One SD card - 2 cpu's

nicofer · Joined: 01 May 2013 Posts: 90 Location: GRJ

Hi

This might not be the correct topic but is has to do with SD cards.

I want to share one SD card between 2 cpu s - one a m128 - other a 328 maybe .

The plan is for the mega128 to use the card for date store and so on most of the time

Second cpu will need to control the main pcb and card to put in in a standby state while it access the card - to save a new

flash file for bootloader if required received over GPRS or some other remote communication channel .

I have not tested any of the hardware but I think it should work with a few 4066 or same type of isolators on the spi lines .

The slave cpu will also control main cpu RESET and a " bootloader activation " pin and access to the SD card .

Maybe it is old technology so any new ideas on this setup ?

Cheers

oe9vfj · Joined: 17 Jun 2004 Posts: 269 Location: Austria, Hard

Only one CPU can use the Card at the same time.
You can give the control of the card from one CPU to an other CPU, if all opened files are closed and do an additional FLUSH to be sure, the FAT and directory is updated anyway.
IF you make sure, that all information is written to the card and all files are closed, like you want to remove the card to put it to an other system, you can give the control to an other CPU.