=$QTDIR/lib:$COMPILER_PATH/lib:$LD_LIBRARY_PATH        # Installation PATHs .....        # Install-PATHs are used to define the installation PATH        # for self created libs (used for qt/emb/arm)        LIB_INST_PATH=/usr/local/lib        INC_INST_PATH=/usr/local/include        export LIB_INST_PATH INC_INST_PATH         # -------------------------------------------------        # Programs .....        # some Makefiles use the follwing Environment variables        # to find the right compiler / linker        CC=arm-linux-gcc        CXX=arm-linux-g++        CCX=arm-linux-gcc        CXXX=arm-linux-g++        COMPILER=arm-linux-gcc        LINKER=arm-linux-g++        # the strip-program (strips down the size of the binary        # deleting all debug-information)        STRIP_PROG=$COMPILER_PATH/bin/arm-linux-strip        # some Makefiles use the follwing Environment variable        # to define a preprocessor        PREPROCESSCMD="$COMPILER -E"        export STRIP_PROG COMPILER LINKER PREPROCESSCMD CC CXX CCX CXXX
Type #make dep
clean bzImage modules and drink some coffee (it may take half an hour).
Enter make modules_install (they are standardwise are
installed into /lib/modules/kernelversion). If you dont want that, you can set
$INSTALL_MOD_PATH as a prefix.
After
the kernel is ready, and the link is remade, the kernel can be found in
/usr/local/linux-arm-kernel/arch/arm/boot. The file bzImage is a new kernel
binary.

3.4. Build Your Image
3.4.1.
Creating jffs2 Image

Refer to
The Familiar Project
for
procedures on installing linux onto your IPAQ. The best approach to create a
jffs2 image is to download an old version filesystem and modify it to what you
want. Below is a jffs2 image of the filesystem, as well as a tarball of the fs
tree. (* refers to the version).
kernel
image   
(zImage-*)
root
image    (task-boostrap-*.jffs2)
root
tarball    (task-boostrap-*.tar.gz)

After you prepare a full set of filesystem,
make the image by:
#mkfs.jffs2 -r root -o root.jffs2 -e
erasesize -p
root:           the directory containing the files to
go in the image.
root.jffs2:    the name of the filesystem image.
erasesize:    the sectorsize of flash on the target
machine.
erasesize is
0x40000 for H3600

Erase the whole block to contain the
filesystem, then load the constructed .jffs2 image in the beginning of the
block device. As of bootldr 2.14.5, it automatically erases the whole partition
if 16 (bit 4) is one of the flags set in the partition definition.
You can obtain mkfs.jffs2 from
ftp://ftp.uk.linux.org/pub/people/dwmw2/iPAQ/mkfs.jffs2

3.4.2.
Build ipkg of C-program for Compaq IPAQ

IPAQ
is a good tool to build the C-program for IPAQ. The steps of compile are shown
next.
1) Copy the ‘ipaq-build’ into /usr/loacal/sbin
2) Create the directory “hello”, which should have two
sub-directories-“CONTROL” & “destination directory” . a subdirectory
“destination directory” is the destination directory on IPAQ.
/hello/CONTROL
/hello/usr/bin (*only for reference, modify it to your
own directory)
3) In “CONTROL”, a file named "control" is
created. The sample file (attached in the zip file) is:
###Begin:
CONTROL/control for ipaqrs
Package:
ipaqrs
Priority:
optional
Version: 1.0
Date: July,
12th, 2002
Architecture:
arm
Maintainer:
Familiar User
Depends:
Description:
serial-comm program
###End:
CONTROL/control for ipaqrs
4) Copy the binary files into “/hello/usr/bin”.
5) Issue the command : ipkg-build directory
[destination directory]

3.5.  Install Application
3.5.1.
Usage of ipkg

Given the assumption that IPAQ is
installed with Linux. The application can be transferred from desktop PC to
IPAQ via xmodem, using Hyperterminal on windows (minicom on Linux). More
details is in appendix A.
1)     
Send hello_*.ipk to /tmp
(on ipaq)via zmodom, using hyperterminal.
2)     
Install the ipk by
entering “ipkg install /tmp/hello_*.ipk”.
3)     
The file is installed
under the directory /usr/bin
Usage
of ipkg:
install : Install package  remove :  Remove package  list      List available packages and descriptions files   List all files belonging to  search   Search for a packaging providing  info [] [] Display all/some info fields for  or all status [pkg] [] Display all/some status fields for  or all depends   Print uninstalled package dependencies for  
3.5.2.
Installing ipkg on IPAQ

Install
application [
here
]
via xmodem
Send Qtopia_*.ipk to
     /tmp (on ipaq)via zmodom, using hyperterminal. Install the ipk by entering “ipkg
     install /tmp/Qtopia_*.ipk”.
Continue
installing the following ipkg:
h3600-utils, apmqt-embedded,
     qpe-taskbar, qpe-base, qpe-sounds, qpe-pics
At the
"boot>" prompt, type: reboot
After the system
reboot with the newly install package, a qpe GUI interface is built. Install
other Qtopia packages:
Qpe-filebrowser,
qpe-handwriting, qpe-keyboard, qpe-qipkg, ape-embeddedkonsole, qpe-systemtime,
qpe-textedit, ipaqrs_2.0_arm.ipk……

3.5.3.
Install applications without iPKG

1. Connect IPAQ to desktop with serial cable
2. Send executable file to
IPAQ (/tmp) via zmodom, using hyperterminal/minicom.
·        
Open hyperterminal,
choose zmodom transfer, choose target file from the browser.
·        
Waiting, this is very
fast.
3. Copy .o file to /usr/bin.

4. Online
Resources:
1.      Compaq iPaq Project: http://www.handhelds.org/

2.      ARM Linux Project:
http://www.arm.uk.linux.org/~rmk/

3.      Download toolchain:
http://handhelds.org/download/toolchain/


References

[1].
Tools-Chain How-to,
http://www.aleph1.co.uk/armlinux/docs/toolchain/toolchHOWTO.pdf
[2].
How to build ipkg package,
http://www.handhelds.org/z/wiki/BuildingIpkgs
  
[3] How to
create a custom jffs2 image for the iPAQ,
http://internet2.motlabs.com/ipaq/howto/custom_jffs2_ipaq.htm

[4] How to install bootldr,
http://www.handhelds.org/feeds/bootldr/install.html

[5] How to install familiar Linux,
http://familiar.handhelds.org/familiar/releases/latest/install/H3600/install.html
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               

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