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how to confirm if the fuse is blown on the msp430g2231 and msp430g2232

steven mylrea
Prodigy 210 points
Other Parts Discussed in Thread: MSP-FET, MSP430G2232

Hi,

i have wired my MSP FET according to the 2 wire JTAG schematic i found here:

http://processors.wiki.ti.com/index.php/JTAG_(MSP430)

without the fuse blown i get the communication fine and can program the device. once i click run>advance>make device secure and click ok to blowing the fuse i can not get communication again.

i do not get any message saying fuse was blown. when i try to connect i get 

MSP430: Error connecting to the target: Unknown device

i have also tried with the Lite Fet-pro430 software and using the launchpad i can verify the fuse is ok but not blow the fuse as that is not supported.

when i try to connect with the msp-fet using the lite fet-pro430 software i can not verify the fuse is not blown but using code composer i can communicate so i know it's not blown.

is there a simple check i can do to confirm the fuse is blown?

is previous times of programming i had got a message "could not connect as the fuse is blown" this was solved by relaunching the target configuration.

i was expecting the message to say could not connect because the fuse was blown but instead after i blow the fuse i just get a message: 

MSP430: Error connecting to the target: Unknown device

look forward to the help as always!

sincerely,

Steven

  • 0
    Prodigy 210 points

    i also had a question about how secure it actually is. with probing could someone get the code? obviously not the source but would someone be able to duplicate it? should i use under-fill or is it not necessary?

  • 0 in reply to steven mylrea
    Guru 227245 points

    On 1x, 2x and 4c family, a blown fuse is a physical destruction of part of the JTAG logic. Only the JTAG bypass command will still work. The only other way to retrieve the binary code from the device will be through BSL. For BSL access, you’ll need the BSL password, which is part of the interrupt vector table. So to read the firmware, you’ll need the password, which means you’ll have to know the firmware (or at least the vector table). The only option left is a brute-force attack on the BSL password, which will take a looong time.
    On 5x family MSPs, the fuse is a software fuse and can be “unblown”. Besides the bypass command, the JTAG mailbox commands will still work. However, access to the MSP with blown fuse is again only possible through the password-protected BSL. And here, picking a wrong password will trigger a mass-erase. So on first unsuccessful attempt to ‘hack’, the firmware is gone. If you do a forum search, you might find an old thread where Old Cow Yellow and I are discussing ways to hack into the BSL.

     Your ‘unknown device’ error is a symptom of a malfunctioning JTAG connection. Just what one would expect if the JTAG fuse was blown. Even though a 'cannot communicate' error is more typical.

  • 0 in reply to Jens-Michael Gross
    Prodigy 210 points

    my understanding was that on the msp430g2232 there was no bsl...? is ther a bsl that is accessable?

    should i get a message that says fuse was blown successfully?

    what is the jtag bypass command?

    thanks,

    steven

  • 0 in reply to steven mylrea
    Guru 227245 points

    The smaller G2 series MSPs don’t have a BSL. If there is none, then of course it is not accessible. :)

    Whether you get a message for a successful fuse blow depends on the software.

    The Elprotronic software has a separate ‘check fuse’ funciton.
    But basically, it only checkes whether JTAG access works or not. (and the ‘blow fuse’ button is fool-proof with additonal check box to enable it etc.)

    Teh JTAG bypass command is for chaining JTAG devices. You send a bypass command to the first one in the chain, and it will pass the following command through to the next device.
    However, none of the MSP tools does support bypassing for chaining MSPs.
    I don't know whether it has ever been tried, but it could be possible to chain a totally different JTAG device (the MSP being the first one in the chain) and access it with a different JTAG tool (not the MSP FET) through the same JTAG connector, saving some PCB space.

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