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Any known issues with reactivgating Display_T35 backlight after a long period of being off?


#1

Hi everyone,

I have a little project that I’ve been working on. The project uses a T35 Display. It’s supposed to run 24x7, and after running the device for a couple of days, it occurred to me that it would be better if I turned off the backlight after a period of inactivity. So, I hooked up an activity timer and turn off the display’s backlight after 30 seconds of inactivity. (Whenever the display is touched, I stop and restart the timer).

Anyway, things seem to work well for an hour or so… but some time after an hour of inactivity, I can’t wake the display back up (turn on the backlight). I left the device hooked up under the debugger last night - thinking there was some sort of unhandled exception causing me grief, but to my surprise there were no exceptions. In fact, the program on the device seemed to be working just fine after hours of inactivity. However, touching the screen wouldn’t force the display back on. Since the little guy was running under the debugger, I set a break point on the touch event handler just to see what was going on. Touching the display showed that the handler got invoked. I even stepped over the line that turned the backlight on. But, the backlight didn’t come on!

Is there something going on that I’m not aware of? Some sort of display disablement? Resetting the device after getting into this state made everything okay again.

Maybe it’s just a bug in my project. I don’t know.

Thanks


#2

I have been working with the backlight without using Gadgeteer and haven’t had any problems.

I just turn it on and off via the GPIO pin. Or dim it using a PWM port.


#3

Thanks!

I went through the debug output again - this time with a finer toothed comb and noticed that there was a spot in my code that was generating an exception. I had a function that was designed to update the display with some values; it turns out that somehow, I was sending null in as a parameter value to this function and the function was trying to copy values out of the parameter into Glide TextBlocks. I don’t know if this is causing the backlight problem, but am wondering if this is somehow goofing the display up. Anyway, I put in a check for null and am hoping it fixes the issue. Won’t be able to test it out again until tonight.