add simple work with fonts (too small for this screen), still have some bugs with sprites in lower right corner

F3:F303/NitrogenFlooding/screen.h

@@ -0,0 +1,55 @@
+/*
+ * This file is part of the nitrogen project.
+ * Copyright 2023 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+typedef enum{ // screen states
+     SCREEN_INIT        // init stage
+    ,SCREEN_W4INIT      // wait after last unsuccessfull update
+    ,SCREEN_RELAX       // nothing to do (screen is off)
+    ,SCREEN_CONVBUF     // convert next buffer portion
+    ,SCREEN_UPDATENXT   // update next block
+    ,SCREEN_ACTIVE      // transmission active - wait for SPI transfer ends
+
+} screen_state;
+
+// timeout (ms) in case of SPI error - 100ms
+#define SCRN_SPI_TIMEOUT    (100)
+// wait if failed on init
+#define SCRN_W4INI_TIMEOUT  (1000)
+
+// sprite width and height in pixels
+#define SPRITEWD    (8)
+#define SPRITEHT    (8)
+
+screen_state getScreenState();
+void ClearScreen();
+void UpdateScreen(int y0, int y1);
+void setBGcolor(uint16_t c);
+void setFGcolor(uint16_t c);
+void invertSpriteColor(int xmin, int xmax, int ymin, int ymax);
+void DrawPix(int X, int Y, uint8_t pix);
+uint8_t DrawCharAt(int X, int Y, uint8_t Char);
+int PutStringAt(int X, int Y, const char *str);
+int CenterStringAt(int Y, const char *str);
+int strpixlen(const char *str);
+uint8_t *getScreenBuf();
+void process_screen();
+