LED blinking, new audio format proposal - Firmware Dumping - CHDK Forum
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LED blinking, new audio format proposal

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Offline RaduP

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LED blinking, new audio format proposal
« on: 16 / September / 2009, 16:59:36 »
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Well, since the universal dumper doesn't work on some of the new cameras, it might be a good idea to start working at some new tools to extract the firmware.
The blinking method with the soundcard method is not very usefull as it is now, because there is too much noise, and it requires complicated synchronization and timing.

So I was thinking to change the way the blinking is done: Instead of sending 0 as low and 1 as high, how about we do it in a way similar to how the old ZX spectrum computers did it. That is, long pulse 0, short pulse 1, no pulse is the break between two bits.

This way, there are no timing issues, and the software to decode that is pretty easy, you just analyze the file and see how long the pulses are (statistically), then you can tell which is 1 which is 0 even if the bit rate is different.
Of course, this method is slower than just encoding 1 as high 0 as low, but it should be very resilient to noise.
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Offline fe50

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Re: LED blinking, new audio format proposal
« Reply #1 on: 16 / September / 2009, 17:47:47 »
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Offline RaduP

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Re: LED blinking, new audio format proposal
« Reply #2 on: 16 / September / 2009, 21:42:15 »
WOW, I FINALLY managed to get data with that loader, following the instructions. I needed to use a phototransistor, rather than the photodiode.
Also, this is very important, from the readme: "All checkings should be done after 'load.exe' program is started (it sets up RTS and DTR signals)."
I was trying realterm, and that doesn't do it, so I was never getting a good signal :)

I didn't dump the firmware yet, just managed to send 0xaa as a test, but that's very promissing :)
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