SD card read/write with Arduino

now is there no way because the arduino isnt currently capable (ie not part of the core code) if thats the case could a custom core be written.

or is there no way because of the technical limitations of the chip and execution enviroment?

and why limit it to fat if raw works fine?

and why limit it to fat if raw works fine?

Because raw is difficult to deal with if you want to pop the SD card out of the arduino and put it into a computer to exchange data. If you use FAT on the SD card, you already have FAT filesystem drivers on all major operating systems. If you use some raw format, you must write custom code for every possible operating system that you wish to exchange data with.

-j

If we could store the code on the SD card then could we make it able to have 2 sets of code files and a switch to switch between them and their code?

AVR 8-bit microcontrollers are (modified) harvard architecture. that means that the program and data memory are completely separate except for the special ability to load program data into ram such as string constants, so you can't load anything into ram then run it as if it was code, like you can on von neumann architectures such as desktop PCs.

This basically means that we can only use SD for data. If you want to store code on one, you will have to write your own language and interpreter, or use a microcontroller with a von neumann architecture instead of the atmega168 on your arduino.

Sorry, Triffid, but as I said the ATmega is capable of self-programming, so yes it is technically possible for it to pull code from the SD card, write it to flash, and execute it. This really isn't any different conceptually from pulling the data from a serial port and writing it to flash, which is exactly what the Arduino bootloader does for us, allowing us to program the ATmega without a hardware programmer.

As I said earlier I don't think it's terribly practical, but it absolutely is possible.

-j

So back on topic... SD mode IO? SDHC support?

ducttapepro6---

I do also experience som trouble after resetting Arduino. Everything works fine to read and write to the SD Card but after resetting the Arduino the SD Card data is blank.

Have you found any solution for this?

//Daniel

Zumbi, I am having the same problem as you. I cannot get the SD card to initialize. If anyone has some pointers I would be grateful. : ::slight_smile:

Is it possible to change the Arduino pins that are used by the library? I can't seem to find any reference to the pin numbers in the library source code.

Thom

EDIT

I've found out you need to use the SPI pins, so cannot change the pins in use by the SD card reader... time to get rewiring :smiley:

Hi everyone,

Earlier, ducttapepro6 wrote:

Mr. Orange-

I had no trouble getting your code up and running in 15 minutes - happily logging, saving, and reading the input to analog1.

However, after hitting the arduino reset button, I found that the read function returns junk(from the SD card).

Shouldn't the SD card retain data after a power cycle? or, is it a function of the code that you so nicely supplied to get me started - and I just don't understand it, yet?

Along with Daniel, I'm hoping that someone can explain why the card starts up with the same junk data each time, if the first thing I do when the sketch runs is hit 'r'.

agent_orange says that it's like having a 1G (or whatever) EEPROM, which is IDEAL for my situation. My arduino will be sitting in a box, on top of a pole, powered by a solar panel for up to 3 months at a time. I have it successfully writing the date and max & min temperatures to the EEPROM, which I can read back out as desired. The EEPROM data is only overwritten after a new sketch is started. This is the functionality that I require from the SD card, but the supplied code appears to wipe the card each time the sketch is started. (I tried commenting out the if(!sd_raw_init()) but that didn't help).

agent_orange, thanks so much for supplying this work, it's fantastic & there's no WAY that I'd be able to work this out on my own. But if anyone can show me a way (even if it's a seperate sketch) to access the data on the card without destroying it, it would be GREATLY appreciated!!

I guess the other option would be if someone could recommend a Windows-based program which could access the data on the SD card?

Thanks for reading everyone!!

I am using the same simple logging code that you have posted with just the raw read and write. The initialization seems to go fine, and then it acts like it is reading and writing even when i have the SD card removed from the slot. I enter the 'r' command, and it prints the same info, not zeros or junk. when i reset, it loses the info. It is as if it is just storing it in on board memory until it resets, like it isn't even using the sd card at all, and then loses the data when it resets.

Any ideas?

PS...
Thank you Agent Orange for working on this project.

Same here... at first it looks like it's working fine, it appears I can sample data to the card and read it back. But once I've reset the board and try and read the data back I am presented with all zero's. :frowning:

I too can confirm that reading and writing appears to work even without a card in the slot, despite the fact that it says initialisation failed and doesn't show any card statistics. :-/

With a card in the slot I get reasonable looking card statistics (size: 125698048 for a 128MB card) which suggests it can see the card.

Which again raises the question, what are we missing here? Any ideas?

I will be sure to post if I make any further discoveries.

Thanks all! :slight_smile:

Hi there.

I found another solution that I think is much better for storing large amount of data and it is Fat16+32 compatible. You can communicate with the card with normal serial, read more: http://www.roguerobotics.com/ uMMC datastorage.

Regards /Daniel :slight_smile:

Hi Daniel,

That's certainly a nice-looking solution! Might be a bit of overkill for me though; using a 16Mb SD card that came with my camera, I worked out that if I store 10 bytes of data every minute, I've got over 2.5 YEARS worth of storage capacity...

Just for my curiosity, how would you communicate with this uMMC device? I'm guessing that you'd have to Serial.print() commands like "O 1 R /LOGS/JANUARY/JAN03.LOG{cr}" to it in it's own language?

Thanks!

Okay, I am getting somewhere...

I thought I would try the uFat library that was mentioned fairly early on in this thread, which straightaway gave me a directory listing of all the files on this card. But hang on a minute, I thought I had formatted the card! So I popped it back into the computer, deleted all the files and created the required data.bin file, but to my amazement my new file disappeared and all the old ones came back! No amount of deleting formatting or mortifying seemed to affect this card any more, so I have scrapped it and got myself a new one.

uFat seemed very temperamental with my new card, failing to initialise nine out of 10 times. I put a simple loop round the initialising statement with a delay, so it would retry if it failed instead of just showing an error and halting. This seemed to work a treat, no matter how much delay before or after it always seems to fail once and then initialise fine on the second attempt without fail. Reading and writing then worked perfectly :smiley:

I think I am going to stick with uFat over the raw library as it isnt any bigger and I still can't get the raw library to work even with my new card (same problems as described before), also I like being able to read my data back on the computer. :slight_smile:

The only downside is that the code for using uFat isn't as friendly as the raw library, and I can't seem to get it to write one byte at a time, it has to be written in 512byte sectors, but I can live with this.

Hopefully this information helps someone out, I am thinking to get the raw library working perhaps something needs to be inside a retry loop much like I had to do with the uFat library to get it working.

Thanks everyone who has contributed, especially agent_orange for the circuit diagram (which needs no modification to work with uFat), and sirmorris for the uFat library.

Hey bobemoe this sounds good. I've tried the RAW program and haven't had any luck. I'm currently attepmting SirMorris's code and am not getting anywhere there either. I get some errors when I try to compile.

o: In function microfat::initialize(unsigned char*)': multiple definition of microfat::initialize(unsigned char*)'hardware\libraries\uFat\microfat.o:C:\arduino-0010/hardware\libraries\uFat\microfat.cpp:17: first defined here

o: In function microfat::locateFileStart(char const*, unsigned long&, unsigned long&)': o: In function main':

Any sugggestions?
I have the required header files and I'm trying to run the microfat program.

My apologies if this has already been resolved somewhere else :sunglasses:

Hi smelios,

It doesn't look like you are using the latest version, try downloading uFat2.zip rather than mmc1.rar, hopefully that will fix the problem.

Fresh code mmmmmm.

Still having problems. Bobemoe, did you encounter an error like this?

error: 'directory_entry_t' was not declared in this scope In function 'bool showDirectory_walkerfn(directory_entry_t*, unsigned int, void*)':
In function 'void showDirectory()':

Or did yours compile with no problems?

Sorry to keep asking you questions i'm a noob. ;D
Your help is greatly appreciated!

Mine compiled fine.

I can get a similar error if i remove the #include lines from the top of the example which makes me think its a problem with your includes.

Did you delete the files you copied to /hardware/libraries/ for version 1? they may be conflicting.

Found my error, I was on arduino10. Morris said he developed this in Arduino12 so i downloaded that and it complied. Now i just can't init the sd card. Oh well work for another day :stuck_out_tongue:
Thanks again for helping