Unbricking

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Introduction

This procedure will take you through the restoration of your radio using a simple JTAG cable, with software we have provided.

Prerequisites

In order to recover a bricked radio, you will need:

  • JTAG cable
  • Software for flashing over JTAG
  • An image to flash to the radio
  • A lot of patience

JTAG Cables

'Wiggler' compatible cables are a popular low-cost cable, and well supported by the free jtag tools. Plans to make your own are widely available, and prebuilt ones can be found cheaply on ebay and similar sites. A "universal" wiggler will come with bare wires which can be soldered to the jtag test points on the barracuda board.

Wiggler Schematic

Jtag-soldering.jpg

JTAG Flashing Software

The application sjf2410, along with the error correction code from the linux kernel have been modified to produce a bespoke utility for the baracuda module's NAND flash. It uses the wiggler cable in the parallel port.

This version of sharpflash supports reading and writing of the NAND flash using the wiggler parallel port interface.

Reading Flash Images

You can make a back-up of your flash via JTAG using the following format commands:

sharpflash -r kernel-mtd1.bin 004000 0fc000

Will extract the contents of the kernel partition into 'kernel-mtd1.bin', which is a nanddump format file, skipping any bad sectors as it goes. Have a look at Reciva NAND Flash for the background on the flash structure.


Sharpfin Flash Programmer - http://www.sharpfin.zevv.nl/
.
Found S3C2410 processor on JTAG Cable
Found K9F2808UOC on processor
Reading NAND Flash:
 destination   = kernel-mtd1.bin
 start addr    = 0x4000
 length        = 0xFC000
.
Address  Progress                          Remaining
-------  --------------------------------  ---------
0000000  rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr    9h 12m
0004000  rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr    9h 11m
0008000  rrrrrr

Getting Bad Block Information

This is not needed for programming, however it is recommended that you keep a record of the bad blocks marked by the manufacturer as bad, because this information is stored in re-programmable memory, and it may be useful to be able to distinguish between manufacturer-defined bad blocks, and user-defined bad blocks.

sharpflash -b

The program will output several lines, with each '.' representing a 16K block which is marked as good, and a 'b' for each block which is marked bad.


Sharpfin Flash Programmer - http://www.sharpfin.zevv.nl/
.
Found S3C2410 processor on JTAG Cable
Found K9F2808UOC on processor
Checking NAND Blocks
 0000000: ................................................................
 0100000: bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb...............

Writing Flash Images

This process takes a long time to run - roughly 80 seconds per 16KBytes, so a full 16Mb flash will take about 24 hours.

sharpflash -w boot-mtd.bin 000000 04000

Will write the boot sector from the file boot-mtd.bin, and will produce an output similar to this:

Sharpfin Flash Programmer - http://www.sharpfin.zevv.nl/
.
Found S3C2410 processor on JTAG Cable
Found K9F2808UOC on processor
Writing NAND Flash:
 source      = boot-mtd.bin
 start addr  = 0x0
 length      = 0x04000
.
Address  Progress                          Remaining
-------  --------------------------------  ---------
0000000  wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww    0h 01m

File Formats

Backup images (see Making a backup) can be generated / obtained in several formats, as described below:

nanddump images

nanddump images consist of blocks of 512 bytes of data, and 16 bytes of extra data throughout the file. The extra data must be removed in order for the file to be written back to the flash.

Reciva upgrade images

Reciva upgrade images seem to be a complete image of the boot, kernel and root partitions, however, if this is written back to the flash using sharpflash, the resulting radio still does not boot.

JTAG sharpflash images

JTAG sharpflash images contain raw contiguous data, which skips over any bad blocks identified in the area requested. Two additional files are generated with each image capture: rawdata.bin and rawdata.err, which contain the raw disk data, including bad blocks (in 512 byte chunks), and the extra data, including the error correction data (in 16 byte blocks) respectively.

Interesting Information / Links