Bootloading from SD card

eeboy · 2009-11-16T04:57:56+00:00

I want to enable my device to replace the contents of flash by reading in abinary file from the SD card. The catch is that I don't want to implementFAT in my bootloader. I want it to be as small in size and as simple as canbe. The vast majority of the users will be running windows. The binary file(representing the new flash contents) does not have to be placed on the SDcard by conventional methods (dragging the downloaded file from hard diskto SD in explorer). I can force the user to place the file onto the SD cardusing the application used to configure the device. Another constraint isthat the SD card format (FAT) must be left alone as the user needs to readand write files that the device has generated. So, how can I write thisfile to the SD card from a windows based machine such that my device canread the firmware without knowing anything of FAT (yet FAT is still presenton the card)?Hopefully the problem makes sense... :) --------------------------------------- This message was sent using the web interface on

C

Chris Giese 16 years ago

I also did a FAT-12 PC bootsector in 512 bytes:

formatting link

This code requires that the second stage or kernel or whatever be in the root directory, but it need not be physically contiguous on the disk.

FAT-16 wouldn't be too different, but I agree that a FAT-32 bootloader probably wouldn't fit in 512 bytes.

Vote

A

ArarghMail911NOSPAM 16 years ago

13 vs 5 instructions for FAT12 vs FAT16 in the code I wrote.

No, I don't think it's even possible, but I haven't tried.

And see no point doing so, either. :-)

ArarghMail911 at [drop the 'http://www.' from ->] http://www.arargh.com BCET Basic Compiler Page: http://www.arargh.com/basic/index.html To reply by email, remove the extra stuff from the reply address.

Vote

A

ArarghMail911NOSPAM 16 years ago

Forgot to mention that I cheated and just copied the first 64k worth of FAT to memory. For FAT12, that handles the split across sectors headache.

ArarghMail911 at [drop the 'http://www.' from ->] http://www.arargh.com BCET Basic Compiler Page: http://www.arargh.com/basic/index.html To reply by email, remove the extra stuff from the reply address.

Vote

Bootloading from SD card

Join the Discussion

Didn't find your answer?