Master Boot Record Sd Card

1. Linux Sd Card Boot
2. Master Boot Record Sd Card
3. Windows Boot Sd Card
4. Sd Card Boot Partition
5. Master Boot Record Sd Card Reader

Are you limited by 128 bytes of EEPROM on your MCU or even the few kilobytes of flash in your project? Instead of just downloading a library like Petit FAT File System Module and following blindly a tutorial on how to customize it to your microcontroller and SD card, would you like to really understand what you are doing, and maybe learn a bit about filesystems and SPI in the process?

In this first part of my FAT and SD tutorial, we'll take a SD card image, and create a simple C program to interpret its contents. For this part, you don't need any hardware at all, just a computer with gcc (GNU C Compiler) or any other ANSI C compatible compiler installed.

Getting ready: Hex editor and disk image

Linux Sd Card Boot

To make the coding easier, I recommend a good hex editor. The one I'm using is the free and excellent HxD by Maël Hörz. You can also use it to create a 1:1 disk image from a physical SD card. To have a filesystem to read, I purchased a 1 GB micro-SD card with SD adapter for 5€, plugged it into my computer and formatted it as FAT16 (over 2 GB cards will likely get formatted as FAT32), and copied Hamlet from Project Gutenberg and some other dummy test files to it (also created a subdirectory with a few text files in it):

You can use that label to reference your SD card from now on. I'm going to use disk2 for my example commands, but make sure you use your actual identifier. For a board like the Raspberry Pi, you'll want FAT32 with MBR (Master Boot Record). The Master Boot Record is also a 512 byte sector. This sector contains a partition table with four entries starting at offset 446 (hex. 0x1be is within boot sector. In almost all situations, the SD card is damaged because the file system is damaged or the Master Boot Record is corrupted. File system and Maser Boot Record are like bookkeepers to your SD card. When you access your SD card from any device, the device operating system will access the files through the SD card File system and MBR. The monstrous fifth album from the pioneer of baroque cypher-metal. MASTER BOOT RECORD's highly-awaited 'Direct Memory Access' released on April 20th, 2018.

I then launched HxD in Administrator mode to allow it to open physical disks. Note that you don't open just the one FAT16 partition ('H:'), but the whole removable disk (I circled the icon you need to click first): Download pubg vn pc.

Because the partition data, file system and few test files only occupy only the very beginning the 1 GB disk, I then proceeded to select only the first 1 MB (Edit > Select block… > Offset 0-FFFFF) and copy-pasted that into a new file, which I then saved as test.img in my project folder. If you don't have a smallish SD/micro-SD card at hand, you can just grab the project zip and use my test image.

Note: If you're using Linux or a Mac, you can just use dd if=/dev/sda of=~/test.img bs=1M count=1 to create the image (assuming the kernel selected /dev/sda as the device for your card). You may need to add 'sudo' in the beginning.

Reading the partition data

Now that we have a file image of the SD card (or the beginning of it), we can start poking around. To get going, I first read the FAT on [SD cards] tutorial by Thiadmer Riemersma and Claudio Toffoli of CompuPhase, and I really suggest you to read the 1 page of text under the heading 'The Master Boot Record and the partition table' at this point. In short, we expect the test.img to be roughly laid out like this:

• MBR and partition table
• …maybe some sectors for logical partitions or reserved space…
• Boot sector of a FAT16 partition
• …optionally some reserved sectors…
• 1-2 copies of File Allocation Table (FAT)
• Root directory
• Other directories and data

Update 2013-08-20:: As one of my readers pointed out, some SD/micro-SD cards don't have several partitions and MBR at all, but are formatted like floppy disks of old. Highest rated always sunny episodes. These types of media start straight with a boot sector, described in next section.

Before we go further, you should know that the basic storage block in filesystems is called a sector, and that is simply a 512-byte (256-word) block of data. The MBR and partition table take up one sector. Boot sector will take up one sector. The copies of FAT take some N sectors, and so on. Diskettes and older operating systems used a so-called CHS (cylinder, head, sector) addressing where the sector was the smallest unit, but we don't need to know about cylinders and heads, just the sector will do for now.

From the tutorial I linked above, we learn that the partition table should start at offset 0x1BE (hex numbers are used a lot) and contain four 16-byte partition entries, each laid out in the following manner:

The partition type should be 4 for FAT16 partitions that are less than 32 MiB (MiB = 1024^2 bytes), 6 for over 32 MiB partitions and 14 for FAT16 partitions using LBA addressing. Let's try reading the partition table in C:

Save this as read_mbr.c in the same folder that you saved test.img, and compile with gcc read_mbr.c -o read_mbr.exe and run:

Pretty easy, huh! But reading every field manually gets cumbersome after a while, so we could just define everything in a nice struct. Here's the modified read_mbr2.c:

Note that I printed out only the minimum needed information this time. The __attribute((packed)) is needed so the compiler won't align our data structure fields to 32-bit or 64-bit boundaries (by default, it likes to pad structures with empty areas so the processor can handle the data a bit faster) and make a mess. Also, I'm using a compiler where sizeof(char) is 1, sizeof(short) is 2 and sizeof(long) is 4, adjust your data types if you're using a different system or compiler!

Reading and interpreting the boot sector

Based on the previous output, it is rather evident that the first partition is the one we want to examine further. I now advise you to read the chapter 'FAT and the Boot Sector' from CompuPhase tutorial. Based on the tutorial, the boot sector for a FAT16 file system should nicely fit into this structure:

To make the code a bit more robust, I used a for loop that stops when it finds the first partition with compatible partition type (4, 6 or 14), so the partition entry is in pt[i]. To move inside the image file, we'll first use the fseek() command, then read the boot sector:

I added a few printout commands and saved the result into read_boot.c – you should understand it easily when comparing with read_mbr2.c. The results of a test run can be seen on the right.

Reading the root directory

Before we dive deep into the file allocation table, we'll peek ahead and read the root directory. To do that, we need to skip over any reserved sectors (amount of reserved sectors is bs.reserved_sectors, which includes the boot sector we just read) and all FATs (there are bs.number_of_fats of them, each bs.fat_size_sectors sectors long):

Note that we're using the SEEK_CUR seek mode, which uses the current location as a base. This statement is added after reading the boot sector, which is why we compensate for it by substracting one from bs.reserved_sectors.

Living earth 1 24 download free. For this part, I'm using the Phobos FAT file system tutorial as a reference. It's more detailed on the FAT part than the previous tutorial. 'The Root Directory' chapter contains the information we need to decipher the structure of file entries:

Now that we are in the right position, reading out the entries (there are bs.root_dir_entries of them) is really straightforward:

Note that I'm using a helper function for printing out the file information, as the first character of filename has a special meaning and modification time and date fields are bit-packed. See the source file for details: It's nothing difficult, and if in doubt, you can refer to the clear explanations given for those fields in Phobos' tutorial. I saved everything in read_root.c, compiled and ran it to see if it worked:

Amazing. If you compare this information with the screen capture found in the beginning of this tutorial, we can safely conclude that we are doing at least as good a job as Windows Explorer!

A peek into the future

Sign into icloud apple watch. Now that we have read the root directory, we are basically in the beginning of data area of the file system. Let's try to find the first sector of README.TXT using our hex editor. Before we do that, we need to know that in FAT, the data area is divided into file allocation units called 'clusters', where each cluster is bs.sectors_per_cluster Fnaf ar apk. sectors long. This is because FAT uses 16-bit numbering for clusters and if each cluster was just 512 bytes long, only 32 megabytes of data could be addressed - not quite enough for a 1 GB memory card!

Master Boot Record Sd Card

From read_root.exe output we can see that data area starts at 0x50200 and README.TXT is stored in cluster 0xE (14). Clusters are numbered from 2 onwards (the reason for which we'll learn later), so to reach it, we need to skip 12 clusters (14-2) forward. Based on the output of read_boot.exe, we see that there are 32 sectors per cluster and sector size is 512 (this is 16 kiB, not coincidentally the same value I set as allocation unit size when formatting the SD card), so this is exactly 1232512 bytes or 0x30000 in hex. Firing up my hex editor, I opened the test.img and used the 'Go to' (Ctrl-G) method to locate address 0x80200 (0x50200 + 0x30000):

How cool is that? If you only need to read a maximum of 16 kilobytes, this is all the code you will need to conquer the FAT16 file system. In the next part of this tutorial, I'll show how to navigate the FAT to read files of any size, and maybe expand to writing files or the differences of FAT32. The parts after that will show how to interface with the SD card using a microcontroller, and adapt the code used here for the limited memory of 8-bit AVR chips. So stay tuned, and if you haven't subscribed to the feed already, do it now!

Remark on progressive coding

In this tutorial, I've used the same method of 'building upon the previous iteration' I use myself when tackling larger projects: I start with something really simple, and only once I get that working, I proceed to refine the code for the next step. This way, the amount of information one needs to absorb stays smaller, and you can find problems easier. If you haven't adopted this way of developing already, I warmly recommend it!

The same method can also be applied to any electronics project: Instead of building a IR-controlled egg cooker in one go, start by trying to control the cooker with a manual switch on a breadboard. Then build a version which uses a microcontroller to toggle the switch. Then build the IR-receiver, possibly on a separate breadboard. Only once you've mastered each subject individually, should you combine everything together. That way you'll waste less eggs!

This page is for preparing your SD card for your Nintendo DSi. In the process, we'll format the SD card to a format suitable for the Nintendo DSi and check the card for errors.

Make sure to backup your SD card contents BEFORE following this. Your SD card will be WIPED in the process.

Windows

Section I - Formatting your SD card

1. Download the latest version of GUIFormat
   • Click on the picture on the website to download the app
2. Run GUIFormat with Administrator permissions
3. Select your drive letter
4. Set your Allocation size unit it to 32768
   • If this is too large for your SD, set it to the highest one that works
5. Make sure the Quick Format check box is checked
6. Start the format process

Section II - Checking for errors

1. Go to the properties window of your SD card
   • Windows Explorer -> This PC -> Right click your SD card -> Properties
2. In the tools tab, Select Check Now
3. Check both Automatically fix file system errors and Scan for and attempt recovery of bad sectors
4. Start the checking process

This will scan the SD card and correct any errors it finds

Section III - Checking SD card read/write

1. Download and extract the h2testw archive anywhere on your computer.
   • It can also be extracted on an external device as long as that external device isn't your SD card
2. With your SD card inserted into your computer, run h2testw.exe
3. Select which language you'd like to see h2testw in
4. Set your SD card's drive letter as your target
5. Ensure all available space is selected
6. Click Write + Verify
   • Wait until the process is completed

If the test shows the result Test finished without errors, your SD card is good and you can delete all .h2w files on your SD card

If the test shows any other results, your SD card may be corrupted or damaged and you may have to replace it!

Linux

Section I - Determining which slot your SD card is in

1. Make sure your SD card is not inserted into your Linux machine
2. Launch the Linux Terminal
3. Type watch 'lsblk'
4. Insert your SD card into your Linux machine
5. Observe the output. It should match something like this:
6. Take note of the device mount point. In our example above, it was mmcblk0
   • If RO is set to 1, make sure the lock switch is not slid down
7. Hit CTRL + C to exit the menu

Section II - Formatting the card

1. Type in sudo cfdisk /dev/(device mount point from above)
2. On each partition, hit Delete
3. Create a new Primary partition that covers the size of your entire SD card
   • This will create a new partition with the linux filetype
4. Select type and take a look at the menu
5. Find W95 FAT32 and take note of the code on the left side of that text
6. Press any key, then enter the code you took note of in the previous step
7. Hit enter, then hit Quit

Section III - Using F3

Amazing. If you compare this information with the screen capture found in the beginning of this tutorial, we can safely conclude that we are doing at least as good a job as Windows Explorer!

A peek into the future

Sign into icloud apple watch. Now that we have read the root directory, we are basically in the beginning of data area of the file system. Let's try to find the first sector of README.TXT using our hex editor. Before we do that, we need to know that in FAT, the data area is divided into file allocation units called 'clusters', where each cluster is bs.sectors_per_cluster Fnaf ar apk. sectors long. This is because FAT uses 16-bit numbering for clusters and if each cluster was just 512 bytes long, only 32 megabytes of data could be addressed - not quite enough for a 1 GB memory card!

Master Boot Record Sd Card

From read_root.exe output we can see that data area starts at 0x50200 and README.TXT is stored in cluster 0xE (14). Clusters are numbered from 2 onwards (the reason for which we'll learn later), so to reach it, we need to skip 12 clusters (14-2) forward. Based on the output of read_boot.exe, we see that there are 32 sectors per cluster and sector size is 512 (this is 16 kiB, not coincidentally the same value I set as allocation unit size when formatting the SD card), so this is exactly 1232512 bytes or 0x30000 in hex. Firing up my hex editor, I opened the test.img and used the 'Go to' (Ctrl-G) method to locate address 0x80200 (0x50200 + 0x30000):

How cool is that? If you only need to read a maximum of 16 kilobytes, this is all the code you will need to conquer the FAT16 file system. In the next part of this tutorial, I'll show how to navigate the FAT to read files of any size, and maybe expand to writing files or the differences of FAT32. The parts after that will show how to interface with the SD card using a microcontroller, and adapt the code used here for the limited memory of 8-bit AVR chips. So stay tuned, and if you haven't subscribed to the feed already, do it now!

Remark on progressive coding

In this tutorial, I've used the same method of 'building upon the previous iteration' I use myself when tackling larger projects: I start with something really simple, and only once I get that working, I proceed to refine the code for the next step. This way, the amount of information one needs to absorb stays smaller, and you can find problems easier. If you haven't adopted this way of developing already, I warmly recommend it!

The same method can also be applied to any electronics project: Instead of building a IR-controlled egg cooker in one go, start by trying to control the cooker with a manual switch on a breadboard. Then build a version which uses a microcontroller to toggle the switch. Then build the IR-receiver, possibly on a separate breadboard. Only once you've mastered each subject individually, should you combine everything together. That way you'll waste less eggs!

This page is for preparing your SD card for your Nintendo DSi. In the process, we'll format the SD card to a format suitable for the Nintendo DSi and check the card for errors.

Make sure to backup your SD card contents BEFORE following this. Your SD card will be WIPED in the process.

Windows

Section I - Formatting your SD card

1. Download the latest version of GUIFormat
   • Click on the picture on the website to download the app
2. Run GUIFormat with Administrator permissions
3. Select your drive letter
4. Set your Allocation size unit it to 32768
   • If this is too large for your SD, set it to the highest one that works
5. Make sure the Quick Format check box is checked
6. Start the format process

Section II - Checking for errors

1. Go to the properties window of your SD card
   • Windows Explorer -> This PC -> Right click your SD card -> Properties
2. In the tools tab, Select Check Now
3. Check both Automatically fix file system errors and Scan for and attempt recovery of bad sectors
4. Start the checking process

This will scan the SD card and correct any errors it finds

Section III - Checking SD card read/write

1. Download and extract the h2testw archive anywhere on your computer.
   • It can also be extracted on an external device as long as that external device isn't your SD card
2. With your SD card inserted into your computer, run h2testw.exe
3. Select which language you'd like to see h2testw in
4. Set your SD card's drive letter as your target
5. Ensure all available space is selected
6. Click Write + Verify
   • Wait until the process is completed

If the test shows the result Test finished without errors, your SD card is good and you can delete all .h2w files on your SD card

If the test shows any other results, your SD card may be corrupted or damaged and you may have to replace it!

Linux

Section I - Determining which slot your SD card is in

1. Make sure your SD card is not inserted into your Linux machine
2. Launch the Linux Terminal
3. Type watch 'lsblk'
4. Insert your SD card into your Linux machine
5. Observe the output. It should match something like this:
6. Take note of the device mount point. In our example above, it was mmcblk0
   • If RO is set to 1, make sure the lock switch is not slid down
7. Hit CTRL + C to exit the menu

Section II - Formatting the card

1. Type in sudo cfdisk /dev/(device mount point from above)
2. On each partition, hit Delete
3. Create a new Primary partition that covers the size of your entire SD card
   • This will create a new partition with the linux filetype
4. Select type and take a look at the menu
5. Find W95 FAT32 and take note of the code on the left side of that text
6. Press any key, then enter the code you took note of in the previous step
7. Hit enter, then hit Quit

Section III - Using F3

1. Download and extract the F3 archive anywhere on your computer.
2. Launch the terminal in the F3 directory
3. Run make to compile F3
4. With your SD card inserted and mounted, run ./f3write
   • Wait until the process is complete. See below for an example output:
5. Run ./f3read
   • Wait until the process is complete. See below for an example output:

If the test shows the result Data LOST: 0.00 Byte (0 sectors) your SD card is good and you can delete all .h2w files on your SD card

If the test shows any other results, your SD card may be corrupted or damaged and you may have to replace it!

macOS

Section I - Formatting your SD card

OS X El Capitan (10.11) and later

1. Launch the Disk Utility application
2. Select Show All Devices in the top-left View panel
3. Select your SD card from the sidebar
   • Make sure you choose the correct device, otherwise you might accidentally erase the wrong drive!
4. Click Erase at the top
5. Ensure that Format is set to MS-DOS (FAT)
6. Ensure that Scheme is set to Master Boot Record
   • If Scheme does not appear, click Cancel and make sure to choose the device instead of a volume
7. Click Erase, then click Close

OS X Yosemite (10.10) and earlier

1. Launch the Disk Utility application
2. Select your SD card from the sidebar
   • Make sure you choose the correct device, otherwise you might accidentally erase the wrong drive!
3. Click Partition at the top
   • If Partition does not appear, make sure to choose the device instead of a volume
4. Ensure that Partition Layout is set to 1 Partition
5. Ensure that Format is set to MS-DOS (FAT)
6. From the Options button (below the partition table), select Master Boot Record.
7. Click OK -> Apply -> Partition

Windows Boot Sd Card

Section II - Using F3

1. Open Terminal
2. Install F3 from brew by running brew install f3
   • If you don't have brew, install it with the instructions on brew.sh
3. With your SD card inserted and mounted, run f3write
   • Wait until the process is complete. See below for an example output:
4. Run f3read
   • Wait until the process is complete. See below for an example output:

If the test shows the result Data LOST: 0.00 Byte (0 sectors) your SD card is good and you can delete all .h2w files on your SD card

Sd Card Boot Partition

If the test shows any other results, your SD card may be corrupted or damaged and you may have to replace it!

Master Boot Record Sd Card Reader

You can now restore the contents of your SD card and continue.