This page is for developers about logging to MMC
it takes complex and CPU-eating software to talk the native MMC protocol (bidirectional data line, CRC ...).
- However most MMC cards support the SPI protocol (possibly all, according to [this useful page] )
- SD is not simpler than MMC, but all SD cards support SPI!
Since we also use SPI for the knock-chip and MCP3208, it was an excellent choice to provide HW support SPI-based MMC on GenBoard/VerThree.
Old thoughts:
For onboard logging (GenBoard/VerThree) we considered the SPI atmel flashes that appear MMC SPI-mode compatible:
- [ http://www.atmel.com/dyn/products/product_card.asp?family_id=616&family_name=DataFlash%AE&part_id=2471 At45DB161B 16Mbit]
- [At45DB321B 32Mbit]
- [At45DB642 is dual interface, big]
- [At45DB1282 is 128Mb version of the above.]
Real MMC is basically the same electrical interface and protocol, but more available and can be removed if a socket is used.
Links
Working system with MMC and ATmega161:
- http://www.myplace.nu/mp3/ under hardware - yampp-7
- http://butterflymp3.sourceforge.net/sw.html AVR plays MP3 from FAT16 stored on MMC
- everything we need for logging to MMC. look at sources/fat...c and mmc...c
- minor cosmetics needed to use non-busy (but interrupt based) reading of SPI data
Basic tech info about hw & sw interface system
Hitachi 16MB MMC-DataSheet as Sample
- http://www.squirrelpf.com/msavr/files/Hitachi16.pdf
- [SPI codee]
- [http://www.vems.hu/files/mmc/mmcsys-version_3-1.pdf
libraries:
- http://www.squirrelpf.com/msavr/files/mmc_eagle_lib_20040112.zip
- http://www.squirrelpf.com/msavr/files/MMCSocket20040111.zip
- http://www.squirrelpf.com/msavr/files/mmpack.zip
Tech sheets
- http://www.conwin.com.tw/multi.htm
- http://homepage.ntlworld.com/seanellis/mmcserial.htm
- http://www.singatron.com/MCC.asp
MMC and SD sources
Can someone check these Toshiba SD flash and comment on them? The question is if we can talk to it via SPI.
- SD-M3203B3
- SD-M6404B3 (1.5 *price of SD-M3203B3)
We would host in WebShop if suitable. Other type is OK, but we want to make sure to be fully compatible with our firmware and HW.
That aside, they are drivable through SPI (sure?)
Official doco appears to need licensed, but there's some limited info here - http://www.sandisk.com/oem/sd.asp
MMC sockets
also digikey has some sockets from HRC
hr845ct-nd $3.80
hr846ct-nd $3.80
Note that the MMC and SD have 7 pins with standard 2.54mm centerline so any card-edge connector should work. Your old 286 ISA motherboard comes to mind with a hammer in the background :-)
See also