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    N900: JTAG or serial console over USB?

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    arachnist | # 1 | 2009-10-23, 12:32 | Report

    Does the N900 provide a JTAG or a serial console over USB?
    It'd be very helpful for fixing stuff if one screws-up with partitioning the mtd device or uploading the ubifs.
    I would like to avoid pulling to pieces my N900 once it finally arrives, just to get myself a "seatbelt" for "just in case i screw-up".

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    Alex Atkin UK | # 2 | 2009-10-23, 22:19 | Report

    From what iI have read I believe the idea is you will not be messing with the boot loader so it should never be entirely bricked.

    Presumably the boot loader has a recovery mode over USB?

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    arachnist | # 3 | 2009-10-24, 01:37 | Report

    With jtag over usb available, it should be possible to even wipe the device entierly (including the uboot bootloader, which is most probably used) and still recover from it, provided one had kernel and os image.

    I think that this what the flasher uses, though without an actual device (thanks for the delays...) it won't be possible to check.

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    sarahn | # 4 | 2009-10-24, 03:58 | Report

    I guess you might be able to pile a whole bunch of stuff into initramfs. If that works let me know.

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    zimon | # 5 | 2010-11-17, 17:37 | Report

    Has anyone tried to clear mtd2?

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    rambo | # 6 | 2010-11-18, 13:52 | Report

    Doing it over the USB might be kinda hard (it would have to be a feature of the bootloader and I'm not sure JTAG could be done in such way), but do take a look at http://wiki.maemo.org/N900_Hardware_Hacking#Debug_ports

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    fnordianslip | # 7 | 2010-11-18, 14:05 | Report

    The sheevaplug offers these options via built in JTAG and Serial interface hardware conected to its USB Peripheral interface. It's a nice approach, but the N900 doesn't do that.

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    rlinfati | # 8 | 2010-11-18, 14:13 | Report

    https://wiki.maemo.org/Updating_the_.../Cold_Flashing

    Cold flashing (N900)

    If the bootloader is deleted/destroyed with dd, then it is possible to recover it with a cold flash.....

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    zimon | # 9 | 2010-11-19, 15:46 | Report

    Originally Posted by rlinfati View Post
    https://wiki.maemo.org/Updating_the_.../Cold_Flashing

    Cold flashing (N900)

    If the bootloader is deleted/destroyed with dd, then it is possible to recover it with a cold flash.....
    Will that work, if you wipe out all mtd devices to zeros with dd?


    # cat /proc/mtd
    dev: size erasesize name
    mtd0: 00020000 00020000 "bootloader"
    mtd1: 00060000 00020000 "config"
    mtd2: 00040000 00020000 "log"
    mtd3: 00200000 00020000 "kernel"
    mtd4: 00200000 00020000 "initfs"
    mtd5: 0fb40000 00020000 "rootfs"

    I still have this problem. Flashing both rootfs and eMMC with PR1.3 images didn't fix the problem, so something still hides inside the phone which makes it buggy with this one operator's SIM-card.

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    egoshin | # 10 | 2010-11-19, 19:28 | Report

    Originally Posted by zimon View Post
    Will that work, if you wipe out all mtd devices to zeros with dd?


    # cat /proc/mtd
    dev: size erasesize name
    mtd0: 00020000 00020000 "bootloader"
    mtd1: 00060000 00020000 "config"
    mtd2: 00040000 00020000 "log"
    mtd3: 00200000 00020000 "kernel"
    mtd4: 00200000 00020000 "initfs"
    mtd5: 0fb40000 00020000 "rootfs"

    I still have this problem. Flashing both rootfs and eMMC with PR1.3 images didn't fix the problem, so something still hides inside the phone which makes it buggy with this one operator's SIM-card.
    You can't solve that problem with reflashing. It is operators.

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