Display Backlight: automatically adjust to ambient sensor reading

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

fixes #95

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();
+		}
+	}
+}

[rahix]

Please use a FreeRTOS software timer for this instead of a task.

[rahix]

I think once a minute is a little slow. Lightlevels can change quite quickly, e.g. when moving from a hackerspace to the "outside world".

[rahix]

The light-sensor is always running in the current firmware. You should not enable/disable it here.

[rahix]

Hmm, this is not really what the display locking/unlocking is supposed to be used for. It would be better to allow epic_disp_backlight() without locking.

[Stefan Haun]

It would, but that needs another change to the display API first, which is outside the scope of this MR.

[genofire]

If you solve it in the API, please think on BLE - https://git.card10.badge.events.ccc.de/card10/firmware/merge_requests/255 .

[rahix]

@genofire This needs to be fixed in BLE as well

[rahix]

Fixed in feb7a097.

[genofire]

done in !255