Refresh ePaper displays once code.py is done running

Author: tannewt

main.c

@@ -253,6 +253,7 @@ bool run_code_py(safe_mode_t safe_mode) {
     }
 
     bool serial_connected_before_animation = false;
+    bool refreshed_epaper_display = false;
     rgb_status_animation_t animation;
     prep_rgb_status_animation(&result, found_main, safe_mode, &animation);
     while (true) {
@@ -290,6 +291,13 @@ bool run_code_py(safe_mode_t safe_mode) {
         }
         serial_connected_before_animation = serial_connected();
 
+        // Refresh the ePaper display if we have one. That way it'll show an error message.
+        #if CIRCUITPY_DISPLAYIO
+        if (!refreshed_epaper_display) {
+            refreshed_epaper_display = maybe_refresh_epaperdisplay();
+        }
+        #endif
+
         tick_rgb_status_animation(&animation);
     }
 }

shared-bindings/displayio/__init__.c

@@ -77,7 +77,7 @@
 //|
 //|   Releases any actively used displays so their busses and pins can be used again. This will also
 //|   release the builtin display on boards that have one. You will need to reinitialize it yourself
-//|   afterwards.
+//|   afterwards. This may take seconds to complete if an active EPaperDisplay is refreshing.
 //|
 //|   Use this once in your code.py if you initialize a display. Place it right before the
 //|   initialization so the display is active as long as possible.

shared-module/displayio/EPaperDisplay.c

@@ -170,6 +170,9 @@ void displayio_epaperdisplay_start_refresh(displayio_epaperdisplay_obj_t* self)
 }
 
 uint32_t common_hal_displayio_epaperdisplay_get_time_to_refresh(displayio_epaperdisplay_obj_t* self) {
+    if (self->core.last_refresh == 0) {
+        return 0;
+    }
     // Refresh at seconds per frame rate.
     uint32_t elapsed_time = ticks_ms - self->core.last_refresh;
     if (elapsed_time > self->milliseconds_per_frame) {
@@ -343,6 +346,13 @@ void displayio_epaperdisplay_background(displayio_epaperdisplay_obj_t* self) {
 }
 
 void release_epaperdisplay(displayio_epaperdisplay_obj_t* self) {
+    if (self->refreshing) {
+        wait_for_busy(self);
+        self->refreshing = false;
+        // Run stop sequence but don't wait for busy because busy is set when sleeping.
+        send_command_sequence(self, false, self->stop_sequence, self->stop_sequence_len);
+    }
+
     release_display_core(&self->core);
     if (self->busy.base.type == &digitalio_digitalinout_type) {
         common_hal_digitalio_digitalinout_deinit(&self->busy);
@@ -352,3 +362,20 @@ void release_epaperdisplay(displayio_epaperdisplay_obj_t* self) {
 void displayio_epaperdisplay_collect_ptrs(displayio_epaperdisplay_obj_t* self) {
     displayio_display_core_collect_ptrs(&self->core);
 }
+
+bool maybe_refresh_epaperdisplay(void) {
+    for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
+        if (displays[i].epaper_display.base.type != &displayio_epaperdisplay_type ||
+            displays[i].epaper_display.core.current_group != &circuitpython_splash) {
+            // Skip regular displays and those not showing the splash.
+            continue;
+        }
+        displayio_epaperdisplay_obj_t* display = &displays[i].epaper_display;
+        if (common_hal_displayio_epaperdisplay_get_time_to_refresh(display) != 0) {
+            return false;
+        }
+        return common_hal_displayio_epaperdisplay_refresh(display);
+    }
+    // Return true if no ePaper displays are available to pretend it was updated.
+    return true;
+}

shared-module/displayio/EPaperDisplay.h

@@ -60,6 +60,7 @@ typedef struct {
 
 void displayio_epaperdisplay_background(displayio_epaperdisplay_obj_t* self);
 void release_epaperdisplay(displayio_epaperdisplay_obj_t* self);
+bool maybe_refresh_epaperdisplay(void);
 
 void displayio_epaperdisplay_collect_ptrs(displayio_epaperdisplay_obj_t* self);
 

shared-module/displayio/__init__.c

@@ -54,6 +54,19 @@ void displayio_background(void) {
 }
 
 void common_hal_displayio_release_displays(void) {
+    // Release displays before busses so that they can send any final commands to turn the display
+    // off properly.
+    for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
+        mp_const_obj_t display_type = displays[i].display.base.type;
+        if (display_type == NULL || display_type == &mp_type_NoneType) {
+            continue;
+        } else if (display_type == &displayio_display_type) {
+            release_display(&displays[i].display);
+        } else if (display_type == &displayio_epaperdisplay_type) {
+            release_epaperdisplay(&displays[i].epaper_display);
+        }
+        displays[i].display.base.type = &mp_type_NoneType;
+    }
     for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
         mp_const_obj_t bus_type = displays[i].fourwire_bus.base.type;
         if (bus_type == NULL || bus_type == &mp_type_NoneType) {
@@ -67,17 +80,6 @@ void common_hal_displayio_release_displays(void) {
         }
         displays[i].fourwire_bus.base.type = &mp_type_NoneType;
     }
-    for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
-        mp_const_obj_t display_type = displays[i].display.base.type;
-        if (display_type == NULL || display_type == &mp_type_NoneType) {
-            continue;
-        } else if (display_type == &displayio_display_type) {
-            release_display(&displays[i].display);
-        } else if (display_type == &displayio_epaperdisplay_type) {
-            release_epaperdisplay(&displays[i].epaper_display);
-        }
-        displays[i].display.base.type = &mp_type_NoneType;
-    }
 
     supervisor_stop_terminal();
 }

shared-module/displayio/display_core.c

@@ -52,6 +52,7 @@ void displayio_display_core_construct(displayio_display_core_t* self,
     self->current_group = NULL;
     self->colstart = colstart;
     self->rowstart = rowstart;
+    self->last_refresh = 0;
 
     if (MP_OBJ_IS_TYPE(bus, &displayio_parallelbus_type)) {
         self->bus_reset = common_hal_displayio_parallelbus_reset;
@@ -140,7 +141,7 @@ bool displayio_display_core_show(displayio_display_core_t* self, displayio_group
         if (!circuitpython_splash.in_group) {
             root_group = &circuitpython_splash;
         } else if (self->current_group == &circuitpython_splash) {
-            return false;
+            return true;
         }
     }
     if (root_group == self->current_group) {