Initial migration of software PWM backlight (#6709)

* Initial migration of software PWM backlight

* First pass at backlight driver docs

* Correct driver name in docs

* Run backlight_task when using BACKLIGHT_PINS

* Resolve backlight docs TODOs

1 files changed, 66 insertions, 0 deletions

diff --git a/quantum/backlight/backlight_soft.c b/quantum/backlight/backlight_soft.c
new file mode 100644
index 000000000..a6aba7782
--- /dev/null
+++ b/quantum/backlight/backlight_soft.c
@@ -0,0 +1,66 @@
+#include "quantum.h"
+#include "backlight.h"
+
+#if !defined(BACKLIGHT_PIN) && !defined(BACKLIGHT_PINS)
+#    error "Backlight pin/pins not defined. Please configure."
+#endif
+
+#ifdef BACKLIGHT_BREATHING
+#    error "Backlight breathing is not available for software PWM. Please disable."
+#endif
+
+#ifndef BACKLIGHT_ON_STATE
+#    define BACKLIGHT_ON_STATE 0
+#endif
+
+#ifdef BACKLIGHT_PINS
+#    define BACKLIGHT_PIN_INIT BACKLIGHT_PINS
+#else
+#    define BACKLIGHT_PIN_INIT \
+        { BACKLIGHT_PIN }
+#endif
+
+static const pin_t backlight_pins[] = BACKLIGHT_PIN_INIT;
+#define BACKLIGHT_LED_COUNT (sizeof(backlight_pins) / sizeof(pin_t))
+
+#define FOR_EACH_LED(x)                                 \
+    for (uint8_t i = 0; i < BACKLIGHT_LED_COUNT; i++) { \
+        pin_t backlight_pin = backlight_pins[i];        \
+        { x }                                           \
+    }
+
+void backlight_on(pin_t backlight_pin) {
+#if BACKLIGHT_ON_STATE == 0
+    writePinLow(backlight_pin);
+#else
+    writePinHigh(backlight_pin);
+#endif
+}
+
+void backlight_off(pin_t backlight_pin) {
+#if BACKLIGHT_ON_STATE == 0
+    writePinHigh(backlight_pin);
+#else
+    writePinLow(backlight_pin);
+#endif
+}
+
+void backlight_init_ports(void) {
+    // Setup backlight pin as output and output to on state.
+    FOR_EACH_LED(setPinOutput(backlight_pin); backlight_on(backlight_pin);)
+}
+
+void backlight_task(void) {
+    static uint8_t backlight_tick = 0;
+
+    if ((0xFFFF >> (get_backlight_level() * ((BACKLIGHT_LEVELS + 1) / 2))) & (1 << backlight_tick)) {
+        FOR_EACH_LED(backlight_on(backlight_pin);)
+    } else {
+        FOR_EACH_LED(backlight_off(backlight_pin);)
+    }
+    backlight_tick = (backlight_tick + 1) % 16;
+}
+
+void backlight_set(uint8_t level) {
+    // noop as backlight_task uses get_backlight_level()
+}