[How To] Unpack and Repack for Custom Firmwares for Rockchip RK28xx

This applies to the Archos 7 Home Tablet, Apad iRobot, or any other Rockchip RK2808/RK2808a devices.

Instructions are for use with Windows and Linux together.

First, download the generic RK2808 dev tool:
MydroidDevTool_v1.0CN+Apad_iRobot_0611.zip - apad-irobot - Rockchip SDK Update Flash and Package Tool Chinese (MydroidDevToolv1.0) with Apad iRobot 0611CN - Project Hosting on Google Code

To create Rockchip ROMs, you should start with a stock firmware. If the file is in update.img format, you need to unpack it using AFPTool.exe included with MydroidDevTool, in the folder 'rockdev'.

AFPTool allows you to create and unpack update.img files.

You can unpack images with afptool -unpack update.img folder_to_extract_to

After unpacking the image, you will be presented with update-script, parameter, and a bunch of .img files.

Here's a rundown:

The only file we need to modify are typically system.img, and sometimes boot.img depending on what you are trying to do.
system.img, boot.img, and recovery.img are all cramfs file systems and can be unpacked with cramfs.

In Ubuntu, you need to install the packages:

Code:

sudo apt-get install cramfsprogs fusecram

A shell script I use to unpack system images is the following:

Code:

#!/bin/sh
mkdir system
sudo mount -t cramfs -o loop system.img  system
tar cvzf system.tgz system
sudo umount system
tar xzvf system.tgz

Run the script in a Terminal shell, and the contents will be extracted into system. Alternate you can find out how to run uncramfs.

You can perform the changes you like, and repack it with the following:

Code:

mkcramfs system system.img

boot.img and recovery are tricker because they require a special CRC appended at the end. Luckily, a Japanese Apad iRobot user reverse engineered the CRC (https://sites.google.com/site/naobsd/android-tablet/apad-irobot).

Unpacking is the same procedure as system.img, but when you pack, you need to run:

Code:

mkfs.cramfs -n v1.01 bootfs boot.img

This will generate a compatible boot.img file without a CRC, which still wont boot yet. So to add the CRC, I am still using the old method. You can find out the new method on naobsd's webpage.

Download genrkcrc.c:

Code:

/*-
 * Copyright (c) 2010 FUKAUMI Naoki.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdint.h>
#include <unistd.h>

uint32_t t[256] = {
    0x00000000, 0x04c10db7, 0x09821b6e, 0x0d4316d9,
    0x130436dc, 0x17c53b6b, 0x1a862db2, 0x1e472005,
    0x26086db8, 0x22c9600f, 0x2f8a76d6, 0x2b4b7b61,
    0x350c5b64, 0x31cd56d3, 0x3c8e400a, 0x384f4dbd,
    0x4c10db70, 0x48d1d6c7, 0x4592c01e, 0x4153cda9,
    0x5f14edac, 0x5bd5e01b, 0x5696f6c2, 0x5257fb75,
    0x6a18b6c8, 0x6ed9bb7f, 0x639aada6, 0x675ba011,
    0x791c8014, 0x7ddd8da3, 0x709e9b7a, 0x745f96cd,
    0x9821b6e0, 0x9ce0bb57, 0x91a3ad8e, 0x9562a039,
    0x8b25803c, 0x8fe48d8b, 0x82a79b52, 0x866696e5,
    0xbe29db58, 0xbae8d6ef, 0xb7abc036, 0xb36acd81,
    0xad2ded84, 0xa9ece033, 0xa4aff6ea, 0xa06efb5d,
    0xd4316d90, 0xd0f06027, 0xddb376fe, 0xd9727b49,
    0xc7355b4c, 0xc3f456fb, 0xceb74022, 0xca764d95,
    0xf2390028, 0xf6f80d9f, 0xfbbb1b46, 0xff7a16f1,
    0xe13d36f4, 0xe5fc3b43, 0xe8bf2d9a, 0xec7e202d,
    0x34826077, 0x30436dc0, 0x3d007b19, 0x39c176ae,
    0x278656ab, 0x23475b1c, 0x2e044dc5, 0x2ac54072,
    0x128a0dcf, 0x164b0078, 0x1b0816a1, 0x1fc91b16,
    0x018e3b13, 0x054f36a4, 0x080c207d, 0x0ccd2dca,
    0x7892bb07, 0x7c53b6b0, 0x7110a069, 0x75d1adde,
    0x6b968ddb, 0x6f57806c, 0x621496b5, 0x66d59b02,
    0x5e9ad6bf, 0x5a5bdb08, 0x5718cdd1, 0x53d9c066,
    0x4d9ee063, 0x495fedd4, 0x441cfb0d, 0x40ddf6ba,
    0xaca3d697, 0xa862db20, 0xa521cdf9, 0xa1e0c04e,
    0xbfa7e04b, 0xbb66edfc, 0xb625fb25, 0xb2e4f692,
    0x8aabbb2f, 0x8e6ab698, 0x8329a041, 0x87e8adf6,
    0x99af8df3, 0x9d6e8044, 0x902d969d, 0x94ec9b2a,
    0xe0b30de7, 0xe4720050, 0xe9311689, 0xedf01b3e,
    0xf3b73b3b, 0xf776368c, 0xfa352055, 0xfef42de2,
    0xc6bb605f, 0xc27a6de8, 0xcf397b31, 0xcbf87686,
    0xd5bf5683, 0xd17e5b34, 0xdc3d4ded, 0xd8fc405a,
    0x6904c0ee, 0x6dc5cd59, 0x6086db80, 0x6447d637,
    0x7a00f632, 0x7ec1fb85, 0x7382ed5c, 0x7743e0eb,
    0x4f0cad56, 0x4bcda0e1, 0x468eb638, 0x424fbb8f,
    0x5c089b8a, 0x58c9963d, 0x558a80e4, 0x514b8d53,
    0x25141b9e, 0x21d51629, 0x2c9600f0, 0x28570d47,
    0x36102d42, 0x32d120f5, 0x3f92362c, 0x3b533b9b,
    0x031c7626, 0x07dd7b91, 0x0a9e6d48, 0x0e5f60ff,
    0x101840fa, 0x14d94d4d, 0x199a5b94, 0x1d5b5623,
    0xf125760e, 0xf5e47bb9, 0xf8a76d60, 0xfc6660d7,
    0xe22140d2, 0xe6e04d65, 0xeba35bbc, 0xef62560b,
    0xd72d1bb6, 0xd3ec1601, 0xdeaf00d8, 0xda6e0d6f,
    0xc4292d6a, 0xc0e820dd, 0xcdab3604, 0xc96a3bb3,
    0xbd35ad7e, 0xb9f4a0c9, 0xb4b7b610, 0xb076bba7,
    0xae319ba2, 0xaaf09615, 0xa7b380cc, 0xa3728d7b,
    0x9b3dc0c6, 0x9ffccd71, 0x92bfdba8, 0x967ed61f,
    0x8839f61a, 0x8cf8fbad, 0x81bbed74, 0x857ae0c3,
    0x5d86a099, 0x5947ad2e, 0x5404bbf7, 0x50c5b640,
    0x4e829645, 0x4a439bf2, 0x47008d2b, 0x43c1809c,
    0x7b8ecd21, 0x7f4fc096, 0x720cd64f, 0x76cddbf8,
    0x688afbfd, 0x6c4bf64a, 0x6108e093, 0x65c9ed24,
    0x11967be9, 0x1557765e, 0x18146087, 0x1cd56d30,
    0x02924d35, 0x06534082, 0x0b10565b, 0x0fd15bec,
    0x379e1651, 0x335f1be6, 0x3e1c0d3f, 0x3add0088,
    0x249a208d, 0x205b2d3a, 0x2d183be3, 0x29d93654,
    0xc5a71679, 0xc1661bce, 0xcc250d17, 0xc8e400a0,
    0xd6a320a5, 0xd2622d12, 0xdf213bcb, 0xdbe0367c,
    0xe3af7bc1, 0xe76e7676, 0xea2d60af, 0xeeec6d18,
    0xf0ab4d1d, 0xf46a40aa, 0xf9295673, 0xfde85bc4,
    0x89b7cd09, 0x8d76c0be, 0x8035d667, 0x84f4dbd0,
    0x9ab3fbd5, 0x9e72f662, 0x9331e0bb, 0x97f0ed0c,
    0xafbfa0b1, 0xab7ead06, 0xa63dbbdf, 0xa2fcb668,
    0xbcbb966d, 0xb87a9bda, 0xb5398d03, 0xb1f880b4,
};

int
main(void)
{
    uint32_t i;
    uint8_t c1, c2;

    i = 0;

    while (read(STDIN_FILENO, &c1, 1) == 1) {
        c2 = (i >> 24) & 0xff;
        c2 ^= c1;
        i <<= 8;
        i ^= t[c2];
    }

    c1 = (i >> 0) & 0xff;
    write(STDOUT_FILENO, &c1, 1);
    c1 = (i >> 8) & 0xff;
    write(STDOUT_FILENO, &c1, 1);
    c1 = (i >> 16) & 0xff;
    write(STDOUT_FILENO, &c1, 1);
    c1 = (i >> 24) & 0xff;
    write(STDOUT_FILENO, &c1, 1);

    return 0;
}

Compile it (gcc -o genrkcrc genrkcrc.c) and make genrkcrc executable.

Now put boot.img in the same folder and run:

Code:

./genrkcrc < boot.img | cat boot.img - > bootCRC.img

Your outputted file in bootCRC.img is now a compatible boot image for your Rockchip RK2808/RK2808a device.

To complete this, you need to reboot to Windows and replace the files in the SDK under /rockdev/ with what you have unpacked. Then within /rockdev/Image, replace the .img files you have modified. At this point you may choose to pack the firmware into a new update.img by running mkupdate.bat in /rockdev, or by flashing it directly to your device using the tool RKAndroidTool.exe

FOR RK2818, the only difference is that you should sign system.img as well, and use AFPTool for RK2818 to package the firmware instead of AFPTool for RK2808

i have been reading through all of your tutorials and they are great, you are full of information

Not sure how that's done, but you might try compiling a kernel driver module for Linux kernel 2.6.25 for your particular GPS. But I am not sure what you need to initialize it after you insmod the driver module.

I never bothered adding the crc to system.img. Never realized there was a crc. It was booting just fine so

My initlogo.rle is pretty heavy. It boots fine. The space allocated for boot.img is pretty big actually.

No clue. naobsd figured it out already, but I am not sure where he published his results.

This should work for the RK2818: Forum.ArchosFans.com - View topic - How to create a custom rom for the A7HT Versions 2 (RK2818)?

They put the RK2818 info into their wiki now. It's nice of them: Dump your Home Tablet rom and create a custom rom - Wiki.ArchosFans.com