accessing a text file using PIC

[aashasurendran]

Is it possible to open a text file using pic?

[bkamen]

Do you mean from a storage device like an SD/CF card? or maybe a USB stick? Formatted in FAT or FAT32 or maybe NTFS or EXT3?

Or over a network from a server as a client?

Maybe it's stored in a compressed format on a I2C or SPI attached EEPROM?

Please, we need more information if we're to help.

-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D

[aashasurendran]

Actually I'm a beginner of PIC. Can we use the function like fopen() fclose() etc (), to access a file which stored in harddisk?

[bkamen]

Ahh, I see where you're coming from now.

Imagine an Intel/AMD CPU. It's general purpose processor that sits in a box like the one you're using to probably surf this forum.

Now, imagine an embedded 32bit CPU like the one running "under the hood" (or LCD) of your PalmPilot or WindowsCE/Mobile phone or iPod.

Now imagine the kind of CPU that might be in a custom weather sensor or maybe the one controlling the the LCD via USB on your computer or maybe running the control panel on your fridge's ice maker/water dispenser.

THAT is something a PIC (well, for a lot of us) might do. Anything which might need some smarts but without windows or linux running on it.

Maybe some sensors in your car. Maybe running the ignition in your car. Or maybe the fuel flow in my airplane. My Fluke multimeter doesn't have Windows running on it. The user interface is a bunch of buttons and a VFD. THAT's a PIC application.

Now, if you REALLY wanted, you could probably get a 16bit PIC (PIC24 or dsPIC30/33) or 32bit PIC to hook up to an IDE hard drive. But what would you do with it? Run Word? Maybe Open Office and do a little browsing with FireFox. Not any time soon.

Have you looked at the datasheets and product list at www.microchip.com??

That would be a good place to start to see what kind of hardware you're dealing with.

Cheers,

-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D

[aashasurendran]

What I'm trying to do here is, open a file using fopen, read in some values into a variable, perform an algorithm on the numbers and save the new values into a new file. By file, I mean files in the C programming language. I'm trying to do this on the embedded C on the pic. Is file handling possible through the embedded C on the pic?

[bkamen]

Well, I think I can best explain it this way.

First, You'd have to build yourself a PCB where the PIC can plug into an IDE or SATA or maybe SD/CF drive.

Then you'd have to write or buy drivers to handle using FAT. Make sure you get a PIC with lots of memory so you can support FAT32. Keep in mind you'd be limited to opening very few files at any one time.

If you are writing your own drivers, you'll be writing fopen() and all those things.

If you buy someone's, they might have it already.

PIC-C is a compiler that works with the 'C' language to create code that will run on a Microchip embedded microcontroller.

Have you visited their website yet?

I think you want a Windows/Apple/Linux PC for what your needs describe.

-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D

[Wayne_]

bkamen has very good points but I have to ask.
Do you already have some hardware that allows a PIC to connect to a (IDE/SCSI/SATA) hard drive ?
If so what is it and what PIC is it using ?

if you plan on designing this yourself then have a look to see if YOU can actually design and make some hardware to do this. I expect you wouldn't be able to unless you are a very good hardware engineer.

[bkamen]

[dbotkin]

I don't see where he mentioned the drive interface. I think I've seen a PIC project that used IDE drives -- but it's been a while. A Google search turns up a number of PIC/IDE/FAT projects. At this point, though, USB is my personal choice.

Assuming you have suitable hardware, you can at least open, read, write and close text files on a USB FLASH drive pretty easily. Maybe not fopen() easy, but not terribly difficult. I don't have a FAT formatted partition on a USB attached hard drive (only Linux and NTFS), but I expect you use a USB external hard drive as well. In my case I'm using a Vinculum USB host controller chip. It took me some extra work because of all the other stuff I'm doing, but I'm reading & writing text files with no problem. My product will save all of its configuration and the contents of its attached 24LC65 EEPROM, load saved parameter sets, and even bootload its own firmware. It's pretty slick. The downside is, you get the intense pleasure of dealing with a fine-pitch 48 lead LQFP.

Of course, like I said -- this assumes you have the right hardware. And you're not going to figure out the source code with a C textbook and no PIC experience, either. On the bright side, CCS sells a USB dev kit with some nice examples and some USB host mode source to make it a little easier.

[FvM]