This technique is sometimes used when reverse engineering. For example, if you can find a way to run code on a device and control an LED on it, it can then be p

This technique is sometimes used when reverse engineering. For example, if you can find a way to run code on a device and control an LED on it, it can then be possible to dump the device's firmware through flashing the LED. This is exactly how the CHDK project[1] managed to obtain firmware dumps[2] of various Canon cameras when they were first being reverse-engineered. I used the same technique myself when I soft-bricked my camera and needed to see the camera's internal log messages to understand where the problem was. I redirected the log out to the LED, recorded them using a photodiode and my PC soundcard input, then reconstructed logfile from the soundwave that was recorded. To my surprise and pleasure, it worked first time and gave some of the clues needed to eventually revive the camera. [1] http://chdk.wikia.com/wiki/CHDK http://chdk.wikia.com/wiki/CHDK [2] http://chdk.wikia.com/wiki/Obtaining_a_firmware_dump http://chdk.wikia.com/wiki/Obtaining_a_firmware_dump