+
+## Software PWM Implementation
+
+When `BACKLIGHT_PIN` is not set to a hardware backlight pin, QMK will use a hardware timer configured to trigger software interrupts. This time will count up to `ICRx` (by default `0xFFFF`) before resetting to 0.
+When resetting to 0, the CPU will fire an OVF (overflow) interrupt that will turn the LEDs on, starting the duty cycle.
+The desired brightness is calculated and stored in the `OCRxx` register. When the counter reaches this value, the CPU will fire a Compare Output match interrupt, which will turn the LEDs off.
+In this way `OCRxx` essentially controls the duty cycle of the LEDs, and thus the brightness, where `0x0000` is completely off and `0xFFFF` is completely on.
+
+The breathing effect is the same as in the hardware PWM implementation.
+
+## Backlight Functions
+
+|Function |Description |
+|----------|-----------------------------------------------------------|
+|`backlight_toggle()` |Turn the backlight on or off |
+|`backlight_enable()` |Turn the backlight on |
+|`backlight_disable()` |Turn the backlight off |
+|`backlight_step()` |Cycle through backlight levels |
+|`backlight_increase()` |Increase the backlight level |
+|`backlight_decrease()` |Decrease the backlight level |
+|`backlight_level(x)` |Sets the backlight level to specified level |
+|`get_backlight_level()` |Return the current backlight level |
+|`is_backlight_enabled()`|Return whether the backlight is currently on |
+
+### Backlight Breathing Functions
+
+|Function |Description |
+|----------|----------------------------------------------------------|
+|`breathing_toggle()` |Turn the backlight breathing on or off |
+|`breathing_enable()` |Turns on backlight breathing |
+|`breathing_disable()` |Turns off backlight breathing |