The 7735 backlight consists of a number of LEDs which are turned on by pulling the 7735 backlight control pin (PA1) low and off by pulling it high.
It is possible to “dim” LEDs by applying a PWM signal which modulates their duty cycle. In this section, we show how to configure a timer to allow the intensity of the 7735 backlight to be modified under program control. The library code to configure timers is in stm32f10x_tim