Originally Posted by ProDigit
Their forward voltage is 3V, their backwards voltage could sometimes range in the tens of Volts.
I'm sure that the sub 3,6V is not going to harm them.
Besides if it was voltage oriented, and the kindle had 2 x 3,6V batteries, the '-1' would be only a 1/256th of 7,2V, or 0.03V, which would not harm the leds.
If it is like you say, digital (which you're probably correct), then value '0' could mean always on, or always off (I mean, it is a possibility that the timer set to zero, might actually keep the voltage regulator in it's previous state, which might be 'on').
More than likely it'll be off though...
As was posted earlier in this thread (more than once), I posted the values and their brightness levels back in October. The slider sets a maximum value of 254 and a minimum value of 1, but from a script or command line you can set 255 or 0 (which is completely off).
As mentioned previously, most common LEDs have a MAXIMUM reverse breakdown voltage of 5V. Exceeding that value can destroy them.
The kindles may contain voltage converters, so you cannot safely assume that all voltages in the device are less than the battery voltage. Anyway, it does not make sense to dedicate a DAC (especially a bipolar DAC that would require positive AND negative supply voltages) to controlling the LEDs when it makes no sense to reverse bias them.