Post by thread:RES: [PIC] Sd card interface

i have been searching around for good place to learn about the sd card SPI interface. i will be writing this in asm and i hope to even implement the use of the fat16 file system. so i may be able to read a file on the pic that was written on the pc and vise versa. i am having a hard time even finding the a good pic interface. any help would be appreciated. -- View this message in context: www.nabble.com/Sd-card-interface-tp18579174p18579174.html Sent from the PIC - [PIC] mailing list archive at Nabble.com.

Hi, I have this link bookmarked: http://www.captain.at/electronics/pic-mmc/ Basically, you'll want to use the MMC interface, but this is also implemented by SD cards (at least for those <= 2GB, not sure about SDHC). This is in C, but it might be good enough. Regards, - Marcel On Mon, Jul 21, 2008 at 3:47 PM, threewheeler7 <spam_OUTthreewheeler7TakeThisOuThotmail.com> wrote: {Quote hidden}> > i have been searching around for good place to learn about the sd card SPI > interface. i will be writing this in asm and i hope to even implement the > use of the fat16 file system. so i may be able to read a file on the pic > that was written on the pc and vise versa. i am having a hard time even > finding the a good pic interface. any help would be appreciated. > -- > View this message in context: > www.nabble.com/Sd-card-interface-tp18579174p18579174.html > Sent from the PIC - [PIC] mailing list archive at Nabble.com. > > -

Microchip has a library which may be of use to you: http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en532040 AN1045 - Implementing File I/O Functions Using Microchip's Memory Disk Drive File System Library "This application note covers the usage of file I/O functions using Microchip's memory disk drive file system library. Microchip's memory disk drive file system is based on ISO/IEC 9293 specifications. It is also known as the FAT16 file system, and used on earlier DOS operating systems by Microsoft Corporation. The included source code also supports the FAT32 file system. This is the most popular file system with SD cards, CF cards and USB thumb drives. The applications note code is designed to run on 8-bit PIC18 devices and all 16-bit devices (PIC24F, PIC24H, dsPIC30F, dsPIC33F)." Cheers, Zik On Tue, Jul 22, 2008 at 8:47 AM, threewheeler7 <.....threewheeler7KILLspam@spam@hotmail.com> wrote: {Quote hidden}> > i have been searching around for good place to learn about the sd card SPI > interface. i will be writing this in asm and i hope to even implement the > use of the fat16 file system. so i may be able to read a file on the pic > that was written on the pc and vise versa. i am having a hard time even > finding the a good pic interface. any help would be appreciated. > -- > View this message in context: > www.nabble.com/Sd-card-interface-tp18579174p18579174.html > Sent from the PIC - [PIC] mailing list archive at Nabble.com. > > -

I've used this library, and it works! It's pretty easy to configure (just select SPI port and slave select). Harold {Quote hidden}> Microchip has a library which may be of use to you: > > http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en532040 > > AN1045 - Implementing File I/O Functions Using Microchip's Memory Disk > Drive > File System Library > > "This application note covers the usage of file I/O functions using > Microchip's memory disk drive file system library. Microchip's memory disk > drive file system is based on ISO/IEC 9293 specifications. It is also > known > as the FAT16 file system, and used on earlier DOS operating systems by > Microsoft Corporation. The included source code also supports the FAT32 > file > system. This is the most popular file system with SD cards, CF cards and > USB > thumb drives. The applications note code is designed to run on 8-bit PIC18 > devices and all 16-bit devices (PIC24F, PIC24H, dsPIC30F, dsPIC33F)." > > Cheers, > Zik > > On Tue, Jul 22, 2008 at 8:47 AM, threewheeler7 <threewheeler7KILLspamhotmail.com> > wrote: > >> >> i have been searching around for good place to learn about the sd card >> SPI >> interface. i will be writing this in asm and i hope to even implement >> the >> use of the fat16 file system. so i may be able to read a file on the pic >> that was written on the pc and vise versa. i am having a hard time even >> finding the a good pic interface. any help would be appreciated. >> -- >> View this message in context: >> www.nabble.com/Sd-card-interface-tp18579174p18579174.html >> Sent from the PIC - [PIC] mailing list archive at Nabble.com. >> >> --

i do beleve that the mmc interface is the SPI interface, am i correct? Marcel Birthelmer wrote: {Quote hidden}> > Hi, > I have this link bookmarked: http://www.captain.at/electronics/pic-mmc/ > Basically, you'll want to use the MMC interface, but this is also > implemented by SD cards (at least for those <= 2GB, not sure about SDHC). > This is in C, but it might be good enough. > Regards, > - Marcel > > -- View this message in context: www.nabble.com/Sd-card-interface-tp18579174p18579734.html Sent from the PIC - [PIC] mailing list archive at Nabble.com.

On Mon, 21 Jul 2008 15:47:52 -0700 (PDT), "threewheeler7" <.....threewheeler7KILLspam.....hotmail.com> said: > > i have been searching around for good place to learn about the sd card > SPI > interface. i will be writing this in asm and i hope to even implement the > use of the fat16 file system. so i may be able to read a file on the pic > that was written on the pc and vise versa. i am having a hard time even > finding the a good pic interface. any help would be appreciated. One trick made popular by a piclister avoids the filesystem firmware requirement by creating one big blank file on the card(using a PC) and then treating it like your own private play area. That way the PIC doesn't have to deal with the FAT file system at all. Just use your own delimiters within the file itself. Cheerful regards, Bob -- http://www.fastmail.fm - Access all of your messages and folders wherever you are

On Mon, 21 Jul 2008 16:35:55 -0700 (PDT) threewheeler7 <EraseMEthreewheeler7spam_OUTTakeThisOuThotmail.com> wrote: > > i do beleve that the mmc interface is the SPI interface, am i correct? Yes... And just to point out the largest stumbling block: all of the filesystems use 512-byte 'sectors'. So you need a PIC with at least 512 bytes of memory to store one complete sector (which is why all the references point to the larger PICs). The only exception, is that you could only partially write each sector, and then use some program in the PC to put it all together. As far as I know, that limit is part of the SD norm, and not changeable. John

John Coppens wrote: > > > filesystems use 512-byte 'sectors'. So you need a PIC with at least 512 > bytes of memory to store one complete sector (which is why all the > references point to the larger PICs). > > if i need to write smaller files cant i just write it and tell the pic to add appropriate zeros to finish off the sector? -- View this message in context: www.nabble.com/Sd-card-interface-tp18579174p18581959.html Sent from the PIC - [PIC] mailing list archive at Nabble.com.

Bob Blick-4 wrote: > > One trick made popular by a piclister avoids the filesystem firmware > requirement by creating one big blank file on the card(using a PC) and > then treating it like your own private play area. That way the PIC > doesn't have to deal with the FAT file system at all. Just use your own > delimiters within the file itself. > > Yes Bob i actually thought of doing something like that, but i would like to be able to read a file made by a pc a little easier rather than having to put a specific text string in the file for the pic to look for. -- View this message in context: www.nabble.com/Sd-card-interface-tp18579174p18582038.html Sent from the PIC - [PIC] mailing list archive at Nabble.com.

On Mon, 21 Jul 2008 21:05:05 -0700 (PDT) threewheeler7 <threewheeler7spam_OUThotmail.com> wrote: > if i need to write smaller files cant i just write it and tell the pic > to add appropriate zeros to finish off the sector? Yes... Eg. you could only write 128 'data' bytes, and fill the rest with anything. On the PC you'd have to read only the first 128 bytes. But if you want to write several files, you'd have to manage the directory too, which complicates the software a lot. Easier to pre-write a large file, then fill it with partial sector. Sort of making your mini-filesystem inside a large file. John

On Mon, 2008-07-21 at 21:03 -0300, John Coppens wrote: > On Mon, 21 Jul 2008 16:35:55 -0700 (PDT) > threewheeler7 <@spam@threewheeler7KILLspamhotmail.com> wrote: > > > > > i do beleve that the mmc interface is the SPI interface, am i correct? > > Yes... And just to point out the largest stumbling block: all of the > filesystems use 512-byte 'sectors'. So you need a PIC with at least 512 > bytes of memory to store one complete sector (which is why all the > references point to the larger PICs). > > The only exception, is that you could only partially write each sector, > and then use some program in the PC to put it all together. > > As far as I know, that limit is part of the SD norm, and not changeable. You are correct, however you don't necessarily need a PIC with 512bytes of RAM to get things going. For my carmon project http://repatch.dyndns.org:8383/pic_stuff/carmon I used a 32kB I2C EEPROM for sector storage on a 877. Works to this day perfectly. TTYL