diff --git a/lib/ssd1306/ssd1306.h b/lib/ssd1306/ssd1306.h
--- a/lib/ssd1306/ssd1306.h
+++ b/lib/ssd1306/ssd1306.h
@@ -36,8 +36,8 @@ SPI_HandleTypeDef* spi_get();
 void ssd1306_init(void);
 void ssd1306_drawchar(unsigned char ascii, unsigned char row, unsigned char xPos);
 void ssd1306_drawcharbig(unsigned char ascii, unsigned char row, unsigned char xPos);
-void ssd1306_drawstring(const unsigned char *dataPtr, unsigned char row, unsigned char xPos);
-void ssd1306_drawstringbig(const unsigned char *dataPtr, unsigned char row, unsigned char xPos);
+void ssd1306_drawstring(const char *dataPtr, unsigned char row, unsigned char xPos);
+void ssd1306_drawstringbig(const char *dataPtr, unsigned char row, unsigned char xPos);
 void ssd1306_drawlogo();
 void ssd1306_clearscreen();