BacklightPwmCtrl_enum Struct Reference

Type of backlight control for the LCD. More...

#include <lcd_base.h>

Detailed Description

Type of backlight control for the LCD.

When the selected type is Constant, the pin is simply on or off - there is no gradation in the intensity of the display. In this case any free pin can be used to control the backlight. On the other hand, when PWM is used to control brightness, take care to use only PWM-able mbed pins (p21, p22, p23, p24, p25, and p26), any other pins won't work. It is assumed that you know what you are doing, so no check is done to prevent using a non-PWM pin as assigned control pin, when either Direct or Indirect option is used.

Version:

0.1

Remarks:

When choosing PWM to control the backlight, you have the option to choose the pin to either source (Direct) or sink (Indirect) the current for LCD brightness control. Be aware that the mbed pins can source (and probably sink when configured as inputs) only 4 mA @+3V3 VDD. So if you are intending to use a bigger LCD, whith more LEDs in its backlight implementation, you probably want to interface it through a small signal transistor or a small MOSFET, in order to be able to handle a higher current without damaging your mbed.

As of version 0.1 (2013-01-25) the Indirect method of PWM has not been implemented yet.