Storage media for micro controllers

AdrianJ · Joined: 16 Jan 2006 Posts: 2477 Location: Queensland

All those types can be used with AVR processors. Depends whether you want to access the data also with a PC, which is easiest.

If you use AVR internal EEPROM, you can only access directly with the AVR, but of course you can read and write from there to a serial port, and read that with a PC.

Similar with dataflash on board, although you could of course provide external connections and access those with a PC and suitable program and hardware. Dataflash can use the SPI bus.

MMC ( now mostly SD ) cards are similar to dataflash, but can be plugged in to either the AVR host, or a PC card reader. You can add AVR-DOS filesystem to bigger AVRs. You need at least 1Kb of internal SRAM for buffers, and read and write files using Bascom which you can directly use with a PC. See the AVR-DOS forum for much discussion.

Forget memory sticks, these use USB and need a USB host to work with. Only a PC is suitable for this, its far too difficult to do with an AVR, and even with the AVR USB host chips, its still a lot of work.

Another option is ferro-ram for Framtron. Similar to dataflash, but has essentially unlimited write cycles. Versions are available for both SPI and I2C bus connection.

Mostly it boils down to how much data you want to store. A few hundred bytes or so for internal EEPROMS. Several KBytes to a few MB for dataflash, up to several GB for an SD card.

POTOOLE64BAS · Joined: 08 Nov 2008 Posts: 56 Location: North Dakota, USA

AdrianJ stated

AdrianJ · Joined: 16 Jan 2006 Posts: 2477 Location: Queensland

When you say you want to store the data in a remote location, how do you want to access it ? Can you take a PC ( eg laptop ) to there, connect it to a serial port, and download the data ? Or is it only possible to recover an SD card, and read it later from a PC ?

If you can get serial access, then you can use anything you like as the data medium. The AVR can handle both storing the data on the media, and recovering it to send to a PC in any serial method you like.

If you want to use SD or similar cards, and you want a filesystem a PC can read, you must use at least AtMega64 or bigger, to get enough RAM for the AVR-DOS filesystem. Yes you can write directly to the card as physical sectors with a smaller processor, but then you need special software on a PC to recover the data.

Same would apply to dataflash on some sort of carrier. As I said, dataflash uses the SPI bus. You would need special hardware and software on the PC end to read it, rather than just a freely available card reader.

A further possibility is to have a cell-phone modem at the remote end, and send the data via SMS messages, or similar.

AdrianJ · Joined: 16 Jan 2006 Posts: 2477 Location: Queensland

Also look at Ben Zilstras post in:

http://www.mcselec.com/index2.php?option=com_forum&Itemid=59&page=viewtopic&t=6793

VDIP modules have made using USB memory sticks a lot easier, and relatively cheap.