diff --git a/main.c b/main.c
index 120a23b..fd9ec7a 100644
--- a/main.c
+++ b/main.c
@@ -52,10 +52,26 @@
 // the I²C address of this slave
 #define I2C_ADDR 0x28
 
+// the functions we can call over I²C
 enum i2c_mode_t {
-	MODE_INSTRUCTION, // read/write instruction/command
-	MODE_DATA, // read/write data
-	MODE_PORT, // read/write 
+	// custom modes
+	MODE_CLEAR_DISPLAY, // clear display
+	MODE_LINE1, // write to line 1
+	MODE_LINE2, // write to line 2
+	MODE_DISPLAY_ON, // turn display on
+	MODE_DISPLAY_OFF, // turn display off
+	MODE_BRIGHTNESS, // set backlight brightness
+
+	// raw instructions, directly mapping to HD44780
+	MODE_DISPLAY,
+	MODE_RETURN_HOME,
+	MODE_ENTRY_MODE_SET,
+	MODE_CURSOR_DISPLAY_SHIFT,
+	MODE_FUNCTION_SET,
+	MODE_CGRAM_ADDR,
+	MODE_DDRAM_ADDR,
+	MODE_DATA,
+
 	MODE_COUNT, // number of modes
 };
 
@@ -269,7 +285,7 @@ void main(void)
 	wait_10us(4 + 1); // wait 37 us (BF could be checked at this point)
 	// we are now for sure in 8-bit more (and could switch do 4-bit). 8-bit mode is actually the default after power up
 	IWDG_KR = IWDG_KR_KEY_REFRESH; // reset watchdog
-	hd44780_write_instruction(0x20); // function set: 4-bit mode
+	hd44780_write_instruction(0x28); // function set (DL=1: 4-bit mode, N=1: 2 lines, F=0: 5x8 dots)
 	hd44780_write_instruction(0x08); // display off
 	hd44780_write_instruction(0x01); // display clear
 	hd44780_write_instruction(0x06); // entry mode set
@@ -289,26 +305,63 @@ void main(void)
 			if (i2c_input_new) { // this is the start of a transaction, the first byte indicates the mode to be used
 				i2c_mode = input_data; // set user provided mode (no need to check since the undefined modes don't do anything)
 				i2c_input_new = false; // clear flag
+				// process mode switch
+				switch (i2c_mode) {
+				case MODE_CLEAR_DISPLAY: // clear display
+					hd44780_write_instruction(0x01); // clear display instruction
+					break;
+				case MODE_LINE1:
+					hd44780_write_instruction(0x80); // set DDRAM address to 0 (line 1)
+					break;
+				case MODE_LINE2:
+					hd44780_write_instruction(0xc0); // set DDRAM address to 0x40 (line 2)
+					break;
+				case MODE_DISPLAY_ON:
+					hd44780_write_instruction(0x0c); // display on
+					break;
+				case MODE_DISPLAY_OFF:
+					hd44780_write_instruction(0x08); // display off
+					break;
+				case MODE_RETURN_HOME:
+					hd44780_write_instruction(0x02); // return home
+					break;
+				default:
+					break; // waiting for data
+				}
 			} else {
 				// process data
 				// note set RS at every byte since read busy always switches it to instruction
 				switch (i2c_mode) {
-				case MODE_PORT:
+				case MODE_LINE1:
+				case MODE_LINE2:
+				case MODE_DATA:
+					hd44780_write_data(input_data);
+					break;
+				case MODE_ENTRY_MODE_SET:
+					hd44780_write_instruction(0x04 | (input_data & 0x3));
+					break;
+				case MODE_DISPLAY:
+					hd44780_write_instruction(0x08 | (input_data & 0x7));
+					break;
+				case MODE_CURSOR_DISPLAY_SHIFT:
+					hd44780_write_instruction(0x10 | (input_data & 0xc));
+					break;
+				case MODE_FUNCTION_SET:
+					hd44780_write_instruction(0x20 | (input_data & 0xc)); // keep DL=0 4-bit mode
+					break;
+				case MODE_CGRAM_ADDR:
+					hd44780_write_instruction(0x40 | (input_data & 0x3f));
+					break;
+				case MODE_DDRAM_ADDR:
+					hd44780_write_instruction(0x80 | (input_data & 0x3f));
+					break;
+				case MODE_BRIGHTNESS:
 					if (input_data) {
 						led_on();
 					} else {
 						led_off();
 					}
 					break;
-				case MODE_INSTRUCTION:
-					if (0x20 == (input_data & 0x20)) { // function set instruction
-						input_data &= ~(1 << 4); // ensure we stay in 4-bit mode
-					}
-					hd44780_write_instruction(input_data);
-					break;
-				case MODE_DATA:
-					hd44780_write_data(input_data);
-					break;
 				default: // read values do not make sense
 					break;
 				}