Add backlight dimming after timeout

README.md

@@ -305,6 +305,25 @@ It is recommended to read the value of this register often, or data loss might o
 
 Default value: 0
 
+### Backlight dimming timeout (REG_ID_BK3 = 0x17)
+
+This is a read-write register, it is 1 byte in size.
+
+The value of this register (expressed in units of 500ms) is used to determine when the backlight should be dimmed.
+
+Set to 0 to disable backlight dimming entirely. 
+
+Default value: 0
+
+### Backlight dimming level (REG_ID_BK4 = 0x18)
+
+This is a read-write register, it is 1 byte in size.
+
+The value of this register is used to determine the backlight level when it is the dimmed state. This value has no effect if REG_ID_BK3 is set to 0.
+
+Default value: 96
+
+
 ## Version history
 
 	v1.0:

app/backlight.c

@@ -4,19 +4,71 @@
 #include <hardware/pwm.h>
 #include <pico/stdlib.h>
 
+#define BACKLIGHT_IDLE_POLLING_RATE_MS 500
+
+static struct {
+	uint64_t last_triggered;
+	bool idling;
+	bool alarm_is_set;
+	uint8_t backlight_level;
+} self;
+
 void backlight_sync(void)
 {
-	pwm_set_gpio_level(PIN_BKL, reg_get_value(REG_ID_BKL)  * 0x80);
+	pwm_set_gpio_level(PIN_BKL, self.backlight_level  * 0x80);
+}
+
+static int64_t idle_detector_timer_task(alarm_id_t id, void *user_data)
+{
+	(void)id;
+	(void)user_data;
+
+	uint8_t current_dimming_delay = reg_get_value(REG_ID_BK3);
+	if (current_dimming_delay == 0) {
+		self.idling = true;
+		cancel_alarm(id);
+		self.alarm_is_set = false;
+	} else if (!self.idling && to_ms_since_boot(get_absolute_time()) - self.last_triggered > (current_dimming_delay * 500)) {
+		self.idling = true;
+		cancel_alarm(id);
+		self.alarm_is_set = false;
+		self.backlight_level = reg_get_value(REG_ID_BK4);
+		backlight_sync();
+	}
+	return BACKLIGHT_IDLE_POLLING_RATE_MS * 1000;
+}
+
+void backlight_trigger(void)
+{
+	self.idling = false;
+	self.last_triggered = to_ms_since_boot(get_absolute_time());
+	uint8_t desired_brightness = reg_get_value(REG_ID_BKL);
+	if (self.backlight_level < desired_brightness) {
+		self.backlight_level = desired_brightness;
+		backlight_sync();
+	}
+	if (!self.alarm_is_set) {
+		add_alarm_in_ms(BACKLIGHT_IDLE_POLLING_RATE_MS, idle_detector_timer_task, NULL, true);
+		self.alarm_is_set = true;
+	}
 }
 
 void backlight_init(void)
 {
+	self.idling = false;
 	gpio_set_function(PIN_BKL, GPIO_FUNC_PWM);
 
 	const uint slice_num = pwm_gpio_to_slice_num(PIN_BKL);
 
 	pwm_config config = pwm_get_default_config();
 	pwm_init(slice_num, &config, true);
 
+ 	self.backlight_level = reg_get_value(REG_ID_BKL);
 	backlight_sync();
+	self.last_triggered = 0;
+
+	if (reg_get_value(REG_ID_BK3) > 0) {
+		add_alarm_in_ms(BACKLIGHT_IDLE_POLLING_RATE_MS, idle_detector_timer_task, NULL, true);
+		self.alarm_is_set = true;
+	}
 }

app/backlight.h

@@ -1,6 +1,8 @@
 #pragma once
 
 #include <stdint.h>
+#include <stdbool.h>
 
+void backlight_trigger(void);
 void backlight_sync(void);
 void backlight_init(void);

app/keyboard.c

@@ -1,6 +1,7 @@
 #include "app_config.h"
 #include "fifo.h"
 #include "keyboard.h"
+#include "backlight.h"
 #include "reg.h"
 
 #include <pico/stdlib.h>
@@ -132,7 +133,7 @@ static void transition_to(struct list_item * const p_item, const enum key_state
 
 	if (p_item->effective_key == '\0')
 		return;
-
+	backlight_trigger();
 	keyboard_inject_event(p_item->effective_key, next_state);
 }
 
@@ -210,7 +211,7 @@ static void next_item_state(struct list_item * const p_item, const bool pressed)
 	}
 }
 
-static int64_t timer_task(alarm_id_t id, void *user_data)
+static int64_t idle_detector_timer_task(alarm_id_t id, void *user_data)
 {
 	(void)id;
 	(void)user_data;
@@ -411,5 +412,5 @@ void keyboard_init(void)
 	}
 #endif
 
-	add_alarm_in_ms(reg_get_value(REG_ID_FRQ), timer_task, NULL, true);
+	add_alarm_in_ms(reg_get_value(REG_ID_FRQ), idle_detector_timer_task, NULL, true);
 }

app/reg.c

@@ -49,6 +49,8 @@ void reg_process_packet(uint8_t in_reg, uint8_t in_data, uint8_t *out_buffer, ui
 	case REG_ID_FRQ:
 	case REG_ID_BKL:
 	case REG_ID_BK2:
+	case REG_ID_BK3:
+	case REG_ID_BK4:
 	case REG_ID_GIC:
 	case REG_ID_GIN:
 	case REG_ID_HLD:
@@ -200,6 +202,8 @@ void reg_init(void)
 	reg_set_value(REG_ID_ADR, 0x1F);
 	reg_set_value(REG_ID_IND, 1);	// ms
 	reg_set_value(REG_ID_CF2, CF2_TOUCH_INT | CF2_USB_KEYB_ON | CF2_USB_MOUSE_ON);
+	reg_set_value(REG_ID_BK3, 0); // 500ms units, 0 = no dimming timeout (don't dim)
+	reg_set_value(REG_ID_BK4, 96); 
 
 	touchpad_add_touch_callback(&touch_callback);
 }

app/reg.h

@@ -27,6 +27,8 @@ enum reg_id
 	REG_ID_CF2 = 0x14, // config 2
 	REG_ID_TOX = 0x15, // touch delta x since last read, at most (-128 to 127)
 	REG_ID_TOY = 0x16, // touch delta y since last read, at most (-128 to 127)
+	REG_ID_BK3 = 0x17, // Backlight dimming delay (0 = no dimming, 1 = 500ms, 2 = 1000ms, etc.)
+	REG_ID_BK4 = 0x18, // Backlight dimming level
 
 	REG_ID_LAST,
 };

app/touchpad.c

@@ -1,6 +1,7 @@
 #include "touchpad.h"
 
 #include "keyboard.h"
+#include "backlight.h"
 
 #include <hardware/i2c.h>
 #include <pico/binary_info.h>
@@ -104,6 +105,7 @@ void touchpad_gpio_irq(uint gpio, uint32_t events)
 				}
 			}
 		} else {
+			backlight_trigger();
 			if (self.callbacks) {
 				struct touch_callback *cb = self.callbacks;