Configuration — Platform-specific Configuration Options
The PC platform HAL package is loaded automatically when eCos is
configured for a
pc target. It should never be
necessary to load this package explicitly. Unloading the package
should only happen as a side effect of switching target hardware.
The PC platform HAL package accommodates four separate startup types:
- This is the startup type which is normally used during application development. The board has RedBoot running in low memory and boots into that initially. i386-elf-gdb is then used to load a RAM startup application into memory above 0x00200000 and debug it. It is assumed that the hardware has already been initialized by RedBoot. By default the application will use the eCos virtual vectors mechanism to obtain certain services from RedBoot, including diagnostic output.
- This startup type can be used for finished applications which will be loaded from a floppy disk by the BIOS. The application will be self-contained with no dependencies on services provided by other software. eCos startup code will perform all necessary hardware initialization. Such applications are limited to running only within the bottom 640k of RAM.
This startup type can be used for finished applications which can be loaded using the GRUB boot loader. The application will be self-contained with no dependencies on services provided by other software. eCos startup code will perform all necessary hardware initialization. These applications are loaded above the 0x00100000 boundary and therefore have all of the upper RAM area available.
The load address for GRUB applications is 0x00108000 while that for RAM applications is 0x00200000. This allows a GRUB-loaded RedBoot to occupy the first 1MB of upper memory and while allowing RAM applications to be loaded beyond the second 1MB boundary, avoiding any potential clashes.
- This startup type can be used for eCos applications booting directly from ROM. The ROM startup code for the i386 PC target is experimental at present and ROM startup is therefore unsupported in this release.
Floppy Startup Installation
If an application is built with a startup type of FLOPPY, then it is configured to be a self-booting image that must be written onto a formatted floppy disk. This will erase any existing file system or data that is already on the disk, so proceed with caution.
To write an application to floppy disk, it must first be converted to a pure binary format. This is done with the following command:
i386-elf-objcopy -O binary app.elf app.bin
app.elf is the final linked application
executable, in ELF format (it may not have a
extension). The file
app.bin is the resulting
pure binary file. This must be written to the floppy disk with the
dd conv=sync if=app.bin of=/dev/fd0
Insert this floppy in the A: drive of the PC to be used as a target and ensure that the BIOS is configured to boot from A: by default. On reset, the PC will boot from the floppy and the eCos application will load itself and execute immediately.
Unreliable floppy media may cause the write to silently fail. This can be determined if the application image does not correctly boot. In such cases, the floppy should be (unconditionally) reformatted using the fdformat command on Linux, or format a: /u on DOS/Windows. If this fails, try a different disk.
GRUB Bootloader Support (version 0.97)
If an application is built with the GRUB startup type, it is configured to be loaded by the GRUB bootloader.
GRUB is an open source boot loader that supports many different operating systems. It is available from http://www.gnu.org/software/grub. The latest version of GRUB should be downloaded from there and installed. GRUB is now the default bootloader for Linux and therefore is already installed in many installations.
To install GRUB on a floppy disk from Linux you need to execute the following commands:
grub-install --root-directory=/mnt/floppy '(fd0)'Probing devices to guess BIOS drives. This may take a long time. Installation finished. No error reported. This is the contents of the device map /mnt/floppy/boot/grub/device.map. Check if this is correct or not. If any of the lines is incorrect, fix it and re-run the script `grub-install'. (fd0) /dev/fd0 $
menu.lst is an example GRUB menu
configuration file. It contains menu items to load some of the
standard eCos tests from floppy or from partition zero of the first
hard disk. You should, of course, customize this file to load your own
application. Alternatively you can use the command-line interface of
GRUB to input commands yourself.
Applications can be installed, or updated simply by copying them to
the floppy disk at the location expected by the
menu.lst file. For booting from floppy disks it
is recommended that the executable be stripped of all debug and symbol
table information before copying. This reduces the size of the file
and can make booting faster.
To install GRUB on a hard disk, refer to the GRUB documentation. Be
warned, however, that if you get this wrong it may compromise any
existing bootloader that exists on the hard disk and may make any
other operating systems unbootable. Practice on floppy disks or
sacrificial hard disks first. On machines already running a
GRUB-booted Linux you can just add your own menu items to the
/boot/grub/menu.lst file that already exists.
Certain distributions of Linux, including Red Hat Linux,
supply a version of GRUB which references a configuration file named
GRUB 2 Bootloader Support (version 1.98)
If an application is built with the GRUB startup type, it is configured to be loaded by the GRUB bootloader.
GRUB 2 is an open source boot loader that supports many different operating systems. GRUB 2 is the sucessor to the legacy GRUB boot loader. It has been rewritten and requires a new configuration file that is different from the legacy GRUB loader. It is available from http://www.gnu.org/software/grub. The latest version of GRUB should be downloaded from there and installed. Cygwin users will need to install the GRand Unified Bootloader package on their system.
To install GRUB 2 on a disk drive from Cygwin you will first need to format your disk. Begin by launching a windows Command Prompt with ADMINISTRATOR priviledges. This example assumes that your destination drive is E and the filesystem type is FAT32.
format e: /fs:fat32 /qThe type of the file system is FAT32. WARNING, ALL DATA ON NON-REMOVABLE DISK DRIVE E: WILL BE LOST! Proceed with Format (Y/N)? y QuickFormatting 512M Initializing the File Allocation Table (FAT)... Volume label (11 characters, ENTER for none)? Format complete.
When your drive is finished formatting, Cygwin will automatically mount the drive under /cygdrive/e. Next, launch a bash shell. Cygwin users should run their shell as ADMINISTRATOR otherwise the grub-install program will fail. To install GRUB we need to know the device name for your disk. A second disk drive is usually called /dev/sdb. The C: drive is usually called /dev/sda. Determine your device name by reading the /proc/partitions file. This example uses /dev/sdb as input to the GRUB install program.
cat /proc/partitionsmajor minor #blocks name 8 0 156290904 sda 8 1 102400 sda1 8 2 156185600 sda2 8 16 156290904 sdb 8 17 524288 sdb1 $
grub-install --root-directory=/cygdrive/e /dev/sdbInstallation finished. No error reported. $
cp $ECOS_REPOSITORY/packages/hal/i386/pc/current/misc/grub.cfg /cygdrive/e/boot/grub$
cp redboot.elf /cygdrive/e/boot
After installing GRUB 2, we need to a copy a configuration
file for grub to use. The file
grub.cfg is an example
configuration file that loads redboot.elf. You should, of course, customize
this file to load your own application. Alternatively you can use the command-line
interface of GRUB to input commands yourself. Applications can be installed or
updated simply by copying them to the location expected by the
grub.cfg file. In this example the /boot directory is used.
When installing GRUB on a hard disk, refer to the GRUB documentation. Be warned, however, that if you get this wrong it may compromise any existing bootloader that exists on the hard disk and may make any other operating systems unbootable. Practice on a spare disk or sacrificial hard disks first.
Debugging FLOPPY and GRUB Applications
When RedBoot loads an application it also provides debugging services in the form of GDB remote protocol stubs. When an application is loaded stand-alone from a floppy disk, or by GRUB, these services are not present. To allow these application to be debugged, it is possible to include GDB stubs into the application.
To do this, set the "Support for GDB stubs"
option. Following this any application built will allow GDB to connect
to the debug serial port (by default serial device 0, also known as
COM1) whenever the application takes an exception, or if a Control-C
is typed to the debug port. Ethernet debugging is not supported.
The option "Enable initial breakpoint"
CYGDBG_HAL_DEBUG_GDB_INITIAL_BREAK) causes the HAL
to take a breakpoint immediately before calling cyg_start(). This
gives the developer a chance to set any breakpoints or inspect the
system state before it proceeds. The configuration sets this option by
default if GDB stubs are included, and this is not a RedBoot build. To
make the application execute immediately either disable this option,
RedBoot and Virtual Vectors
If the application is intended to act as a monitor, providing
services for other applications, then the configuration option
CYGSEM_HAL_ROM_MONITOR should be set. Typically
this option is set only when building RedBoot.
If the application is supposed to make use of services provided by a
monitor, via the eCos virtual vector mechanism, then the
should be set. By default this option is enabled when building for a
RAM startup, disabled otherwise. It can be manually disabled for a RAM
startup, making the application self-contained, as a testing step
before switching to FLOPPY or GRUB startup.
If the application does not rely on a monitor for diagnostic services then the serial port will be claimed for HAL diagnostics.
eCos is designed to support typical embedded development and production boards. These usually have a fixed set of hardware devices which are either on-chip or are soldered to the board. The PC target is unusual in that is does not have a fixed ethernet device, instead a variety PCI ethernet cards may be installed in the PCI card slots.
eCos supports different ethernet cards by defining a separate target configuration for each supported device. An instance of eCos or RedBoot configured to use one device will not work with a different ethernet device installed. The following table lists the targets and driver packages for the supported devices.
|Intel Pro 10/100|
|National Semiconductor DP83816||pc_dp83816|
|Intel Pro 1000|
|AMD Lance PCNet32||pc_vmWare|
Entries in the cards column are examples only. There are for example many cards that contain the RealTek RTL8139 or a compatible device. Also be aware that manufacturers may change the device on a particular card to a totally different one without changing the model number.
By default, the system clock interrupts once every 10ms, corresponding
to a 100Hz clock. This can be changed by the configuration option
CYGNUM_HAL_RTC_DENOMINATOR which corresponds to the
clock frequency. Other clock-related settings are recalculated
automatically if the denominator is changed.
The platform HAL defines the default compiler and linker flags for all packages, although it is possible to override these on a per-package basis. Most of the flags used are the same as for other architectures supported by eCos. There are no i386 specific flags that need to be specified for a PC platform.
|2021-02-12||eCosPro Non-Commercial Public License|