Backlight support. TOUCH events feed backlight_keepalive(); After a timeout, we fade the backlight to 0 using timers. When the backlight is not active, TOUCH events are not passed to widgets, but the backlight is re-enabled; Add some flags to mos.yml to drive timeout and PWM pin for the backlight on Featherwing

include/backlight.h

@@ -0,0 +1,17 @@
+#ifndef __BACKLIGHT_H
+#define __BACKLIGHT_H
+
+#include "mgos.h"
+#include "mgos_pwm.h"
+#include "mgos_config.h"
+#include "mgos_timers.h"
+
+#define BACKLIGHT_PWM_HZ 10000
+#define BACKLIGHT_STEP_USEC 10000 // 10ms per step.
+
+void backlight_init(void);
+void backlight_set(float new_duty, int fader_msec);
+void backlight_keepalive();
+bool backlight_active();
+
+#endif // __BACKLIGHT_H

include/mongoose-touch.h

@@ -3,6 +3,7 @@
 
 #include "widget.h"
 #include "screen.h"
+#include "backlight.h"
 
 void widget_time_ev(int ev, struct widget_t *w, void *ev_data);