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Graphical 128x64 UEXT Display backlight control?


#1

I have the Graphical 128x64 UEXT Display hooked up to a FEZ domino that I just received. Is there any way to programatically control the backlight, or is the 3.3V hard wired to it? If hardwired, is there documentation on the pinout of the UEXT port so that an interface circuit to vary the backlight could be made? Thanks,

Dean


#2

http://www.tinyclr.com/downloads/Extension/FEZ-Disp_Exp.pdf

From schematics above, it is connected directly to VCC but you can disconnect the backlight cable and then connected to your own circuitry that has some transistor to control the backlight.


#3

dkie: I put some info about this on the character LCDs here, under "Controlling backlight with the microcontroller ": (link removed)

A basic transistor and resistor (available at your local awesome electronics supplier, or, worse case scenario, an RadioShack :slight_smile: is used to drive the backlight with minimal current consumption on the FEZ.

PWM allows you to cleanly the backlight from 0 to nearly 100% of the backlight supply voltage. (Some is lost by using the transistor)

I believe you can also control the LCD contrast using a digital potentiometer (I2C would be freakin’ easy!), if the current consumption is near zil, though I have not tried this.