NET+OS Bootloader

• Overview

• Requirements

• How to Build

• How to Customize

• Changes to Applications

• Configuration Settings

Features

• Recovers when flash update fails

• Application image is compressed

• Uses DHCP or BOOTP to get an IP address

• Uses TFTP to download new firmware

Normal Operation

• Bootloader always runs at Power Up

• Uses standard BSP initialization code

• Performs 32-bit CRC checksum of application image

• Decompresses Application from flash to RAM

• Starts Application

Recovery Mode

• Triggered if Application Image fails CRC checksum

• Uses DHCP/BOOTP to get an IP address

• Uses TFTP to download a new application Image

• Writes application image to flash

• Resets the unit

Structure of Flash ROM

• Bootloader stored in first 64K of flash

• Last sector of flash may be used for NVRAM storage

• Rest of flash is used to hold application image

• Customers can create more sections

Requirements

• DHCP or BOOTP Server

• TFTP Server

• TFTP must be on the same machine as the DHCP/BOOTP server

DHCP/BOOTP Server Setup

• Must supply boot filename, which is used as the name of the firmware image to download

• Bootloader will reject offers that don’t have a boot filename

• Must also supply an IP address

• Should supply a gateway and subnet mask

Lock Bootloader Sectors

• Booloader image must be written into start of flash at the factory

• Sectors that contain the bootloader must be locked at the factory to prevent accidental erasure

• Lock method depends on flash part

How to Build for Green Hills

• Configure the BSP

• Build the BSP

• Build the RAM image of the bootloader

• Build the ROM image of the bootloader

• Bootloader is in netos\src\bootloader

How to Build for MicroCross

• Configure the BSP

• Build the BSP

• Build “make all” in the bootloader directory

How to Customize

• Customization hooks in customize.c

• Customize.c contains a default implementation of the bootloader

• Custom features are added by modifying functions in customize.c

• These functions were written to be easy to customize

Example

static char *getDefaultFilename(void)

{

static char *defaultFilename = "";

return defaultFilename;

}

How to Change default Filename

• Default filename is sent to DHCP/BOOTP server as a hint about what file the unit wants to download

• Standard implementation is to send an empty string

• Change getDefaultFilename() to supply a default boot filename

Change Error Reporting

• Default implementation blinks LEDs in a pattern to indicate error condition

• Edit reportError() to change this

Determine when to Update Image

• Default implementation is to update the image if it fails a 32-bit CRC checksum test

• Might want to look at buttons or switches too

• Change shouldDownloadImage()

Determine if Image is Valid

• Need to determine if image downloaded from TFTP server is valid

• Default implementation performs a 32-bit CRC checksum of it

• Might need to prevent users from upgrading cheap units with firmware from expensive ones

• Edit isImageValid()

Might not want to use DHCP

• Default implementation uses DHCP/BOOTP to get an IP address and name of TFTP image to download

• Might want to get this information in a different way

• Can change downloadImage() to do this

Exchanging Additional Information

• May want to send additional information to the DHCP server, or have it send additional information to the unit

• Can customize downloadImage() to send Vendor Class ID (60) to DHCP server

• DHCP server can send Vendor Info (43) to unit

Changes to NAFTPAPP

• NAFTPAPP looks at filename to determine where to write image into flash

• Image.bin is written into application image space in flash

• Rom.bin is written to start of flash

Changes to Applications

• Debug, romzip, and ramzip images are gone

• The “Image” image replaces all of them

• Creates debug version that corresponds to the image the bootloader will execute

• Also creates compressed version that can be written to flash and executed by the bootloader

Structure of Application Image

• Image that is written to flash has a header

• Header is created by boothdr.exe

• Image is usually compressed

• Generated automatically when “image” is generated

Boothdr.exe

• Used to generate image that is written to flash

• Adds header and 32-bit CRC checksum

• Compresses application image

boothdr <config> <in> <out> [<custom header>]

Boothdr Config File

• Used to set values in bootloader header

• Default version stored in linkerScripts\bootldr.dat

• Customers can override this by editing build or make files to use a different one

Default Boothdr Config File

WriteToFlash Yes

Compressed Yes

ExecuteFromRom No

flashOffset 0x10000

ramAddress 0x800000

MaxFileSize 0xD0000

Customized Headers

• Customers can append their own headers onto the bootloader header

• Useful for identifying the H/W requirements of the firmware

• Custom header is appended by adding the name of a header file onto the command line used by boothdr.

New BSPCONF.H Settings

• BSP_BOOTLOADER_SIZE determines the size of the bootloader image in flash

• BSP_APPLICATION_OFFSET determines where the application image starts in flash

• BSP_APPLICATION_IMAGE_SIZE determines the maximum size of the application image in flash