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Reprogram MAC address

deanfourie

Jan 30, 2018
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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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kellys_eye

Jun 25, 2010
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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.
 

deanfourie

Jan 30, 2018
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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 30, 2018
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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
 

Nanren888

Nov 8, 2015
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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.
 

deanfourie

Jan 30, 2018
6
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Jan 30, 2018
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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.

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

Jan 30, 2018
6
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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
 
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