VxWorks Multi-Image Boot: Universal Startup Method

VxWorks Multi-Image Boot: Universal Startup Method

In embedded production environments, the ability to switch between multiple VxWorks kernel images and applications on a single storage device—without recompilation—is highly valuable.

This guide presents a universal load-type startup method that enables automatic selection and execution of different VxWorks configurations from one hard disk, while keeping boot components fully decoupled.

🔍 VxWorks Startup Fundamentals

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VxWorks supports two primary startup models:

Load-Type Startup

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• Uses bootrom + external kernel image
• Common in development environments
• Kernel is loaded from a file system (e.g., disk or network)

Pros:

• Flexible image updates
• Easy to modify applications

Limitations:

• Requires manual file management when handling multiple images

Bootable-Type Startup

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• Kernel and application are combined into a single image
• Typically flashed into non-volatile storage

Pros:

• Simple deployment
• No external dependencies

Limitations:

• Requires full image rebuild and reflashing for updates

Key Insight

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The method in this article extends the load-type model to support:

• Multiple bootroms
• Multiple kernel images
• Multiple applications

All coexisting on a single disk.

⚙️ Boot Process Overview

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The VxWorks startup sequence proceeds through several stages:

1. romInit

   • Initializes hardware (interrupts, memory, registers)

2. romStart

   • Relocates bootrom to RAM
   • Transfers control to system initialization

3. usrInit

   • Initializes system components
   • Spawns the boot task

4. usrRoot

   • Sets up drivers and system services

5. bootCmdLoop

   • Loads the kernel image

6. sysInit → Kernel Start

   • Transfers control to the VxWorks OS

Default Boot Line Configuration

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Defined in config.h:

Network Boot Example

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#define DEFAULT_BOOT_LINE "fei(0,0) host:VxWorks h=192.168.0.33 e=192.168.0.18 u=user pw=123"

Disk Boot Example

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#define DEFAULT_BOOT_LINE "ata=0,0(0,0) host:/ata0/VxWorks h=192.168.0.33 e=192.168.0.18 u=user pw=123"

🚀 Universal Multi-Image Startup Method

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This solution combines:

• Load-type startup
• DOS 7.1 boot partition
• Batch-driven file switching

It enables menu-based selection of different system configurations at boot time.

🧩 Step 1: Prepare Bootrom, Image, and Startup Script

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Each application configuration includes:

• A dedicated bootrom
• A kernel image
• A corresponding startup script

Modify usrAppInit.c

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Enable automatic script execution:

int fd;
if ((fd = open("/ata0a/startup.txt", O_RDWR, 0644)) != NULL) {
    usrStartupScript("/ata0a/startup.txt");
    close(fd);
}

Ensure the following component is included:

INCLUDE_STARTUP_SCRIPT

Example startup.txt

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id 1,0,"/ata0a/APP/rt.out";
DualNetWork_Switch_OO("198.1.108.1", "198.1.108.253", "255.255.255.0", 66, 0, 0);

id 1,0,"/ata1a/fei.out";
DualNetWorkSwitch("191.8.200.1", "255.255.255.0", "191.8.200.1", 0);

id 1,0,"/ata1a/iiutest";
taskSpawn 0, 100, 0, 0x1000000, main;

Each configuration can use its own version of:

• startup.txt
• Executable binaries
• Bootrom

💾 Step 2: Format Disk with DOS 7.1

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Format the target disk using DOS 7.1 (FAT filesystem).

This ensures compatibility with:

• Boot loader utilities
• Configuration files
• Batch scripts

🖥️ Step 3: Configure Boot Menu (config.sys)

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Define selectable boot entries:

[MENU]
MENUITEM=vxWorks.dbg, start the image
MENUITEM=jk1, JK1
MENUITEM=jk2, JK2
MENUITEM=jk1test, JK1test
MENUITEM=jk2test, JK2test
MENUDEFAULT=vxWorks.dbg,3

[vxWorks.dbg]
DEVICE=c:\HIMEM.SYS
DOS=HIGH,UMB
SHELL=C:\VXLOAD.COM C:\bootrom.dbg

[jk1]
[jk2]
[jk1test]
[jk2test]

🔁 Step 4: Automate File Switching (AutoExec.bat)

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Use batch logic to switch active files dynamically:

@echo off
goto %config%

:jk1test
del bootrom.dbg
copy bootrom.ts1 bootrom.dbg
del D:\APP\rt.out
copy D:\APP\rt1.out D:\APP\rt.out
del test.txt
copy test1.txt test.txt
del iiutest
copy iiutest1 iiutest
goto end

:DOS
goto end

:end

How It Works

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• User selects a configuration from the boot menu
• Script replaces:
  • Bootrom
  • Application binaries
  • Startup scripts
• Bootloader launches the selected environment

🔄 Boot Flow Summary

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1. BIOS completes POST
2. DOS menu appears
3. User selects configuration
4. Batch script swaps required files
5. VXLOAD.COM launches selected bootrom
6. Bootrom loads kernel
7. startup.txt launches application

📊 Key Advantages

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✅ Conclusion

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This universal VxWorks startup method enables true multi-image flexibility using a single storage device. By combining load-type booting with DOS-based menu selection and script-driven file management, it eliminates the need for repeated builds or reflashing.

The result is a highly maintainable and scalable solution where bootroms, kernel images, and applications evolve independently, making it ideal for both development and production environments.