backlight_software.c

 1#include "backlight.h"
 2#include "backlight_driver_common.h"
 3#include "util.h"
 4
 5#ifdef BACKLIGHT_BREATHING
 6#    error "Backlight breathing is not available for software PWM. Please disable."
 7#endif
 8
 9static uint16_t s_duty_pattern = 0;
10
11// clang-format off
12
13/** \brief PWM duty patterns
14 *
15 * We scale the current backlight level to an index within this array. This allows
16 * backlight_task to focus on just switching LEDs on/off, and we can predict the duty pattern
17 */
18static const uint16_t backlight_duty_table[] = {
19    0b0000000000000000,
20    0b1000000000000000,
21    0b1000000010000000,
22    0b1000001000010000,
23    0b1000100010001000,
24    0b1001001001001000,
25    0b1010101010101010,
26    0b1110111011101110,
27    0b1111111111111111,
28};
29#define backlight_duty_table_size ARRAY_SIZE(backlight_duty_table)
30
31// clang-format on
32
33static uint8_t scale_backlight(uint8_t v) {
34    return v * (backlight_duty_table_size - 1) / BACKLIGHT_LEVELS;
35}
36
37void backlight_init_ports(void) {
38    backlight_pins_init();
39}
40
41void backlight_set(uint8_t level) {
42    s_duty_pattern = backlight_duty_table[scale_backlight(level)];
43}
44
45void backlight_task(void) {
46    static uint8_t backlight_tick = 0;
47
48    if (s_duty_pattern & ((uint16_t)1 << backlight_tick)) {
49        backlight_pins_on();
50    } else {
51        backlight_pins_off();
52    }
53    backlight_tick = (backlight_tick + 1) % 16;
54}