MultiMediaCard

MultiMediaCard: Flash memory memory card standard. Unveiled in 1997 by Siemens AG and SanDisk. Free documentation as opposed to SD-Card standard. Which sandisk.com doesn't follow anywayTemplate:Fact.

Local projects

Many projects at OpenCircuits use the MMC protocol to talk to a flash memory card (even when that card is actually a SD card). These include the Minimig Project and many of the Music Player projects.

• the TRAXMOD shows how a ARM can play raw digital audio files streaming off of a FAT formatted MMC/SD Card.
• MMC Card Reader for the dsPic33F

Other wiki

• Wikipedia: MultiMediaCard
• Arduino Playground: Interfacing SD / MMC Card with SPI
• Arduino Playground: reading and writing a SD card

Further reading

• Prototyping Board for LPC2148 apparently connects a LPC2148 ARM processor directly to a SD/MMC card connector without any DOSonCHIP.
• the very small AVR_SD3 development board apparently connects an Atmel AVR directly to a SD/MMC socket without any DOSonCHIP.
• someone ranting about "It's a pet peeve of mine to have SD slots if there's no SD filesystem software. Of the hundreds of DEV boards that have a slot, only a couple have open software to utilize the slot. I'm not sure if the AVR world has this kind of open software?"
• "Embedded SD Card/MMC Card" includes a nice "Comparison of different types of MMC/SD cards", "Competing Formats", and a schematic and PCB for a "Embedded MMC/SD card reader board".
• Reading from SD card?
• the Balloon board apparently has a MMC socket connected to an ARM XScale processor
• "MMC/SD memory cards for Atmel AVR" "This project allows Atmel AVR microcontrollers to read and write ... Multi Media Cards (MMC) and Secure Digital Cards (SD) ... The file system is PC compatible, so that data can be transferred between the two."
• "Atmel AT91SAM9261 Evaluation Kit" with ARM9 (ATMEL AT91SAM9261) connected to MMC/SD socket, and Compact Flash socket
• the "MMC2IEC device": yet another Atmel AVR to SD/MMC card socket. Supports FAT16 and FAT32 support. Oh, and it can also connect to a C64, emulating a Commodore 1541 disk drive.
• ARM7X Development Board includes a MMC/SD socket.
• connecting a JuiceBox to a SD card (also eLinuxWiki:JuiceBoxMMCHack, eLinuxWiki:JuiceBoxUMDCart)
• yet another ARM9 on a credit-card-sized motherboard that includes a SD card slot (and runs uClinux)
• Polyceph Mk.I has complete source code and schematic and PCB files in EAGLE format. Shows how several (?) different processors connect to a SD/MMC card slot
• Evaluation Board for MSP430FG4619 connects that processor to a SD/MMC card connector
• "USB2.0 reference project" "a USB2.0 Card Reader. It support cards such as Compactflash, Memory Stick, Memory Stick Duo, Magic Gate, Secure Digital, MultimediaCard and SmartMedia. The schematic and source code of the reference projects are provided."
• "AVR based USB SD card reader"
• Dosonchip
• The Comp Sys Workbench has 2 projects that demonstrate interfacing to a MMC card (works just as well if you plug in a SD card) ... FAT formatted, but only supports writing a single file in the root directory. Source code can be downloaded free with a "not for commercial use" license. Complete assembled demo boards are available, as well as empty PCBs. The demo boards each include a SDMMC connector, a MCU, and a standard DB9 RS232 connector.
  • PIC+MMC interfacing: one version uses a 18LF2620. The "PIC16F876 to MMC Interface Project" version uses a PIC16F876, which has so little internal RAM that the blocks of 512 bytes required by the MMC protocol are buffered in a Ramtron 64kbit FRAM.
  • "AVR SD3": SDMMC socket, Atmel AVR163L, (also works with most other 40 pin AVR-L mcus: Mega16L, Mega32L, etc.)
• "How to Use MMC/SDC" has some useful tips for adding SDMMC to small embedded system (examples uses ATmega64 @9.2MHz). Has detailed bit-by-bit timing diagrams.
• "Open source software for FAT file system over MMC SDC" by allankliu 2008 mentions several source code libraries for reading and writing to FAT-formatted files on MMC/SD cards: EFSL (Embedded Filesystem Library) has been ported to TI TMS C6000 DSP, Atmel ATmega, and NXP ARM LPC2103; FF/TFF (FatFile and TinyFatFile) has been ported to Atmel ATmega, Renesas H8, Microchip PIC24F; NXP Arm LPC2000, TI MSP430, and other processors; and uC/FS (a component of uC/OS-II) has been ported to several processors.
• "Data storage, A/D and D/A conversion" by Indrek Mandre. Describes interfacing a Atmega168 to a 1GB SD card (using PC compatible FAT16) and to a 4GB SDHC card (using PC compatible FAT32).
• F. Foust. "Secure Digital Card Interface for the MSP430"

FIXME: consider making this page about "how to interface a microcontroller to a SD/MMC card"?