diff --git a/include/effect_big_clock.h b/include/effect_big_clock.h
index 1ea08db..acbb35f 100644
--- a/include/effect_big_clock.h
+++ b/include/effect_big_clock.h
@@ -13,9 +13,9 @@ class BigClockEffect : public Effect {
 
     void drawText(char *text, int x, int y, CRGB color);
 
-    unsigned char* font_char(unsigned char* font, char c);
+    const unsigned char* font_char(const unsigned char* font, char c);
 
-    void drawSprite(unsigned char* sprite, int xOffset, int yOffset, CRGB color);
+    void drawSprite(const unsigned char* sprite, int xOffset, int yOffset, CRGB color);
 
   public:
     void loop();
diff --git a/include/text.h b/include/text.h
index f3b3623..a88f5c7 100644
--- a/include/text.h
+++ b/include/text.h
@@ -3,7 +3,7 @@
 
 #include "functions.h"
 
-static unsigned char font5x7[] = {
+const unsigned char font5x7[] = {
   0x00, 0x00, 0x00, 0x00, 0x00,// (space)
   0x00, 0x00, 0x5F, 0x00, 0x00,// !
   0x00, 0x07, 0x00, 0x07, 0x00,// "
@@ -102,7 +102,7 @@ static unsigned char font5x7[] = {
   0x08, 0x1C, 0x2A, 0x08, 0x08 // <-
 };
 
-static unsigned char numbers4x7[] = {
+const unsigned char numbers4x7[] = {
   0x3E, 0x51, 0x45, 0x3E,// 0
   0x00, 0x42, 0x7F, 0x40,// 1
   0x42, 0x61, 0x49, 0x46,// 2
@@ -115,7 +115,7 @@ static unsigned char numbers4x7[] = {
   0x06, 0x49, 0x29, 0x1E // 9
 };
 
-static unsigned char numbers3x5[] = {
+const unsigned char numbers3x5[] = {
   B01110, B10001, B01110, // 0
   B01000, B11111, B00000, // 1
   B01001, B10011, B01101, // 2
@@ -128,12 +128,12 @@ static unsigned char numbers3x5[] = {
   B11101, B10101, B11111, // 9
 };
 
-void drawTextSprite(Window window, unsigned char* sprite, int w, int h, int xPos, int yPos, CRGB color, boolean invert);
+void drawTextSprite(Window window, const unsigned char* sprite, int w, int h, int xPos, int yPos, CRGB color, boolean invert);
 
-void drawChar(Window window, unsigned char* font, int w, int h, int x, int y, char c, CRGB color);
+void drawChar(Window window, const unsigned char* font, int w, int h, int x, int y, char c, CRGB color);
 
-void drawDigit(Window window, unsigned char* font, int w, int h, int x, int y, int digit, CRGB color, boolean invert);
+void drawDigit(Window window, const unsigned char* font, int w, int h, int x, int y, int digit, CRGB color, boolean invert);
 
-void drawText(Window window, char *font, int w, int h, char *text, int x, int y, CRGB color);
+void drawText(Window window, const char *font, int w, int h, char *text, int x, int y, CRGB color);
 
 #endif
diff --git a/src/effect_big_clock.cpp b/src/effect_big_clock.cpp
index 4407337..5ec3df2 100644
--- a/src/effect_big_clock.cpp
+++ b/src/effect_big_clock.cpp
@@ -16,11 +16,11 @@ void BigClockEffect::drawText(char *text, int x, int y, CRGB color) {
   }
 }
 
-unsigned char* BigClockEffect::font_char(unsigned char* font, char c) {
-  return &font[(c - 48) * 4];
+const unsigned char* BigClockEffect::font_char(const unsigned char* font, char c) {
+  return font + (c - 48) * 4;
 }
 
-void BigClockEffect::drawSprite(unsigned char* sprite, int xOffset, int yOffset, CRGB color) {
+void BigClockEffect::drawSprite(const unsigned char* sprite, int xOffset, int yOffset, CRGB color) {
   for ( byte y = 0; y < 7; y++) {
     for ( byte x = 0; x < 4; x++) {
       bool on = (sprite[x] >> y & 1) * 255;
diff --git a/src/text.cpp b/src/text.cpp
index 82d3911..3be4340 100644
--- a/src/text.cpp
+++ b/src/text.cpp
@@ -1,7 +1,7 @@
 #include "functions.h"
 #include "text.h"
 
-void drawTextSprite(Window window, unsigned char* sprite, int w, int h, int xPos, int yPos, CRGB color, boolean invert) {
+void drawTextSprite(Window window, const unsigned char* sprite, int w, int h, int xPos, int yPos, CRGB color, boolean invert) {
   for (byte y=0; y<h; y++) for (byte x=0; x<w; x++) {
     bool on = (sprite[x]>>(h-1-y)&1)*255;
     if (invert) on = !on;
@@ -9,17 +9,17 @@ void drawTextSprite(Window window, unsigned char* sprite, int w, int h, int xPos
   }
 }
 
-void drawChar(Window window, unsigned char* font, int w, int h, int x, int y, char c, CRGB color) {
-  unsigned char* sprite = &font[(c-32)*w];
+void drawChar(Window window, const unsigned char* font, int w, int h, int x, int y, char c, CRGB color) {
+  const unsigned char* sprite = &font[(c-32)*w];
   drawTextSprite(window, sprite, w, h, x, y, color, false);
 }
 
-void drawDigit(Window window, unsigned char* font, int w, int h, int x, int y, int digit, CRGB color, boolean invert) {
-  unsigned char* sprite = &font[digit*w];
+void drawDigit(Window window, const unsigned char* font, int w, int h, int x, int y, int digit, CRGB color, boolean invert) {
+  const unsigned char* sprite = &font[digit*w];
   drawTextSprite(window, sprite, w, h, x, y, color, invert);
 }
 
-void drawText(Window window, char *font, int w, int h, char *text, int x, int y, CRGB color) {
+void drawText(Window window, const char *font, int w, int h, char *text, int x, int y, CRGB color) {
   for (uint16_t i = 0; i < strlen(text); i++) {
     drawChar(window, font5x7, 5, 7, x+i*(w+1), y, text[i], color);
   }