Backlight auto-adjuste

Hi

My customer use product during the day and the night. The problem is in night the backlight is too hight. It is possible to change with the menu, or with a button to switch in night mode. it's work but is not auto-adjuste.

Three possibility to do an auto-adjust-backlight

1 - add a light sensor (light Garmin GPS)

2 - add a function who calculate the sunrise and sunset with latidude/longitude in input. I have made this fonction it is works great. But if the system loose date or the customer change place (it is possible with our product), it doesn't works. Like that there a number 3

3 - add a GPS module on your module (now a GPS module is very low cost (5$)), like that always on time, you have the real speed, and you can use the auto-adjuste-module

Regards