diff -r cf91a3a20d0d -r 7b134c27fadb main/calibration.c
--- a/main/calibration.c	Sun May 19 21:05:07 2019 +0200
+++ b/main/calibration.c	Mon Jul 01 23:15:49 2019 +0200
@@ -41,9 +41,9 @@
 {
     _fg = TFT_ORANGE;
     TFT_setFont(DEJAVU24_FONT, NULL);
-    TFT_print("Scherm calibratie", CENTER, 60);
+    TFT_print((char *)"Scherm calibratie", CENTER, 60);
     TFT_setFont(DEJAVU18_FONT, NULL);
-    TFT_print("Druk op de oplichtende stippen", CENTER, 90);
+    TFT_print((char *)"Druk op de oplichtende stippen", CENTER, 90);
 }
 
 
@@ -113,7 +113,7 @@
 
     TFT_fillScreen(TFT_BLACK);
     TFT_setFont(DEJAVU18_FONT, NULL);
-    TFT_print("Scherm calibratie is klaar.", CENTER, 60);
+    TFT_print((char *)"Scherm calibratie is klaar.", CENTER, 60);
     /*
      * Calculate the new calibration values.
      * The testdots were 10 pixels of the corners, 
@@ -128,7 +128,7 @@
     TS_set_calibration(config.ts_xleft, config.ts_xright, config.ts_ytop, config.ts_ybottom);
     write_config();
 
-    Buttons_Add(130, 200, 60, 40, "Ok", 0);
+    Buttons_Add(130, 200, 60, 40, (char *)"Ok", 0);
     Buttons_Show();
     while (1) {
 	vTaskDelay(20 / portTICK_PERIOD_MS);