diff --git a/Makefile b/Makefile
index bef08e3..bd8c809 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 CC=gcc
-CFLAGS=-I ./
+CFLAGS=-I ./ -Wall -Werror
 LDFLAGS=-static
 OBJS=main.o ssd1306.o linux_i2c.o
 BIN=ssd1306_bin
diff --git a/linux_i2c.c b/linux_i2c.c
index fcfa337..be95154 100644
--- a/linux_i2c.c
+++ b/linux_i2c.c
@@ -52,8 +52,7 @@ uint8_t _i2c_write(uint8_t* ptr, int16_t len)
 	if (file_i2c == 0 || ptr == 0 || len <= 0)
 		return 1;
 				
-	int32_t rc;
-	rc = write(file_i2c, ptr, len);
+	write(file_i2c, ptr, len);
 	
 	return 0;
 }
@@ -63,8 +62,7 @@ uint8_t _i2c_read(uint8_t *ptr, int16_t len)
 	if (file_i2c == 0 || ptr == 0 || len <= 0)
 		return 1;
 				
-	int32_t rc;
-	rc = read(file_i2c, ptr, len);
+	read(file_i2c, ptr, len);
 
 	return 0;
 }
diff --git a/main.c b/main.c
index 1b0ec69..c1ffc2f 100644
--- a/main.c
+++ b/main.c
@@ -30,9 +30,9 @@ int main(int argc, char **argv)
     uint8_t i2c_node_address = 0;
     int x = -1;
     int y = -1;
-    uint8_t line[25] = {0};
-    uint8_t msg[200] = {0};
-    uint8_t oled_type[10] = {0};
+    char line[25] = {0};
+    char msg[200] = {0};
+    char oled_type[10] = {0};
     int clear_line = -1;
     int clear_all = -1;
     int orientation = -1;
diff --git a/ssd1306.c b/ssd1306.c
index 2590b7c..a03674a 100644
--- a/ssd1306.c
+++ b/ssd1306.c
@@ -12,10 +12,9 @@
 #include <ssd1306.h>
 #include <font.h>
 
-const uint8_t init_oled_type_file[] = "/tmp/.ssd1306_oled_type";
+const char init_oled_type_file[] = "/tmp/.ssd1306_oled_type";
 
 static uint8_t data_buf[1024];
-static int16_t data_len = 0;
 static uint8_t max_lines = 0;
 static uint8_t max_columns = 0;
 static uint8_t global_x = 0;
@@ -309,7 +308,7 @@ uint8_t ssd1306_oled_default_config(uint8_t oled_lines, uint8_t oled_columns)
     return _i2c_write(data_buf, i);
 }
 
-uint8_t ssd1306_oled_write_line(uint8_t size, uint8_t* ptr)
+uint8_t ssd1306_oled_write_line(uint8_t size, char* ptr)
 {
     uint16_t i = 0;
     uint16_t index = 0;
@@ -357,16 +356,16 @@ uint8_t ssd1306_oled_write_line(uint8_t size, uint8_t* ptr)
     return _i2c_write(data_buf, i);
 }
 
-uint8_t ssd1306_oled_write_string(uint8_t size, uint8_t* ptr)
+uint8_t ssd1306_oled_write_string(uint8_t size, char* ptr)
 {
     uint8_t rc = 0;
     
     if (ptr == 0)
         return 1;
     
-    uint8_t* line = 0;
-    uint8_t* cr = 0;
-    uint8_t buf[20];
+    char* line = 0;
+    char* cr = 0;
+    char buf[20];
     
     line = ptr;
     do {
diff --git a/ssd1306.h b/ssd1306.h
index a85d333..cfb3687 100644
--- a/ssd1306.h
+++ b/ssd1306.h
@@ -75,8 +75,8 @@ uint8_t ssd1306_oled_set_Y(uint8_t y);
 uint8_t ssd1306_oled_set_XY(uint8_t x, uint8_t y);
 uint8_t ssd1306_oled_set_rotate(uint8_t degree);
 uint8_t ssd1306_oled_default_config(uint8_t oled_lines, uint8_t oled_columns);
-uint8_t ssd1306_oled_write_line(uint8_t size, uint8_t* ptr);
-uint8_t ssd1306_oled_write_string(uint8_t size, uint8_t* ptr);
+uint8_t ssd1306_oled_write_line(uint8_t size, char* ptr);
+uint8_t ssd1306_oled_write_string(uint8_t size, char* ptr);
 uint8_t ssd1306_oled_clear_line(uint8_t row);
 uint8_t ssd1306_oled_clear_screen();
 uint8_t ssd1306_oled_save_resolution(uint8_t column, uint8_t row);