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Flashing an open source U-Boot bootloader

What benefits does this open source bootloader have?

  1. You can use H264 FullHD streaming (1920x1080)(on 128MB devices only)
  2. You can boot your own kernel/rootfs from MicroSD
  3. You can change your kernel boot-parameters (uEnv.txt)
  4. You can flash your NAND using this bootloader
  5. It should work on most T20 based devices.
  6. The parameters could be changed through fw_printenv
  7. It is completely open source

What are the disadvantages?

If you flash the wrong u-boot, you can brick your device. I am not taking any responsibility for that!

Requirements:

  1. Determine how much RAM your device has by running following command via SSH:
cat /proc/cmdline

You should get an output like this:

console=ttyS1,115200n8 mem=104M@0x0 ispmem=8M@0x6800000 rmem=16M@0x7000000 init=/linuxrc root=/dev/mmcblk0p2 rootwait rootfstype=ext4 rw mtdparts=jz_sfc:256k(boot),2048k(kernel),3392k(root),640k(driver),4736k(appfs),2048k(backupk),640k(backupd),2048k(backupa),256k(config),256k(para),-(flag)

Sum up the values from each "mem"-section:

mem + ispmem +rmem = 104M + 8M +16M = 128M

i.e. you have a device with 128 Mb RAM.

Flashing the U-Boot bootloader:

  1. Login via SSH
  2. Get the correct bootloader for your device and RAM size.
  3. Put the bootloader file in the root of your microsd card. It will get mounted to /system/sdcard on your camera.
  4. Verify the MD5 hash of the file!! Do not skip this step or you may brick your camera!
  5. Run the following commands
flash_eraseall /dev/mtd0
dd if=/system/sdcard/NAME_OF_YOUR_BOOTLOADER_FILE.bin of=/dev/mtd0

For example, if you're flashing dafang_128mb_v2.bin, your command should look like this:

dd if=/system/sdcard/dafang_128mb_v2.bin of=/dev/mtd0

Don't do anything stupid inbetween. If you crash your camera, you end up without a working bootloader.

Verify that the U-Boot-Loader works correctly

  1. Rename the uEnv.bootfromnand.txt in your minisd card root to uEnv.txt
  2. Reboot your camera

The bootloader is configured to enable the blue led if it has found a valid uEnv.txt during boot up. Take a look at your LED when it first turns on.

If the led turns yellow -> The default configuration is used.

If the led turns blue -> The custom configuration from uEnv.txt is used.

If the led is not turning blue despite having an uEnv.txt on your microsd - try to format the sdcard as FAT16 and try again.

Enable FullHD (on 128 Mb devices only):

Open the uEnv.txt file

vi /system/sdcard/uEnv.txt

and change the "boot-line" from:

mem=104M@0x0 ispmem=8M@0x6800000 rmem=16M@0x7000000

to:

mem=87M@0x0 ispmem=9M@0x5700000 rmem=32M@0x6000000

Reboot and check if the bootline has been applied properly using the following command:

cat /proc/cmdline

My camera doesn't boot/I have failed to flash the bootloader. What can I do now?

You will need to desolder your bootrom, reflash it and solder it back.