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Flashing an Open-Source U-Boot

What benefits does this open source bootloader have?

  1. You can use H264 FullHD Streaming (1920x1080)
  2. You can boot your own kernel/rootfs/whatever 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 nearly all T20 based devices.
  6. The parameters could be changed through fw_printenv
  7. It is completely open source - Check the source here: https://github.com/Dafang-Hacks/uboot

What are the disadvantages?

  1. Its not stock - maybe some optimisations to specific devices are missing
  2. There is no ethernet support on the bootloader level. You cannot use TFTP to flash back your NAND(even) However, you can still use a serial interface and/or the microsd slot.
  3. You can brick your device, if you flash the wrong u-boot. I am not taking any responsibility for that!

Requirements:

  1. Find out how much RAM your device have by running following command via SSH:
[root@DafangHacks:~]# cat /proc/cmdline

You will get an output similar to that:

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)

Count together the values from each "mem"-section:

mem = 104M

rmem = 16M

ispmem = 8M

-> Together 128M -> You have a 128Mb Ram Device

Flashing U-Boot:

  1. Login via SSH

  2. Get one of the following Files according to your amount of Ram: https://github.com/Dafang-Hacks/kernel_release/tree/master/uboot

  3. Run

for 64Mb Devices:

flash_eraseall /dev/mtd0
dd if=opensource-T20-V1.3-64MB.bin of=/dev/mtd0

for 128Mb Devices:

flash_eraseall /dev/mtd0
dd if=opensource-T20-V1.3-128MB.bin of=/dev/mtd0

Verifying the U-Boot-Loader

  1. Get a uEnv.bootfromnand.txt file from*__* this repository.
  2. Rename the uEnv.bootfromnand.txt to uEnv.txt
  3. Boot your camera

The bootloader is configured to enable the blue-led if it takes the configuration from the uEnv.txt as soon as it boots up. Take a look at your LED when it first turns on.

If it turns yellow -> The normal configuration is being taken

If it turns blue -> Custom Configuration from uEnv.txt is being taken.

If its not turning blue despite that you have a uEnv.txt on your microsd - try to format it as FAT16 and try again

Turning on FULLHD:

Open up the uEnv.txt file 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

Check if its being applied using the following command:

[root@DafangHacks:~]# cat /proc/cmdline

My camera doesn't boot/I have failed flashing the bootloader - what now?

You will need to desolder your chip, reflash it and solder it back. Here is information about how to do it: https://github.com/Dafang-Hacks/spiflasher