diff --git a/Core/Inc/SSD1306_oled.h b/Core/Inc/SSD1306_oled.h
index 8a1441c..5e8f0ab 100644
--- a/Core/Inc/SSD1306_oled.h
+++ b/Core/Inc/SSD1306_oled.h
@@ -81,10 +81,9 @@ void SSD1306_display_all(void);
 uint8_t SSD1306_display_page(void);
 void SSD1306_clear(uint8_t color);
 
-void ssd1306_set_pixel(uint8_t x, uint8_t y, uint8_t bw);
-void SSD1306_write_to_buffer(const uint8_t* data, uint8_t width, uint8_t height, int8_t pos_x, int8_t pos_y);
-void ssd1306_clear_buffer (uint8_t width, uint8_t height, uint8_t pos_x, uint8_t pos_y);
-
+void SSD1306_set_pixel(uint8_t x, uint8_t y, uint8_t bw);
+void SSD1306_write_to_buffer(const uint8_t* data, uint8_t width, uint8_t height, int8_t pos_x, int8_t pos_y, uint8_t color);
+void SSD1306_clear_buffer(uint8_t width, uint8_t height, int8_t pos_x, int8_t pos_y, uint8_t color);
 
 #ifdef TEST
 extern uint8_t buffer_oled[SSD1306_BUF_SIZE];
diff --git a/Core/Src/SSD1306_oled.c b/Core/Src/SSD1306_oled.c
index 7599ae2..0b1bed6 100644
--- a/Core/Src/SSD1306_oled.c
+++ b/Core/Src/SSD1306_oled.c
@@ -11,18 +11,18 @@
 
 I2C_HandleTypeDef *oled_i2c;
 
-#ifndef TEST
-static uint8_t buffer_oled[SSD1306_BUF_SIZE];
-#else
+#ifdef TEST
 uint8_t buffer_oled[SSD1306_BUF_SIZE];
+#else
+static uint8_t buffer_oled[SSD1306_BUF_SIZE];
 #endif
 
-void SSD1306_SendCommand(uint8_t cmd)
+static void SSD1306_SendCommand(uint8_t cmd)
 {
 	HAL_I2C_Mem_Write(oled_i2c, SSD1306_ADDRESS<<1, 0x00, 1, &cmd, 1, SSD1306_TIMEOUT);
 }
 
-void SSD1306_SendData(uint8_t *data, uint16_t size)
+static void SSD1306_SendData(uint8_t *data, uint16_t size)
 {
 	HAL_I2C_Mem_Write(oled_i2c, SSD1306_ADDRESS<<1, 0x40, 1, data, size, SSD1306_TIMEOUT);
 }
@@ -130,7 +130,7 @@ void SSD1306_Init(I2C_HandleTypeDef *i2c)
 
 }
 
-void ssd1306_set_pixel(uint8_t x, uint8_t y, uint8_t bw)
+void SSD1306_set_pixel(uint8_t x, uint8_t y, uint8_t bw)
 {
 	if (x > SSD1306_LCDWIDTH || y > SSD1306_LCDHEIGHT) return;
 
@@ -205,37 +205,84 @@ void ssd1306_set_pixel(uint8_t x, uint8_t y, uint8_t bw)
 // 	}
 // }
 
-void ssd1306_clear_buffer (uint8_t width, uint8_t height, uint8_t pos_x, uint8_t pos_y)
+// void ssd1306_clear_buffer (uint8_t width, uint8_t height, uint8_t pos_x, uint8_t pos_y)
+// {
+// 	uint16_t max_x, max_y, index = 0, temp, row = 0;
+// 	if (width + pos_x > SSD1306_LCDWIDTH) max_x = SSD1306_LCDWIDTH;
+// 	else max_x = width + pos_x;
+
+// 	if (height + pos_y > SSD1306_LCDHEIGHT) max_y = SSD1306_LCDHEIGHT;
+// 	else max_y = height + pos_y;
+// 	max_y = max_y / 8 + (max_y % 8 == 0 ? 0 : 1);
+
+// 	uint8_t shift = pos_y % 8;
+// 	uint8_t mask_right = 0xFF >> shift;
+// 	uint8_t mask_left = 0xFF << (8 - shift);
+// 	for (uint8_t y = pos_y / 8; y < max_y; y++, index = width * row)
+// 	{
+// 		for (uint8_t x = pos_x; x < max_x; x++, index++)
+// 		{
+// 			temp = buffer_oled[y * SSD1306_LCDWIDTH + x];
+// 			if (index < width * height/8)
+// 				temp &= mask_left;
+
+// 			if (index >= width)
+// 				temp &= mask_right;
+
+// 			buffer_oled[y * SSD1306_LCDWIDTH + x] = temp;
+// 		}
+// 		row++;
+// 	}
+
+// }
+
+typedef struct 
 {
-	uint16_t max_x, max_y, index = 0, temp, row = 0;
-	if (width + pos_x > SSD1306_LCDWIDTH) max_x = SSD1306_LCDWIDTH;
-	else max_x = width + pos_x;
+	uint16_t bitmap_max_idx;
+	uint8_t buf_row_first;
+	uint8_t buf_row_last;
+	uint8_t buf_col_first;
+	uint8_t buf_col_last;
+	uint8_t bitmap_col;
+	uint8_t bitmap_row;
+	uint8_t bitmap_row_first;
+	uint8_t shift;
+}buf_bitmap_boundry_t;
 
-	if (height + pos_y > SSD1306_LCDHEIGHT) max_y = SSD1306_LCDHEIGHT;
-	else max_y = height + pos_y;
-	max_y = max_y / 8 + (max_y % 8 == 0 ? 0 : 1);
-
-	uint8_t shift = pos_y % 8;
-	uint8_t mask_right = 0xFF >> shift;
-	uint8_t mask_left = 0xFF << (8 - shift);
-	for (uint8_t y = pos_y / 8; y < max_y; y++, index = width * row)
-	{
-		for (uint8_t x = pos_x; x < max_x; x++, index++)
-		{
-			temp = buffer_oled[y * SSD1306_LCDWIDTH + x];
-			if (index < width * height/8)
-				temp &= mask_left;
-
-			if (index >= width)
-				temp &= mask_right;
-
-			buffer_oled[y * SSD1306_LCDWIDTH + x] = temp;
-		}
-		row++;
+static void get_boundry (buf_bitmap_boundry_t* boundry, uint8_t bitmap_width, uint8_t bitmap_height, int8_t pos_x, int8_t pos_y)
+{
+	if (pos_x < 0) {
+		boundry->bitmap_col = pos_x * -1;
+		boundry->buf_col_first = 0;
+	} else {
+		boundry->bitmap_col = 0;
+		boundry->buf_col_first = pos_x;
 	}
 
-}
+	if (pos_y < 0) {
+		boundry->shift = (pos_y * -1);
+		boundry->bitmap_row_first = boundry->shift / 8;
+		boundry->buf_row_first = 0;
+	} else {
+		boundry->shift = pos_y;
+		boundry->bitmap_row_first = 0;
+		boundry->buf_row_first = pos_y / 8;
+	}
 
+	if ((bitmap_width + pos_x) > SSD1306_LCDWIDTH) {
+		boundry->buf_col_last = SSD1306_LCDWIDTH;
+	} else {
+		boundry->buf_col_last = bitmap_width + pos_x;
+	}
+	
+	if (bitmap_height + pos_y > SSD1306_LCDHEIGHT) {
+		boundry->buf_row_last = SSD1306_LCDHEIGHT / 8;
+	} else {
+		boundry->buf_row_last = (bitmap_height + pos_y + 7) / 8;
+	}
+	
+	boundry->bitmap_max_idx = bitmap_width * ((bitmap_height + 7) / 8);
+}
 /**
  * @brief A function that writes a bitmap into the buffer at the given position.
  * 			0,0 -------->x
@@ -248,74 +295,54 @@ void ssd1306_clear_buffer (uint8_t width, uint8_t height, uint8_t pos_x, uint8_t
  * @param bitmap_height Bitmap height in pixels.
  * @param pos_x Position x in the display
  * @param pos_y Position y in the display
+ * @param color WHITE (1) normal mode, others will cause inverse mode
  */
-void SSD1306_write_to_buffer(const uint8_t* bitmap, uint8_t bitmap_width, uint8_t bitmap_height, int8_t pos_x, int8_t pos_y)
+void SSD1306_write_to_buffer(const uint8_t* bitmap, uint8_t bitmap_width, uint8_t bitmap_height, int8_t pos_x, int8_t pos_y, uint8_t color)
 {
 	if (bitmap_width + pos_x < 0 || bitmap_height + pos_y < 0) return;
 
-	uint16_t tmp_buf16, bitmap_idx, bitmap_max_idx;
-	uint8_t buf_row_first, buf_row_last, buf_col_first, buf_col_last;
-	uint8_t bitmap_col, bitmap_row, bitmap_row_first;
-	uint8_t mask_buf, shift;
+	uint16_t tmp_buf16, bitmap_idx;
+	uint8_t mask_buf, tmp_bitmap;
 
-	if (pos_x < 0) {
-		bitmap_col = pos_x * -1;
-		buf_col_first = 0;
-	} else {
-		bitmap_col = 0;
-		buf_col_first = pos_x;
-	}
+	buf_bitmap_boundry_t b;
+	get_boundry(&b, bitmap_width, bitmap_height, pos_x, pos_y);
 
-	if (pos_y < 0) {
-		shift = (pos_y * -1);
-		bitmap_row_first = shift / 8;
-		buf_row_first = 0;
-	} else {
-		shift = pos_y;
-		bitmap_row_first = 0;
-		buf_row_first = pos_y / 8;
-	}
-
-	if ((bitmap_width + pos_x) > SSD1306_LCDWIDTH) {
-		buf_col_last = SSD1306_LCDWIDTH;
-	} else {
-		buf_col_last = bitmap_width + pos_x;
-	}
-	
-	if (bitmap_height + pos_y > SSD1306_LCDHEIGHT) {
-		buf_row_last = SSD1306_LCDHEIGHT / 8;
-	} else {
-		buf_row_last = (bitmap_height + pos_y + 7) / 8;
-	}
-	
-	bitmap_max_idx = bitmap_width * ((bitmap_height + 7) / 8);
-
-	for(uint8_t col = buf_col_first; col < buf_col_last; col++, bitmap_col++)
+	for(uint8_t col = b.buf_col_first; col < b.buf_col_last; col++, b.bitmap_col++)
 	{
 		tmp_buf16 = 0;
-		bitmap_row = bitmap_row_first;
-		for( uint8_t buf_row = buf_row_first; buf_row < buf_row_last; buf_row++, bitmap_row++ )
+		b.bitmap_row = b.bitmap_row_first;
+		for( uint8_t buf_row = b.buf_row_first; buf_row < b.buf_row_last; buf_row++, b.bitmap_row++ )
 		{
-			bitmap_idx = bitmap_width * bitmap_row + bitmap_col;
+			bitmap_idx = bitmap_width * b.bitmap_row + b.bitmap_col;
 			mask_buf = 0;
 
-			if (bitmap_row == 0 && pos_y > 0) {
-				mask_buf |= 0xFF >> (8 - (shift % 8));
+			if (b.bitmap_row == 0 && pos_y > 0) {
+				mask_buf |= 0xFF >> (8 - (b.shift % 8));
 			}
 
-			uint8_t shifted_pixels_left = (pos_y + bitmap_height) - bitmap_row * 8;
+			uint8_t shifted_pixels_left = (pos_y + bitmap_height) - b.bitmap_row * 8;
 			if (shifted_pixels_left < 8) {
 				mask_buf |= (0xFF << shifted_pixels_left);
 			}
 
 			tmp_buf16 |= buffer_oled[buf_row * SSD1306_LCDWIDTH + col] & mask_buf;
 
-			if (bitmap_idx < bitmap_max_idx)
+			if (bitmap_idx < b.bitmap_max_idx)
 			{
+				switch (color)
+				{
+				case WHITE:
+					tmp_bitmap = bitmap[bitmap_idx];
+					break;
+				default:
+					tmp_bitmap = ~(bitmap[bitmap_idx]);
+					break;
+				}
+
 				if (pos_y < 0) {
-					tmp_buf16 |= bitmap[bitmap_idx]  >> (shift % 8);
+					tmp_buf16 |= tmp_bitmap  >> (b.shift % 8);
 				} else {
-					tmp_buf16 |= bitmap[bitmap_idx]  << (shift % 8);
+					tmp_buf16 |= tmp_bitmap  << (b.shift % 8);
 				}
 			}
 
@@ -325,4 +352,57 @@ void SSD1306_write_to_buffer(const uint8_t* bitmap, uint8_t bitmap_width, uint8_
 	}
 }
 
+void SSD1306_clear_buffer(uint8_t width, uint8_t height, int8_t pos_x, int8_t pos_y, uint8_t color)
+{
+	if (width + pos_x < 0 || height + pos_y < 0) return;
 
+	uint16_t tmp_buf16, bitmap_idx;
+	uint8_t mask_buf;
+	
+	switch(color)
+	{
+		case WHITE:
+			color = 0xFF;
+			break;
+		case BLACK:
+			color = 0x00;
+			break;
+	}
+
+	buf_bitmap_boundry_t b;
+	get_boundry(&b, width, height, pos_x, pos_y);
+
+	for(uint8_t col = b.buf_col_first; col < b.buf_col_last; col++, b.bitmap_col++)
+	{
+		tmp_buf16 = 0;
+		b.bitmap_row = b.bitmap_row_first;
+		for( uint8_t buf_row = b.buf_row_first; buf_row < b.buf_row_last; buf_row++, b.bitmap_row++ )
+		{
+			bitmap_idx = width * b.bitmap_row + b.bitmap_col;
+			mask_buf = 0;
+
+			if (b.bitmap_row == 0 && pos_y > 0) {
+				mask_buf |= 0xFF >> (8 - (b.shift % 8));
+			}
+
+			uint8_t shifted_pixels_left = (pos_y + height) - b.bitmap_row * 8;
+			if (shifted_pixels_left < 8) {
+				mask_buf |= (0xFF << shifted_pixels_left);
+			}
+
+			tmp_buf16 |= buffer_oled[buf_row * SSD1306_LCDWIDTH + col] & mask_buf;
+
+			if (bitmap_idx < b.bitmap_max_idx)
+			{
+				if (pos_y < 0) {
+					tmp_buf16 |= color  >> (b.shift % 8);
+				} else {
+					tmp_buf16 |= color  << (b.shift % 8);
+				}
+			}
+
+			buffer_oled[buf_row * SSD1306_LCDWIDTH + col] = (uint8_t) tmp_buf16;
+			tmp_buf16 = tmp_buf16 >> 8;
+		}
+	}
+}
diff --git a/Core/Src/fonts.c b/Core/Src/fonts.c
index b19d9b2..afb32a6 100644
--- a/Core/Src/fonts.c
+++ b/Core/Src/fonts.c
@@ -17,7 +17,7 @@ uint8_t font_print_str(const FONT_INFO * font, uint8_t * text, uint8_t pos_x, ui
 
 	uint8_t width = font_string_lenght_px(font, text);
 
-	ssd1306_clear_buffer(width, height, pos_x, pos_y);
+	SSD1306_clear_buffer(width, height, pos_x, pos_y, WHITE);
 
 	while(*text)
 	{
@@ -27,20 +27,12 @@ uint8_t font_print_str(const FONT_INFO * font, uint8_t * text, uint8_t pos_x, ui
 			continue;
 		}
 
-//		if (actual_char == ' ')
-//		{
-//			x += font->spacePixels + font->interspacePixels;
-//			continue;
-//		}
-
 		uint8_t char_nr = actual_char - font->startChar;
 		const FONT_CHAR_INFO *charinfo =  &font->charInfo[char_nr];
 
-
-		ssd1306_write_to_buffer(font->data + charinfo->offset, charinfo->widthBits, height, x, pos_y);
+		ssd1306_write_to_buffer(font->data + charinfo->offset, charinfo->widthBits, height, x, pos_y, WHITE);
 
 		x += charinfo->widthBits + font->interspacePixels;
-
 	}
 
 	return x;
@@ -56,13 +48,8 @@ uint8_t font_string_lenght_px(const FONT_INFO * font, uint8_t * text)
 		if (actual_char < ' ' || actual_char > 126) {
 			continue;
 		}
-
-//		if (actual_char == ' ') {
-//			x += font->spacePixels + font->interspacePixels;
-//		} else {
-			x += font->charInfo[char_nr].widthBits + font->interspacePixels;
-//		}
-
+		
+		x += font->charInfo[char_nr].widthBits + font->interspacePixels;
 	}
 	return x;
 }
diff --git a/test/support/buffer_oled_expect.c b/test/support/buffer_oled_expect.c
index 31162b7..a3b80c8 100644
--- a/test/support/buffer_oled_expect.c
+++ b/test/support/buffer_oled_expect.c
@@ -558,6 +558,74 @@ const uint8_t posX_minus1_posY_60_8pt[] = {
 	0x1F,0x0F,0x1F,0x1F,0xFF,0x1F,0x1F,0x0F,0xFF,0x0F,0x0F,0x0F,0x0F,0xFF,0x0F,0xFF,
 };
 
+const uint8_t posX_0_posY_0_inverse_8pt[] = { 
+	// res: 128x64   - 1024 bytes
+	0x1F,0xC3,0xDC,0xDC,0xC3,0x1F,0xFF,0x00,0x76,0x76,0x76,0x89,0xFF,0xC3,0xBD,0x7E,
+	0x7E,0x7E,0x7E,0xFF,0x00,0x7E,0x7E,0x7E,0xBD,0xC3,0xFF,0x00,0x76,0x76,0x76,0x7E,
+	0xFF,0x00,0xF6,0xF6,0xF6,0xF6,0xFF,0xC3,0xBD,0x7E,0x6E,0x6E,0x0E,0xFF,0x00,0xF7,
+	0xF7,0xF7,0xF7,0x00,0xFF,0x7E,0x00,0x7E,0xFF,0x7F,0x7E,0x7E,0x80,0xFF,0x00,0xE7,
+	0xDB,0xBD,0x7E,0xFF,0x00,0x7F,0x7F,0x7F,0xFF,0x00,0xFC,0xF3,0xCF,0xF3,0xFC,0x00,
+	0xFF,0x00,0xFC,0xF3,0xCF,0x3F,0x00,0xFF,0xC3,0xBD,0x7E,0x7E,0x7E,0xBD,0xC3,0xFF,
+	0x00,0xEE,0xEE,0xEE,0xF1,0xFF,0x00,0xEE,0xEE,0xCE,0xB1,0x7F,0xFF,0x79,0x76,0x76,
+	0x76,0x8E,0xFF,0xFE,0xFE,0x00,0xFE,0xFE,0xFF,0x80,0x7F,0x7F,0x7F,0x7F,0x80,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+};
+
 const uint8_t picture_16pt[] = { 
 	// res: 128x16   - 256 bytes
 	0x00,0x00,0x00,0xE0,0xFC,0x1F,0x03,0x1F,0xFC,0xE0,0x00,0x00,0x00,0x00,0x00,0xFF,
diff --git a/test/support/buffer_oled_expect.h b/test/support/buffer_oled_expect.h
index 2004e1c..780a6d2 100644
--- a/test/support/buffer_oled_expect.h
+++ b/test/support/buffer_oled_expect.h
@@ -12,6 +12,7 @@ const uint8_t posX_0_posY_minus1_8pt[1024];
 const uint8_t posX_0_posY_minus7_8pt[1024];
 const uint8_t posX_minus1_posY_0_8pt[1024];
 const uint8_t posX_minus1_posY_60_8pt[1024];
+const uint8_t posX_0_posY_0_inverse_8pt[1024];
 
 const uint8_t picture_16pt[256];
 const uint8_t posX_0_posY_0_16pt[1024];
diff --git a/test/test_SSD1306_oled.c b/test/test_SSD1306_oled.c
index 6ef4c6e..6e01923 100644
--- a/test/test_SSD1306_oled.c
+++ b/test/test_SSD1306_oled.c
@@ -20,7 +20,7 @@ void tearDown(void)
 void test_wrtie_to_buffer_at_pos_0_0_height_8pt(void)
 {
     // uint8_t data[8] = {};
-    ssd1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, 0);
+    SSD1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, 0, WHITE);
 
     TEST_ASSERT_EQUAL_UINT8_ARRAY(posX_0_posY_0_8pt, buffer_oled, SSD1306_BUF_SIZE);
     // TEST_ASSERT_EQUAL_UINT8(0xFF, buffer_oled[8]);
@@ -29,14 +29,14 @@ void test_wrtie_to_buffer_at_pos_0_0_height_8pt(void)
 void test_wrtie_to_buffer_at_pos_1_0_height_8pt(void)
 {
     // uint8_t data[8] = {};
-    ssd1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, 1);
+    SSD1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, 1, WHITE);
 
     TEST_ASSERT_EQUAL_UINT8_ARRAY(posX_0_posY_1_8pt, buffer_oled, SSD1306_BUF_SIZE);
 }
 
 void test_wrtie_to_buffer_at_pos_7_0_height_8pt(void)
 {
-    ssd1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, 7);
+    SSD1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, 7, WHITE);
 
     TEST_ASSERT_EQUAL_UINT8_ARRAY(posX_0_posY_7_8pt, buffer_oled, SSD1306_BUF_SIZE);
 }
@@ -44,7 +44,7 @@ void test_wrtie_to_buffer_at_pos_7_0_height_8pt(void)
 void test_wrtie_to_buffer_at_pos_0_0_height_16pt(void)
 {
     // uint8_t data[8] = {};
-    ssd1306_write_to_buffer(picture_16pt, SSD1306_LCDWIDTH, 16, 0, 0);
+    SSD1306_write_to_buffer(picture_16pt, SSD1306_LCDWIDTH, 16, 0, 0, WHITE);
 
     TEST_ASSERT_EQUAL_UINT8_ARRAY(posX_0_posY_0_16pt, buffer_oled, SSD1306_BUF_SIZE);
     // TEST_ASSERT_EQUAL_UINT8(0xFF, buffer_oled[8]);
@@ -53,14 +53,14 @@ void test_wrtie_to_buffer_at_pos_0_0_height_16pt(void)
 void test_wrtie_to_buffer_at_pos_1_0_height_16pt(void)
 {
     // uint8_t data[8] = {};
-    ssd1306_write_to_buffer(picture_16pt, SSD1306_LCDWIDTH, 16, 0, 1);
+    SSD1306_write_to_buffer(picture_16pt, SSD1306_LCDWIDTH, 16, 0, 1, WHITE);
 
     TEST_ASSERT_EQUAL_UINT8_ARRAY(posX_0_posY_1_16pt, buffer_oled, SSD1306_BUF_SIZE);
 }
 
 void test_wrtie_to_buffer_at_pos_7_0_height_16pt(void)
 {
-    ssd1306_write_to_buffer(picture_16pt, SSD1306_LCDWIDTH, 16, 0, 7);
+    SSD1306_write_to_buffer(picture_16pt, SSD1306_LCDWIDTH, 16, 0, 7, WHITE);
 
     TEST_ASSERT_EQUAL_UINT8_ARRAY(posX_0_posY_7_16pt, buffer_oled, SSD1306_BUF_SIZE);
 }
@@ -68,7 +68,7 @@ void test_wrtie_to_buffer_at_pos_7_0_height_16pt(void)
 void test_wrtie_to_buffer_at_pos_0_0_height_12pt(void)
 {
     // uint8_t data[8] = {};
-    ssd1306_write_to_buffer(picture_12pt, SSD1306_LCDWIDTH, 12, 0, 0);
+    SSD1306_write_to_buffer(picture_12pt, SSD1306_LCDWIDTH, 12, 0, 0, WHITE);
 
     TEST_ASSERT_EQUAL_UINT8_ARRAY(posX_0_posY_0_12pt, buffer_oled, SSD1306_BUF_SIZE);
     // TEST_ASSERT_EQUAL_UINT8(0xFF, buffer_oled[8]);
@@ -77,7 +77,7 @@ void test_wrtie_to_buffer_at_pos_0_0_height_12pt(void)
 void test_wrtie_to_buffer_at_pos_1_0_height_12pt(void)
 {
     // uint8_t data[8] = {};
-    ssd1306_write_to_buffer(picture_12pt, SSD1306_LCDWIDTH, 12, 0, 1);
+    SSD1306_write_to_buffer(picture_12pt, SSD1306_LCDWIDTH, 12, 0, 1, WHITE);
 
     TEST_ASSERT_EQUAL_UINT8_ARRAY(posX_0_posY_1_12pt, buffer_oled, SSD1306_BUF_SIZE);
 }
@@ -85,7 +85,7 @@ void test_wrtie_to_buffer_at_pos_1_0_height_12pt(void)
 void test_wrtie_to_buffer_at_pos_0_4_height_12pt(void)
 {
     // uint8_t data[8] = {};
-    ssd1306_write_to_buffer(picture_12pt, SSD1306_LCDWIDTH, 12, 0, 4);
+    SSD1306_write_to_buffer(picture_12pt, SSD1306_LCDWIDTH, 12, 0, 4, WHITE);
 
     TEST_ASSERT_EQUAL_UINT8_ARRAY(posX_0_posY_4_12pt, buffer_oled, SSD1306_BUF_SIZE);
     // TEST_ASSERT_EQUAL_UINT8(0xFF, buffer_oled[8]);
@@ -93,42 +93,49 @@ void test_wrtie_to_buffer_at_pos_0_4_height_12pt(void)
 
 void test_wrtie_to_buffer_at_pos_7_0_height_12pt(void)
 {
-    ssd1306_write_to_buffer(picture_12pt, SSD1306_LCDWIDTH, 12, 0, 7);
+    SSD1306_write_to_buffer(picture_12pt, SSD1306_LCDWIDTH, 12, 0, 7, WHITE);
 
     TEST_ASSERT_EQUAL_HEX8_ARRAY(posX_0_posY_7_12pt, buffer_oled, SSD1306_BUF_SIZE);
 }
 
 void test_wrtie_to_buffer_at_pos_minus1_0_height_8pt(void)
 {
-    ssd1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, -1);
+    SSD1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, -1, WHITE);
 
     TEST_ASSERT_EQUAL_HEX8_ARRAY(posX_0_posY_minus1_8pt, buffer_oled, SSD1306_BUF_SIZE);
 }
 
 void test_wrtie_to_buffer_at_pos_minus7_0_height_8pt(void)
 {
-    ssd1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, -7);
+    SSD1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, -7, WHITE);
 
     TEST_ASSERT_EQUAL_HEX8_ARRAY(posX_0_posY_minus7_8pt, buffer_oled, SSD1306_BUF_SIZE);
 }
 
 void test_wrtie_to_buffer_at_pos_minus8_0_height_8pt(void)
 {
-    ssd1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, -8);
+    SSD1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, -8, WHITE);
 
     TEST_ASSERT_EQUAL_HEX8_ARRAY(buffer_oled, buffer_oled, SSD1306_BUF_SIZE);
 }
 
 void test_wrtie_to_buffer_at_pos_0_minus1_height_8pt(void)
 {
-    ssd1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, -1, 0);
+    SSD1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, -1, 0, WHITE);
 
     TEST_ASSERT_EQUAL_HEX8_ARRAY(posX_minus1_posY_0_8pt, buffer_oled, SSD1306_BUF_SIZE);
 }
 
 void test_wrtie_to_buffer_at_pos_60_minus1_height_8pt(void)
 {
-    ssd1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, -1, 60);
+    SSD1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, -1, 60, WHITE);
 
     TEST_ASSERT_EQUAL_HEX8_ARRAY(posX_minus1_posY_60_8pt, buffer_oled, SSD1306_BUF_SIZE);
+}
+
+void test_wrtie_to_buffer_at_pos_0_0_inverse_height_8pt(void)
+{
+    SSD1306_write_to_buffer(picture_8pt, SSD1306_LCDWIDTH, 8, 0, 0, INVERSE);
+
+    TEST_ASSERT_EQUAL_HEX8_ARRAY(posX_0_posY_0_inverse_8pt, buffer_oled, SSD1306_BUF_SIZE);
 }
\ No newline at end of file