Add low battery warning screen

Basic UI composition functions have been moved to the main to accomodate
for pre-boot warning screens.

openrtx/src/main.c

@@ -18,17 +18,88 @@
  *   along with this program; if not, see <http://www.gnu.org/licenses/>   *
  ***************************************************************************/
 
+#include <os.h>
+#include <ui.h>
 #include <stdlib.h>
-#include "threads.h"
-#include "platform.h"
+#include <inttypes.h>
+#include <threads.h>
+#include <platform.h>
+#include <battery.h>
+#include <graphics.h>
+#include <hwconfig.h>
+
+/* If battery level is below 0% draw low battery screen, wait and shutdown */
+void check_battery() {
+    OS_ERR os_err;
+
+    // Check battery percentage
+    float vbat = platform_getVbat();
+    float charge = battery_getCharge(vbat);
+
+    // Draw low battery screen
+    if (charge <= 0) {
+        gfx_clearScreen();
+        uint16_t bat_width = SCREEN_WIDTH / 2;
+        uint16_t bat_height = SCREEN_HEIGHT / 3;
+        point_t bat_pos = {SCREEN_WIDTH / 4, SCREEN_HEIGHT / 6};
+        gfx_drawBattery(bat_pos, bat_width, bat_height, 0.1f);
+        point_t text_pos_1 = {0, SCREEN_HEIGHT * 3 / 4};
+        point_t text_pos_2 = {0, SCREEN_HEIGHT * 3 / 4 + 16};
+        const color_t color_white = {255, 255, 255};
+
+        gfx_print(text_pos_1,
+                  "For emergency operation",
+                  FONT_SIZE_6PT,
+                  TEXT_ALIGN_CENTER,
+                  color_white);
+        gfx_print(text_pos_2,
+                  "press any button.",
+                  FONT_SIZE_6PT,
+                  TEXT_ALIGN_CENTER,
+                  color_white);
+        gfx_render();
+
+        // Wait 5 seconds
+        OSTimeDlyHMSM(0u, 0u, 5u, 0u, OS_OPT_TIME_HMSM_STRICT, &os_err);
+
+        // TODO: Shut down radio unless a button is pressed
+    }
+}
 
 int main(void)
 {
+    OS_ERR os_err;
+
     // Initialize platform drivers
     platform_init();
 
+    // Initialize graphics driver
+    gfx_init();
+
+    // Initialize user interface
+    ui_init();
+
+    // Check if battery has enough charge to operate
+    check_battery();
+
+    // Display splash screen
+    ui_drawSplashScreen();
+    gfx_render();
+    while(gfx_renderingInProgress());
+
+    // Wait 30ms before turning on backlight to hide random pixels on screen
+    OSTimeDlyHMSM(0u, 0u, 0u, 30u, OS_OPT_TIME_HMSM_STRICT, &os_err);
+    platform_setBacklightLevel(255);
+
+    // Keep the splash screen for 1 second
+    OSTimeDlyHMSM(0u, 0u, 1u, 0u, OS_OPT_TIME_HMSM_STRICT, &os_err);
+
     // Create OpenRTX threads
     create_threads();
 
-    return 0;
+    // Auxiliary functions loop
+    while(true) {
+        check_battery();
+        OSTimeDlyHMSM(0u, 1u, 0u, 0u, OS_OPT_TIME_HMSM_STRICT, &os_err);
+    }
 }

openrtx/src/threads.c

@@ -79,23 +79,6 @@ static void ui_task(void *arg)
     OS_ERR os_err;
     OS_MSG_SIZE msg_size = 0;
 
-    // Initialize graphics driver
-    gfx_init();
-    // Initialize user interface
-    ui_init();
-
-    // Display splash screen
-    ui_drawSplashScreen();
-    gfx_render();
-    while(gfx_renderingInProgress());
-
-    // Wait 30ms before turning on backlight to hide random pixels on screen
-    OSTimeDlyHMSM(0u, 0u, 0u, 30u, OS_OPT_TIME_HMSM_STRICT, &os_err);
-    platform_setBacklightLevel(255);
-
-    // Keep the splash screen for 1 second
-    OSTimeDlyHMSM(0u, 0u, 1u, 0u, OS_OPT_TIME_HMSM_STRICT, &os_err);
-
     // Get initial state local copy
     OSMutexPend(&state_mutex, 0u, OS_OPT_PEND_BLOCKING, 0u, &os_err);
     state_t last_state = state;