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

src/backlight.c

@@ -0,0 +1,76 @@
+#include "backlight.h"
+
+static float backlight_duty;
+static float backlight_target_duty;
+static float backlight_step;
+
+static mgos_timer_id backlight_fader_timer_id = 0;
+static mgos_timer_id backlight_keepalive_timer_id = 0;
+
+static void backlight_fader_cb(void *arg) {
+  float new_duty = backlight_duty+backlight_step;
+
+  LOG(LL_DEBUG,("Set backlight from %.2f to %.2f, step %.4f, target %.2f", backlight_duty, new_duty, backlight_step, backlight_target_duty));
+  backlight_duty = new_duty;
+  if (backlight_duty>1.0) backlight_duty=1.0;
+  if (backlight_duty<0.0) backlight_duty=0.0;
+  mgos_pwm_set(mgos_sys_config_get_app_backlight_pin(), BACKLIGHT_PWM_HZ, backlight_duty);
+  if (backlight_step<0 && backlight_duty>backlight_target_duty)
+    return;
+  if (backlight_step>0 && backlight_duty<backlight_target_duty) 
+    return;
+
+  mgos_clear_timer(backlight_fader_timer_id);
+  backlight_fader_timer_id=0;
+  backlight_step=0.0;
+  backlight_target_duty=backlight_duty;
+  LOG(LL_INFO,("Backlight target reached, set at %.2f", backlight_duty));
+  (void) arg;
+}
+
+
+void backlight_set(float new_duty, int fader_msec) {
+  if (new_duty<0.0) backlight_target_duty=0.0;
+  else if (new_duty>1.0) backlight_target_duty=1.0;
+  else backlight_target_duty=new_duty;
+
+  if (backlight_target_duty == backlight_duty)
+    return;
+
+  if (fader_msec == 0) {
+    backlight_duty=backlight_target_duty;
+    backlight_step=0.0;
+    LOG(LL_INFO, ("Setting backlight to %.2f", backlight_duty));
+    mgos_pwm_set(mgos_sys_config_get_app_backlight_pin(), BACKLIGHT_PWM_HZ, backlight_duty);
+    return;
+  }
+
+  backlight_step = (backlight_target_duty - backlight_duty) / ((1000.0*fader_msec)/BACKLIGHT_STEP_USEC);
+  LOG(LL_INFO, ("Changing backlight from %.2f to %.2f in %d msecs, steps of %.4f", backlight_duty, backlight_target_duty, fader_msec, backlight_step));
+  if (backlight_fader_timer_id)
+    mgos_clear_timer(backlight_fader_timer_id);
+  backlight_fader_timer_id = mgos_set_timer(BACKLIGHT_STEP_USEC/1000, true, backlight_fader_cb, NULL);
+}
+
+static void backlight_keepalive_cb(void *arg) {
+  LOG(LL_INFO, ("Inactivity timeout of %d seconds reached, setting backlight off", mgos_sys_config_get_app_inactivity_timeout()));
+  backlight_set(0.0, 1000);
+  (void) arg;
+}
+
+void backlight_keepalive() {
+  if (backlight_keepalive_timer_id)
+    mgos_clear_timer(backlight_keepalive_timer_id);
+  backlight_keepalive_timer_id = mgos_set_timer(mgos_sys_config_get_app_inactivity_timeout()*1000, false, backlight_keepalive_cb, NULL);
+  backlight_set(1.0, 0);
+}
+
+bool backlight_active() {
+  return (backlight_duty>0.0);
+}
+
+
+void backlight_init(void) {
+  backlight_keepalive();
+  return;
+}

src/main.c

@@ -2,6 +2,7 @@
 #include <time.h>
 
 #include "mgos.h"
+#include "mgos_pwm.h"
 #include "tft.h"
 #include "stmpe610.h"
 #include "mongoose-touch.h"
@@ -21,6 +22,23 @@ static void touch_handler(struct mgos_stmpe610_event_data *ed) {
   x = map(ed->x, 0, 4095, 0, _width-1);
   y = map(ed->y, 0, 4095, 0, _height-1);
   LOG(LL_INFO, ("Touch %s at (%d,%d) pressure=%d, length=%d", ed->direction==TOUCH_UP?"UP":"DOWN", x, y, ed->z, ed->length));
+
+  // If the backlight is inactive, grab the TOUCH_DOWN and TOUCH_UP events.
+  // Do nothing on TOUCH_DOWN, but reactivate the backlight by calling
+  // backlight_keepalive() upon TOUCH_UP. This way, the first touch will
+  // wake up the UI, but not send events to widgets and things.
+  if (!backlight_active()) {
+    if (ed->direction==TOUCH_DOWN) {
+      LOG(LL_INFO, ("Ignoring touch event, backlight is inactive"));
+      return;
+    }
+    LOG(LL_INFO, ("Ignoring touch event, but waking up"));
+    backlight_keepalive();
+    return;
+  }
+
+  backlight_keepalive();
+
   widget = screen_widget_find_by_xy(screen, x, y);
 
   if (ed->direction==TOUCH_DOWN) {
@@ -80,6 +98,7 @@ void tft_demo(void)
 enum mgos_app_init_result mgos_app_init(void)
 {
   mgos_stmpe610_set_handler(touch_handler);
+  backlight_init();
 
   tft_demo();