Author Topic: TFT Shield - backlight  (Read 1352 times)

John99041

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TFT Shield - backlight
« on: July 16, 2016, 01:42:23 am »
Hi all,

ive finally found some time to play with some of the bits I ordered during the KS campaign. I've got a project using an Oak and the TFT shield and was wondering if any one had worked out how to control the backlight? Ideally I wanted to control the light level using a PWM pin so that as the room gets darker the light can dim, this would also allow me to turn the backlight off completely at night.

I've had a look and it seems that the lib does not support backlight control and it looks like the backlight pin (LED?) on the panel is connected to Vcc (via the resistor) is this correct?

Thanks

John

saperlot

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Re: TFT Shield - backlight
« Reply #1 on: August 03, 2016, 07:58:41 am »
yes correct, althought you can modify it to get it controlled by a pin by cutting traces and rewiring thought.

Cheers

PeterF

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Re: TFT Shield - backlight
« Reply #2 on: August 03, 2016, 06:43:08 pm »
An easier (to do and revert) way to attack the backlight pin may be to disconnect the resistor on the sheild, as that is the current limiter for the LED backlight. If you disconnect the end furthest away from the LCD (next to the solderable jumpers/links), you would be able to connect that to an Oak pin (probably through a mosfet or transistor, as I believe the Oak is limited to 12ma source, 20ma sink per pin, and I'm not sure of the power consumption of the backlight).

But yes, you are correct, there is no backlight support int the Adafruit_ILI9341 library... it is just responsible for the graphics support. Backlight manipulation code/support is up the developer/tinkerer :)