Not really electronics at this stage, I'm writing the software to bit-bang data out of an SD card on Dirac. I have finally managed to extract a bit of boot sector off an SD card, a feat not entirely dissimilar to what I did with the floppy drive:
EB 00 90 20 20 20 20 20 20 20 20 00 02 20 01 00 02 00 02 00 00 F8 7B 00 3F 00 10 00 E9 00 00 00 17 43 0F 00 80 00 29 10 4A 73 18 4E 4F 20 4E 41 4D 45 20 20 20 20 46 41 54 31 36 20 20 20 00 00
There were a few little embarassing moments along the way. Like when I didn't seem to be getting any comms from the card, only to find it wasn't pushed properly into the adaptor. Or the bit where I could see the boot sector on the card from my laptop, but when I tried to read the first sector from Dirac I got zeros. Hmmm. I tried reading the second sector. I got 0xFFs. Weird. I think hard, I realise that on the Mac I'm reading the first sector of the partition. Checking the first couple of sectors of the disk, my reading has been correct. A few mistakes later, and I've finally got the data of the boot sector of that partition.
While this guide and this page have been useful, having simple, readable code to demonstrate how to do it has been really helpful.
Posted 2016-06-17.