Display Backlight: automatically adjust to ambient sensor reading

This registers a Task, reading the ambient light sensor once aminute and
adjusting the display backlight accordingly

epicardium/main.c

@@ -69,6 +69,23 @@ int main(void)
 		abort();
 	}
 
+	/* Automatically adjust the brightness of the display according to the
+	** light sensor */
+	if (xTaskCreate(
+		    vAutoBrightnessTask,
+		    (const char *)"DisplayBrightness",
+		    configMINIMAL_STACK_SIZE,
+		    NULL,
+		    tskIDLE_PRIORITY + 4,
+		    NULL) != pdPASS) {
+		LOG_CRIT(
+			"startup",
+			"Failed to create %s task!",
+			"vAutoBrightnessTask"
+		);
+		abort();
+	}
+
 	/* MAX30001 */
 	if (xTaskCreate(
 		    vMAX30001Task,
@@ -80,6 +97,7 @@ int main(void)
 		LOG_CRIT("startup", "Failed to create %s task!", "MAX30001");
 		abort();
 	}
+
 	/* API */
 	if (xTaskCreate(
 		    vApiDispatcher,

epicardium/modules/brightness.c

+#include "epicardium.h"
+#include "modules.h"
+#include "log.h"
+
+bool _autobrightness_enabled = true;
+
+void vAutoBrightnessTask(void *pvParameters)
+{
+	vTaskDelay(pdMS_TO_TICKS(500));
+
+	while (1) {
+		vTaskDelay(pdMS_TO_TICKS(60000));
+		if (_autobrightness_enabled) {
+			unsigned short int light;
+
+			while (epic_light_sensor_run() < 0)
+				LOG_CRIT(
+					"autobrightness",
+					"Could not start ambient sensor"
+				);
+
+			while (epic_light_sensor_get(&light) < 0) {
+				LOG_CRIT(
+					"autobrightness",
+					"Could not read light sensor"
+				);
+				vTaskDelay(pdMS_TO_TICKS(500));
+			}
+
+			epic_light_sensor_stop();
+
+			unsigned short int brightness;
+
+			if (light > 199)
+				brightness = 100;
+			else
+				brightness = light / 2 + 1;
+
+			if (epic_disp_open() < 0)
+				continue;
+
+			epic_disp_backlight(brightness);
+			epic_disp_close();
+		}
+	}
+}

epicardium/modules/meson.build

 module_sources = files(
   'bhi.c',
   'bme680.c',
+  'brightness.c',
   'buttons.c',
   'dispatcher.c',
   'display.c',

epicardium/modules/modules.h

@@ -44,6 +44,9 @@ int personal_state_enabled();
 /* ---------- PMIC --------------------------------------------------------- */
 void vPmicTask(void *pvParameters);
 
+/* ---------- Automatically adjust Brightness ------------------------------ */
+void vAutoBrightnessTask(void *pvParameters);
+
 /* ---------- Watchdog ----------------------------------------------------- */
 void watchdog_init();
 void watchdog_clearer_init();