7 void backlight_init_ports()
10 // Setup PB7 as output and output low.
14 // Use full 16-bit resolution.
17 // I could write a wall of text here to explain... but TL;DW
18 // Go read the ATmega32u4 datasheet.
19 // And this: http://blog.saikoled.com/post/43165849837/secret-konami-cheat-code-to-high-resolution-pwm-on
21 // Pin PB7 = OCR1C (Timer 1, Channel C)
22 // Compare Output Mode = Clear on compare match, Channel C = COM1C1=1 COM1C0=0
23 // (i.e. start high, go low when counter matches.)
24 // WGM Mode 14 (Fast PWM) = WGM13=1 WGM12=1 WGM11=1 WGM10=0
25 // Clock Select = clk/1 (no prescaling) = CS12=0 CS11=0 CS10=1
27 TCCR1A = _BV(COM1C1) | _BV(WGM11); // = 0b00001010;
28 TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001;
33 void backlight_set(uint8_t level)
37 // Turn off PWM control on PB7, revert to output low.
38 TCCR1A &= ~(_BV(COM1C1));
40 // Prevent backlight blink on lowest level
41 PORTB &= ~(_BV(PORTB7));
43 else if ( level == BACKLIGHT_LEVELS )
45 // Prevent backlight blink on lowest level
46 PORTB &= ~(_BV(PORTB7));
47 // Turn on PWM control of PB7
48 TCCR1A |= _BV(COM1C1);
54 // Prevent backlight blink on lowest level
55 PORTB &= ~(_BV(PORTB7));
56 // Turn on PWM control of PB7
57 TCCR1A |= _BV(COM1C1);
59 CHANNEL = 0xFFFF >> ((BACKLIGHT_LEVELS - level) * ((BACKLIGHT_LEVELS + 1) / 2));