Reprogram MAC address

Discussion in 'Microcontrollers, Programming and IoT' started by deanfourie, Jan 30, 2018.

  1. deanfourie

    deanfourie

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    Hey Guys, im trying to reprogram the MAC address on a TCP/IP interface board.

    Im fairly good with RS232 and RS485 communications, but am still learning a lot such as SDI and the various other serial protocols.

    I am tring to reprogram the MAC on the device pictured. My question is, what protocol would I use to connect? RS232? And would I need to find a pinout for this to be achievable?

    On the small pins appears to be a SDI connection. Would I need to use this to connect and would a standard USBTTL work?

    Thanks in advance.
     

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    deanfourie, Jan 30, 2018
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  2. deanfourie

    kellys_eye

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    Is it programmable? Not written to ROM-only?
     
    kellys_eye, Jan 30, 2018
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  3. deanfourie

    deanfourie

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    Yes I am told the mac address can be reprogrammed.
     
    deanfourie, Jan 30, 2018
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  4. deanfourie

    kellys_eye

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    The protocol would depend on the interface established on the circuit board. If the microcontroller is pre-programmed then its boot menu will configure for I/O accordingly and you have to use that protocol.

    The datasheet for the device is comprehensive (!) http://pdf1.alldatasheet.com/datasheet-pdf/view/462367/TI1/LM3S6432.html and page 520 onwards describes the MAC part.

    J3 looks to be the programming header - need a closer look at it to see properly.
     
    kellys_eye, Jan 30, 2018
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    Tha fios agaibh likes this.
  5. deanfourie

    deanfourie

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    Thanks that information is helpful. I now know I'm working with JTAG.

    Yes it would appear that J3 is the programming UART. I have attached a picture.

    I have also uploaded a images of the USBasp programmer I have. Will this work for JTAG?

    I guess my next question is, simply how to initiate a connection using the JTAG protocol. Can I use the Auduino software?

    What pins need to be connected and do any pins need reversing ie. TX >> RX RX >> TX.

    Thanks for the help. The purpose of this exercise is simply to reprogram the MAC but more to get to know these serial protocols in a bit more depth.

    Thanks
     

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    deanfourie, Jan 31, 2018
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  6. deanfourie

    kellys_eye

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  7. deanfourie

    deanfourie

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    Ok I have done some research on the JTAG and Boundary Scan protocol. I am just still a little unsure how to actually establish a connection, or what application to use. Can I use Arduino software?

    Then once connected how do I reporgram the MAC? Do I need to flash a file? I am just not sure how the UI looks once connected. Is it like a CLI based setup?

    Thanks
     
    deanfourie, Feb 12, 2018
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  8. deanfourie

    Nanren888

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    Sorry, I might have missed something, but I have to ask.
    You want to assign a new MAC address.
    Why?
    Mostly interest. I know many now let you do this, but how often is that a need.
    .
    For how, sounds like some more reading on JTAG will help.
     
    Nanren888, Feb 12, 2018
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  9. deanfourie

    deanfourie

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    Yes I would like to assign a new MAC address because the previous MAC has been lost and is appearing as all FFs. Ideally not assign a new one, but even just reassign the original MAC.

    However, with the MACs all FF as a broadcast MAC, this is causing issues with ARP and simple layer 2 networking tasks.

    This is a network card, designed for a security access system which allows for TCP/IP connections to the management software, but when trying to get the connection to work over a ubiquiti wireless link, I discovered the issues was ARP not assigning an IP address to the unit as the MAC is all Fs.

    Hope that helps ;)
     
    deanfourie, Feb 13, 2018
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  10. deanfourie

    deanfourie

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    What I am trying to achieve is just use JTAG as a serial connection to establish a connection to the board, and issue the MAC.

    Via serial or VCP, or TTL whatever it be, I would use a serial emulator such as putty, and insert a break on boot to access the boot rom, and from there I could issue the commands required.

    I guess, I am not sure how the JTAG protocol is used as far as, GUI, CLI? or just straight flashing a HEX or image to the device that needs to be created first.

    If you get my flow.

    Cheers
     
    deanfourie, Feb 13, 2018
    #10
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