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path: root/drivers/backlight/backlight_software.c
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Diffstat (limited to 'drivers/backlight/backlight_software.c')
-rw-r--r--drivers/backlight/backlight_software.c54
1 files changed, 54 insertions, 0 deletions
diff --git a/drivers/backlight/backlight_software.c b/drivers/backlight/backlight_software.c
new file mode 100644
index 0000000000..f2af3e918e
--- /dev/null
+++ b/drivers/backlight/backlight_software.c
@@ -0,0 +1,54 @@
+#include "backlight.h"
+#include "backlight_driver_common.h"
+#include "util.h"
+
+#ifdef BACKLIGHT_BREATHING
+# error "Backlight breathing is not available for software PWM. Please disable."
+#endif
+
+static uint16_t s_duty_pattern = 0;
+
+// clang-format off
+
+/** \brief PWM duty patterns
+ *
+ * We scale the current backlight level to an index within this array. This allows
+ * backlight_task to focus on just switching LEDs on/off, and we can predict the duty pattern
+ */
+static const uint16_t backlight_duty_table[] = {
+ 0b0000000000000000,
+ 0b1000000000000000,
+ 0b1000000010000000,
+ 0b1000001000010000,
+ 0b1000100010001000,
+ 0b1001001001001000,
+ 0b1010101010101010,
+ 0b1110111011101110,
+ 0b1111111111111111,
+};
+#define backlight_duty_table_size ARRAY_SIZE(backlight_duty_table)
+
+// clang-format on
+
+static uint8_t scale_backlight(uint8_t v) {
+ return v * (backlight_duty_table_size - 1) / BACKLIGHT_LEVELS;
+}
+
+void backlight_init_ports(void) {
+ backlight_pins_init();
+}
+
+void backlight_set(uint8_t level) {
+ s_duty_pattern = backlight_duty_table[scale_backlight(level)];
+}
+
+void backlight_task(void) {
+ static uint8_t backlight_tick = 0;
+
+ if (s_duty_pattern & ((uint16_t)1 << backlight_tick)) {
+ backlight_pins_on();
+ } else {
+ backlight_pins_off();
+ }
+ backlight_tick = (backlight_tick + 1) % 16;
+}