ili9341: added backlight handling via PWM (doesn't work with my displays).

my displays don't accept PWM...

avr/modules/lcd2/ili9341/backlight.asm

@@ -0,0 +1,57 @@
+; ***************************************************************************
+; copyright   : (C) 2026 by Martin Preuss
+; email       : martin@libchipcard.de
+;
+; ***************************************************************************
+; * This file is part of the project "AqHome".                              *
+; * Please see toplevel file COPYING of that project for license details.   *
+; ***************************************************************************
+
+#ifndef AQH_AVR_ILI9341_BACKLIGHT_ASM
+#define AQH_AVR_ILI9341_BACKLIGHT_ASM
+
+; doesn't work with my displays (seems to be binary: either on or off)
+
+;
+; Uses timer 1, set to Fast PWM mode, prescaler 8
+;
+
+Display_BacklightInit:
+  sbi ILI9341_BACKLIGHT_DDR, ILI9341_BACKLIGHT_PIN
+   
+  ldi r16, (1<<COM1A1) | (0<<COM1A0) | (0<<WGM11) | (1<<WGM10)  ; Fast PWM mode, clear pin on match
+  outr TCCR1A, r16
+   
+  ; Prescaler 8, 8-Bit Fast PWM mode
+  ldi r16, (0<<WGM13) | (1<<WGM12) | (0<<CS12) | (1<<CS11) | (0<<CS10);
+
+  ; set to 50 %
+  ldi r16, 0xff
+  clr r17
+
+  outr OCR1AH, r17
+  outr OCR1AL, r16
+
+
+; mode 5: Fast PWM, TOP=OCR1A
+; WGM13: 0
+; WGM12: 1
+; WGM11: 0
+; WGM10: 1
+
+
+
+; @param r16 value to set (0-255)
+
+Display_SetBacklight:
+  clr r17
+  outr OCR1AH, r17
+  outr OCR1AL, r16
+  ret
+; @end
+
+
+
+
+#endif
+