Joined: 25 Jul 2007 Posts: 284 Location: PA near Philly
Posted: Tue Aug 18, 2009 2:19 am Post subject: Reading/writing a 512 byte blocks with a MMC/SD card
Josef,
Is it possible to use just the lower level MMC/SD read & write routines without the full FAT routines? I would like to be able to read/write the 512 byte blocks and save all the program space that the fat routines use up.
You can use Drivereadsector and Drivewritesector to read and write arbirtary sectors into/from a 512 byte array. This is handy if you just want to write a single massive stream of data (eg data logger).
You will destroy any FAT/FAT32 formatting on the card if you simply write sectors starting from 0, but it's a very easy way to get massive storage space. You can perhaps use EEPROM or the first sector on the card to store a simple table of how many sectors you've written to.
You can read this data into a PC if you use a low-level disk reader/editor (hex editor) such as the free DiskImage.
Code:
Dim Berror AsByte Dim Abuffer(512)asByte' Hold Sector to and from SD Card Dim Wsrampointer AsWord' Address-Pointer for read/write Dim Lsectornumber AsLong' Sector Number
' give Address of first Byte of the 512 Byte Buffer to Word-Variable
Wsrampointer =Varptr(abuffer(1))
' Set Sectornumber
Lsectornumber =0
' Read in sector from card
Berror =Drivereadsector(wsrampointer , Lsectornumber)
'Hex dump of sector For I =1To512 PrintHex(abuffer(i)); Next I
' Now write buffer to another sector on card
Lsectornumber =1
Berror =Drivewritesector(wsrampointer , Lsectornumber)
_________________ If all else fails, read the manual. Even better: read the manual before something fails. If you can't find it in the manual, search the forum.
BascomAVR 2.0.8.2
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