The dfRobot backlight circuit was attempting to provide a circuit that allowed backlight control
but turned it on by default. This can be important when using the supplied LiquidCrystal
library which has no backlight control, since the reverse style LCDs (white on blue etc...)
would look "dead" until you turn the backlight on.
I'm sure many novice Arduino users would stumble on this.
While it does turn on the backlight by default, which allows reverse style LCDs to
be visible using the IDE supplied LiquidCrystal hd44780 library,
and allow the backlight to be turned off by setting D10 to LOW,
it shorts the AVR pin when the user later attempts to turn on the backlight back on by setting D10 to HIGH
or when PWM is used.
Before I modified the shield, when D10 was HIGH, I measured the current on the AVR pin at over 100ma!
I sent notes directly to both dfRobot and emartee on 2012-03-14 and so far no response.
--- bill
Update:
I notified RobotShop this morning of the flaw and they responded in less than 45 minutes
that they will be contacting the manufacturer about the issue.
We thank you for pointing this issue out.
We were not aware of this problem and will contact the manufacturer in order to work out a solution.
We will also add a note on the current product in order to prevent people from burning their boards.
That is great customer service & technical support.
--- bill