diff options
Diffstat (limited to 'keyboard/preonic/backlight.c')
| -rw-r--r-- | keyboard/preonic/backlight.c | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/keyboard/preonic/backlight.c b/keyboard/preonic/backlight.c new file mode 100644 index 0000000000..f69364b2af --- /dev/null +++ b/keyboard/preonic/backlight.c @@ -0,0 +1,61 @@ + +#include <avr/io.h> +#include "backlight.h" + +#define CHANNEL OCR1C + +void backlight_init_ports() +{ + + // Setup PB7 as output and output low. + DDRB |= (1<<7); + PORTB &= ~(1<<7); + + // Use full 16-bit resolution. + ICR1 = 0xFFFF; + + // I could write a wall of text here to explain... but TL;DW + // Go read the ATmega32u4 datasheet. + // And this: http://blog.saikoled.com/post/43165849837/secret-konami-cheat-code-to-high-resolution-pwm-on + + // Pin PB7 = OCR1C (Timer 1, Channel C) + // Compare Output Mode = Clear on compare match, Channel C = COM1C1=1 COM1C0=0 + // (i.e. start high, go low when counter matches.) + // WGM Mode 14 (Fast PWM) = WGM13=1 WGM12=1 WGM11=1 WGM10=0 + // Clock Select = clk/1 (no prescaling) = CS12=0 CS11=0 CS10=1 + + TCCR1A = _BV(COM1C1) | _BV(WGM11); // = 0b00001010; + TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001; + + backlight_init(); +} + +void backlight_set(uint8_t level) +{ + if ( level == 0 ) + { + // Turn off PWM control on PB7, revert to output low. + TCCR1A &= ~(_BV(COM1C1)); + CHANNEL = 0x0; + // Prevent backlight blink on lowest level + PORTB &= ~(_BV(PORTB7)); + } + else if ( level == BACKLIGHT_LEVELS ) + { + // Prevent backlight blink on lowest level + PORTB &= ~(_BV(PORTB7)); + // Turn on PWM control of PB7 + TCCR1A |= _BV(COM1C1); + // Set the brightness + CHANNEL = 0xFFFF; + } + else + { + // Prevent backlight blink on lowest level + PORTB &= ~(_BV(PORTB7)); + // Turn on PWM control of PB7 + TCCR1A |= _BV(COM1C1); + // Set the brightness + CHANNEL = 0xFFFF >> ((BACKLIGHT_LEVELS - level) * ((BACKLIGHT_LEVELS + 1) / 2)); + } +}
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