SD Max card - does it use SPI protocol or full SD card protocol?
ElectricAye
Posts: 4,561
Greetings,
I would like to know if the Hydra SD Max card system uses the SPI protocol for SD cards or if it uses the "full" SD card protocol. I looked at the sample manual for the SD Max card, but it doesn't provide the section beyond a description of the SPI protocol. It mentions the use of an SD Max driver but it doesn't tell which protocol it uses, so I'm wondering if a 2GByte SD card will be able to store 2Gbytes or if the SD Max driver limits what can be done.
thanks,
Mark
I would like to know if the Hydra SD Max card system uses the SPI protocol for SD cards or if it uses the "full" SD card protocol. I looked at the sample manual for the SD Max card, but it doesn't provide the section beyond a description of the SPI protocol. It mentions the use of an SD Max driver but it doesn't tell which protocol it uses, so I'm wondering if a 2GByte SD card will be able to store 2Gbytes or if the SD Max driver limits what can be done.
thanks,
Mark
Comments
The 2GB SD card size limitation is that of the FAT16 file system, not the card protocol. Microsoft has patent claims on both the long file name FAT16 file system and the FAT32 file system and requires licensing fees for their use. I know these are used in Linux, but I'm not sure how that's done with the licensing issues.
Post Edited (Mike Green) : 8/28/2008 3:50:28 PM GMT
Thanks again. At your suggestion, I placed an order for this Hydra SD Max card so I could learn about SD cards, but while I'm waiting on the package, I'm plowing through the SD Card association's simplified spec. So thanks to your reply, I now know to focus on how the SPI works.
peace,
Mark
Trust me you don't want to mess with the parallel SD protocol, also, the SPI protocol is more than fast enough for any use. However, if you want to write a driver for the parallel mode you can, but the protocal is licensed and to use it legally in products you have to buy a license, so that's why everyone uses the SPI protocol. And like Mike said, you don't have to use Fat16, its just a layer on top of the SD protocol, you can write your own disk system, linux, etc. the SD cards have no idea about file systems, they are more or less just an array of sectors, that's it, very simple.
When you do get your SD max, I highly recommend you read my eBook on the subject about 85 pages of really "what you need to know" information about how all of it works from the electrical spec, to SPI protocol, to the SD protocal, to the FAT16 file system.
Andre'
thanks for the advice. I ordered the SD Max card specifically to get the manual since I couldn't find anything else on the internet or elsewhere that walks me through the world of SD cards step by step. The sample pages you provided seem to be at the right level for me, so I'm looking forward to getting my hands on the rest of it. My need for storing data doesn't require high speed or anything fancy so the SPI mode is all I'm concerned with.
cheers,
Mark