Arduino TFT 1.77 backlight with due

Other Hardware Displays
1

Hi,
I'm a programmer with no experience with electronics and I'm working on my first Arduino project,so any help is appreciated.
I'm using Arduino TFT 1.77 (https://www.arduino.cc/en/Main/GTFT) with due board (with no shield).
I use the TFT library to display a logo from an SD for a few seconds and then I prompt the user to enter some input (I use white characters on black background).
All works fine but I would like the text to be as readable as possible in sunlight, should the backlight be always on?
Currntly my lcd BL pin is not connected, if I connect it to the due power (3.3v) I won't get the full backlight? should I use a resistor? which resistor will give the best results for 3.3v and 5v?
I saw that the backlight is dimmable by pwm, if i want to use this option should I just connect the BL pin to one of my due pwm pins? I know the due default pwm frequency is 1khz, is it ok or should I change it? Is there an option to control the BL with the TFT library?

Thanks
Orit

2

Connect the BL line to +5V and the backling will be fully off.
Leaving it unconnected or at 0V will give full backlight brightness, you cannot increase the brightness unless you hack the board and increase the LED current. Increasing the LED current signficantly may damage the LEDs.
Connecting BL to 3.3V may not fully turn off the backlight.
A PWM on BL will give variable brightness, 1KHz will be fine.

These displays give quite poor readability in sunlight as the backlight is not very bright compared to the glare frome the sun. You will need to keep the display shaded as much as possible to see it clearly.