lcd_send_serial
lcd_send_serial(0x1F); /* R/W=W, RS=0 */
lcd_send_serial(cmd & 0x0F);
lcd_send_serial((cmd >> 4) & 0x0F);
lcd_send_serial(0x5F); /* R/W=W, RS=1 */
lcd_send_serial(data & 0x0F);
lcd_send_serial((data >> 4) & 0x0F);