NET+OS Bootloader

1. NET+OS Bootloader • Overview • Requirements • How to Build • How to Customize • Changes to Applications • Configuration Settings

2. 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

3. 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

4. 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

5. 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

6. Requirements • DHCP or BOOTP Server • TFTP Server • TFTP must be on the same machine as the DHCP/BOOTP server

7. 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

8. 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

9. 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

10. How to Build for MicroCross • Configure the BSP • Build the BSP • Build “make all” in the bootloader directory

11. 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

12. Example static char *getDefaultFilename(void) { static char *defaultFilename = ""; return defaultFilename; }

13. 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

14. Change Error Reporting • Default implementation blinks LEDs in a pattern to indicate error condition • Edit reportError() to change this

15. 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()

16. 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()

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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>]

23. 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

24. Default Boothdr Config File WriteToFlash Yes Compressed Yes ExecuteFromRom No flashOffset 0x10000 ramAddress 0x800000 MaxFileSize 0xD0000

25. 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.

26. 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