Wrong image format for "source" command

I’ve got a version of RISC OS that boots and reads a CMOS file in from an SD and an MMC card, but when I try the same set of files on a 4 GB SDHC card, I get this debug output:

mmc1 is available
reading boot.scr

120 bytes read
Running bootscript from mmc ...
## Executing script at 82000000
Wrong image format for "source" command
OMAP3 beagleboard.org #

Can anyone give me a clue as to what’s going wrong, please?

The files have been written using Fat32Fs.

It turns out that what was read back from the card was very different from what was written to the card. The boot.scr file bore no relation to the one I wrote. I repeated the deletion and writing operations, with the same results – dismounting at appropriate times, of course.

I have had to reformat the card to get it to work at all sensibly.

(Now I just have to fix my code; although RO boots up, my code looks in the wrong place for the root directory.)

Hi Dave,

you know you have to look at different places for it depending on the format of de SD card. FAT12/16 have a Root Directory but FAT32 doesn’t.

you know you have to look at different places for it depending on the format

Absolutely. That wasn’t the problem; I could write to the SDHC card (using Fat32Fs and a SanDisk SDHC reader/writer), dismount it, mount it, and read back (still using Fat32Fs and the SanDisk reader/writer) something other than what was written. On some occasions the “riscos” file was missing.

I am getting the impression that Fat32Fs needs to have its devices dismounted more than once to get all its cache flushed to the device.

Anyway, I now have code that works for SD, SDHC and MMC, any of which can be in FAT16 or FAT32 format. I still have to add code for FAT12. I also need to read the complete cmos file out – I need to check that it continues to work if the file occupies more than one cluster. Some error handling might be a bonus. Then we would be ready to merge.

FAT12/16 have a Root Directory but FAT32 doesn’t.

They all have a root directory, but not necessarily in the same place – though I think they usually are… for FAT12/16, it’s in a fixed number of blocks immediately after the last FAT; for FAT32, it starts in a cluster, habitually cluster 2, which is immediately after the last FAT.

Yes, you are right. In my code I look for the root directory in FAT12/16/32 at 'StartOfPartition + Reserved Sectors + SectorsPerFat*2'. With Reserved Sectors the 16 bits at address 0×0e.