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TatumAH Offline OP
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Obviously having some problems unlocking the article!


[url=https://www.nytimes.com/2021/03/02/science/locked-letters-unfolding.html?surface=home-discovery-vi-prg&fellback=false&req_id=225570103&algo=identity&variant=no-exp&imp_id=350914233&action=click&module=Science%20%20Technology&pgtype=Homepage]New Technique Reveals Centuries of Secrets in Locked Letters/url]

Quote:
New Technique Reveals Centuries of Secrets in Locked Letters

M.I.T. researchers have devised a virtual-reality technique that lets them read old letters that were mailed not in envelopes but in the writing paper itself after being folded into elaborate enclosures.


In 1587, hours before her beheading, Mary, Queen of Scots, sent a letter to her brother-in-law Henry III, King of France. But she didnt just sign it and send it off. She folded the paper repeatedly, cut out a piece of the page and left it dangling. She used that strand of paper to sew the letter tight with locking stitches.

In an era before sealed envelopes, this technique, now called letterlocking, was as important for deterring snoops as encryption is to your email inbox today. Although this art form faded in the 1830s with the advent of mass-produced envelopes, it has recently attracted renewed attention from scholars. But they have faced a problem: How do you look at the contents of such locked letters without permanently damaging priceless bits of history?



Last edited by TatumAH; 03/02/21 03:47 PM.

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sevil regit
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I suspect that kind of x-ray tomography could be used to reverse engineer silicon chips. They have multiple layers, which makes it near impossible to tell how the buried layers are interconnected. But buried gates would actually be pretty easy to identify with this kind of layered images. In a digital design, typically everything is just transistors interconnected in standard ways. Transistors would be very easy to identify. So would resistors and capacitors.

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TatumAH Offline OP
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I'm in the process of trying to reverse engineer a an electronic control box that sends signals to LEDs embedded in a 1998 guitar fretboard, to help visualize the various scales and chords. It obviously is a serial signal that is programed to light up patterns on a LED 6 wide x 22 fret long matrix. Unfortunately it has an EPROM with a proprietary program written in it that controls the CPU, and naturally no help from the makers, as they want me to buy a new one with the modern bluetooth wireless MIDI, but their new guitar bodies are crap made in china, I would like to be able to program the guitar array the way I want it, as the technology of programmable LED arrays has much improved over the last 20 years!
It is not MIDI, but I would like to have it driving by a MIDI signal. So I in the process of learning and tinkering with the bigger Arduino-like boards, and learning more than I wanted to about the complexity of MIDI communication. I know there are ways of reverse engineering PROMs, but that is so far above my pitiful skill set that its laughable.


There's nothing wrong with thinking
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sevil regit
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The usual way to reverse engineer PROMs of any sort is just to plug them into an EPROM programmer and read them into your computer memory. Then you can save the file and run it through a disassembler for the particular microprocessor. That would give you a non-commented assembler listing. Then you get to figure out the mapping of peripherals it's talking to, the protocols it's using, and what the hell the original authors were doing, etc. If it was originally some language other than assembler, that makes it a bit trickier but not much. Then you can make any changes you like, put that compiled program into a new EPROM, and see if it does what you want. This is hard-core embedded system engineering.

If that fretboard has discrete LEDs and you can get to the wiring, it might be easier to just buy a new one and wire it up to the old LEDs in the original fretboard. LEDs are still the same as they were 20 years ago. No microprocessor ever made has 6 x 22 digital outputs, so they must be sending a digital sequence out to some latches every few milliseconds. That design might have changed, but the wires to the discrete LEDs are just one wire each with a common connection to all of them. That's usually a positive voltage in common, and the latch outputs pull down the LED signal to light it. Each LED will also have a current limiting resistor in series with the latch signal. Even with all the soldering and splicing, it would be easier than the software approach.

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TatumAH Offline OP
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Fortunately all that reverse engineering of PROMS became unnecessary, because to deprogram you have to be a programmer first. It was never going to happen! I was trying to figure out they addressed 6 rows of 22 leds, with multiplexing etc, and all the 50 something wires to leds are accessible, but I have been afraid to experiment with manually lighting them, cause if I blew one embedded in the fretboard, it couldn't be repaired.

I received the rest of the electronics on Friday after, a two week delay by "express mail" from Oregon, that has the original box that patches the guitar to a serial com port. I unmothballed three dell windows XTs that had been "upgraded" to 2000 to find machines that might run the old program guitar OS from 1997, that specifically said it was not XT ready, and it was on virgin still sealed 3.5 inch floppies. It loaded and installed first try. Then i had to review com ports and dig though the bags and boxes of old cables I had been saving for just such an occasion. Most of the time was spent untangling the medusa of cables. Hooked everything up, to the wrong 25 pin female which didnt work. Then found a RS232 to 25 pin cable and hooked everything to the RS232 output, configured the port and bingo everything lit up! Scales, chords, and chord sequencer etc and it even has a translator of MIDI to its proprietary soft and hardware. But I sure learned a lot in the process and will be getting into some of those kool LED products from addafruit and try to learn their circuitpython that doesn't need compiling.
Thanks for the analysis, it kept me going and learning. Gotta keep those neuron regenerating and plastic!
Tat

Here is what some hacker did with the more or less open software, that show that each led is individually addressable. The musical content is completely cooincidental grin

Last edited by TatumAH; 03/09/21 03:07 PM.

There's nothing wrong with thinking
Except that it's lonesome work
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