Post by thread:[PIC]: Flash Cards

Hi all, I am going to use a 16F877 to interface to a Flash Card for a vehicle data aquisition system. All I need to do is store the data as a single stream to the memory array and not worry about FAT tables etc. I believe this is possible. Has anyone used the USB Flash Card readers? I am concerned that they expect the cards to be formatted and may not be able to read the data which has essentially been written in random by the PIC. -- Best regards Tony mICros http://www.bubblesoftonline.com spam_OUTsalesTakeThisOuTbubblesoftonline.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Tony Nixon <.....PICLISTKILLspam@spam@mitvma.mit.edu> wrote: > Has anyone used the USB Flash Card readers? I am concerned that > they expect the cards to be formatted and may not be able to read > the data which has essentially been written in random by the PIC. Tony: USB Flashcard readers depend almost universally on a Mass Storage Class Driver running on the host (PC) side; that driver is included in recent versions of most popular operating systems. The driver makes the flashcard reader appear to the PC to be just another mass-storage device like a hard drive; therefore, the PC will expect it to be formatted if you use a commercial reader. If you make your own USB flashcard reader and write your own PC-side driver, of course, you can write to the flashcard any way you like. -Andy === Andrew Warren -- aiwKILLspamcypress.com === Principal Design Engineer === Cypress Semiconductor Corporation === === Opinions expressed above do not === necessarily represent those of === Cypress Semiconductor Corporation -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Hi, Actually, this is more of an "operating system" level, not really USB driver. The USB driver just makes it appear like an ordinary hard disk to the OS, then the application can use the standard OS calls for dealing with hard disks. I've done a flash card based MP3 player. In the end I used FAT16 as the file system, but you can read the raw sectors on the disk. The problem is that the OS will probably ask if you want to format the disk every time you insert it unless you can disable that some how.. Under windows NT/2000/XP you can open a drive for direct access to the sectors. But you do have to have administrator privilege to do it. You use CreateFile() to open the "hard disk" device directly using the name \\.\PHYSICALDRIVEx Where the x is a number. The first drive is 0, then 1, 2 etc.. If you do have a drive letter for the disk, you can also open it as "\\.\C:" or what ever it is. You can also use the handle from CreateFile to get device geometry etc using DeviceIoControl() Here is some code I've used to raw read a drive. I did this with a flash card USB reader.. You just need to keep reading the disk or do a SetFilePointerEx() to set the location to read. Note that you will probably need to align this on sectors. Most are 512 bytes, but you can check this using DeviceIoControl(). char Buf[512]; DWORD dwRead; HANDLE hDrive; HRESULT hr; //TCHAR tszPath[] = _T("\\\\.\\D:"); // alternative name TCHAR tszPath[] = _T("\\\\.\\PHYSICALDRIVE1"); // second hard disk. // attempt to open the drive hDrive = CreateFile( tszPath, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, 0, NULL ); // Make sure it succeeded if( NULL != hDrive ) { // Read the first sector hr = ReadFile( hDrive, Buf, 512, &dwRead, NULL ); // Make sure the ReadFile was successful if( SUCCEEDED(hr) ) { // Buf now contains the data from the first sector. // ... do what ever. } // close the handle when your done CloseHandle( hDrive ); } Hope this helps. Cheers, Ash. --- Ashley Roll Digital Nemesis Pty Ltd http://www.digitalnemesis.com Mobile: +61 (0)417 705 718 > {Original Message removed}

I've just had a quick look at Atmels DataFlash cards. 100 times simpler to interface to and 8Meg is fine for what I need. Small too 32 x 24mm and connectors are available from Farnell. -- Best regards Tony mICros http://www.bubblesoftonline.com .....salesKILLspam.....bubblesoftonline.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

On Fri, Feb 28, 2003 at 09:38:03AM +1100, Tony Nixon wrote: > Hi all, > > I am going to use a 16F877 to interface to a Flash Card for a vehicle > data aquisition system. All I need to do is store the data as a single > stream to the memory array and not worry about FAT tables etc. I believe > this is possible. > > Has anyone used the USB Flash Card readers? I am concerned that they > expect the cards to be formatted and may not be able to read the data > which has essentially been written in random by the PIC. Tony, It'll probably be more of a headache than it's worth. FAT isn't really all the complicated and it'll avoid all the application and OS issues on the PC side. Why not preformat the card with a single partition, FAT16, with a single root directory with a single file that takes all of the card's space and feed it to the PIC. Then you only have to look at one or two fixed spots on the disk for the 1st data block. Then write away. It's just that the container is so useful that it may be worth keeping even though the application doesn't really require it. BAJ -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

On Fri, 28 Feb 2003, Tony Nixon wrote: *>Hi all, *> *>I am going to use a 16F877 to interface to a Flash Card for a vehicle *>data aquisition system. All I need to do is store the data as a single *>stream to the memory array and not worry about FAT tables etc. I believe *>this is possible. *> *>Has anyone used the USB Flash Card readers? I am concerned that they *>expect the cards to be formatted and may not be able to read the data *>which has essentially been written in random by the PIC. Any card reader expects the card to be 'formatted' but access is at (fake) sector level and the real responsability for translating data on the card to files and directories is with the OS. So I do not think that the card reader cares about the format. It does not care for CF and MMC. Peter -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.