Introduction to 4-bit Mode

Till now whatever we discussed in the previous part of ths LCD tutorial, we were dealing with 8-bit mode. Now we are going to learn how to use LCD in 4-bit mode. There are many reasons why sometime we prefer to use LCD in 4-bit mode instead of 8-bit. One basic reason is lesser number of pins are needed to interface LCD.

In 4-bit mode the data is sent in nibbles, first we send the higher nibble and then the lower nibble. To enable the 4-bit mode of LCD, we need to follow special sequence of initialization that tells the LCD controller that user has selected 4-bit mode of operation. We call this special sequence as resetting the LCD. Following is the reset sequence of LCD.
  1. Wait for abour 20mS
  2. Send the first init value (0x30)
  3. Wait for about 10mS
  4. Send second init value (0x30)
  5. Wait for about 1mS
  6. Send third init value (0x30)
  7. Wait for 1mS
  8. Select bus width (0x30 - for 8-bit and 0x20 for 4-bit)
  9. Wait for 1mS

The busy flag will only be valid after the above reset sequence. Usually we do not use busy flag in 4-bit mode as we have to write code for reading two nibbles from the LCD. Instead we simply put a certain ammount of delay usually 300 to 600uS. This delay might vary depending on the LCD you are using, as you might have a different crystal frequency on which LCD controller is running. So it actually depends on the LCD module you are using. So if you feel any problem running the LCD, simply try to increase the delay. This usually works. For me about 400uS works perfect.

LCD connections in 4-bit Mode




Above is the connection diagram of LCD in 4-bit mode, where we only need 6 pins to interface an LCD. D4-D7 are the data pins connection and Enable and Register select are for LCD control pins. We are not using Read/Write (RW) Pin of the LCD, as we are only writing on the LCD so we have made it grounded permanently. If you want to use it.. then you may connect it on your controller but that will only increase another pin and does not make any big difference. Potentiometer RV1 is used to control the LCD contrast. The unwanted data pins of LCD i.e. D0-D3 are connected to ground.

LCD connections in 4-bit Mode

We will now look into the common steps to send data/command to LCD when working in 4-bit mode. As i already explained in 4-bit mode data is sent nibble by nibble, first we send higher nibble and then lower nibble. This means in both command and data sending function we need to saperate the higher 4-bits and lower 4-bits.


The common steps are:
  1. Mask lower 4-bits
  2. Send to the LCD port
  3. Send enable signal
  4. Mask higher 4-bits
  5. Send to LCD port
  6. Send enable signal

We are done with the theory part now, In the next section we will take a look at the programming microcontroller to control LCD in 4-bit mode.

Share it! Like it!

Conversation

ExperimenterUK
Tue Aug 04 2015, 06:04 PM
@ghulamqadir The ESP8266 modules on ebay are cheap and easy to use.
Sat Aug 01 2015, 05:57 AM
ghulamqadir
i want to communitcate wifi module with android phone using pic18f4550. Any Suggestion????????
Sat Aug 01 2015, 05:56 AM
ghulamqadir
Slam
ExperimenterUK
Thu Jul 30 2015, 11:41 PM
@Muhammad Aarshad build what ?
Wed Jul 29 2015, 06:42 PM
Muhammad Aarshad
Hello I want to build it, but I don't know how can I program the micro controller. Can You send me the code of the IC? Thanks in advance My e-mail: [email protected]
Sat Jul 25 2015, 10:37 PM
Arnali
What does the cross means? The ones from pin 7,8,9,10 of the LCD?
Fri Jul 24 2015, 09:53 AM
HARSHAL PATIL
....
shyam
Thu Jul 23 2015, 01:42 PM
hi Ajay
ajay_bhargav
Mon Jul 20 2015, 04:38 AM
@Rohit Biradar, I am glad my tutorial helped
Thu Jul 16 2015, 06:19 PM
Rohit Biradar
Thanks a lot publisher of this tutorial. Everybody tells about the nibble sending methods and the command set for 4-wire lcd interface. You are the first to tell me about the most important part that is resetting the lcd. This thing got me all day. Now I can sleep in peace. Thanks once again. Million thanks.

Downloads

Comments

albatain
Fri Jul 31 2015, 02:58 AM
KDN
Wed Jul 29 2015, 05:14 AM
Tanvir.
Fri Jul 24 2015, 07:59 AM
erummumtaz
Thu Jul 23 2015, 10:47 PM
balvant
Thu Jul 16 2015, 03:56 PM
seoulmak
Mon Jul 13 2015, 01:21 PM
SHIVKHUMAR
Sat Jul 11 2015, 04:10 AM
Nals99
Fri Jul 03 2015, 08:33 AM

Online

Guests: 39, Members: 0 ...

most ever online: 182184
(Members: , Guests: 182184) on 06 Aug 2010: 05:37 AM

Members: 37679
Newest member: albatain
Forum Activity
Mc_Comet32 Avatar
Posted By Mc_Comet32
Sun Jul 26 2015, 05:49 PM
ExperimenterUK Avatar
Posted By ExperimenterUK
Thu Jul 23 2015, 08:14 PM
Try this link.Basically find the tacho output pin...
seoulmak Avatar
Posted By seoulmak
Mon Jul 20 2015, 03:44 PM
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Jul 20 2015, 04:42 AM
Ok then, check if you did not mention "LCD_ClearSc...
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Jul 20 2015, 04:41 AM
I am assuming you're talking about the small CPU f...
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Jul 20 2015, 04:36 AM
Amit Kumar Das Avatar
Posted By Amit Kumar Das
Sun Jul 19 2015, 04:17 AM
Yes they are fine. I have included everything. Una...
seoulmak Avatar
Posted By seoulmak
Fri Jul 17 2015, 08:41 AM
yes, but i need more information to connect the f...
balvant Avatar
Posted By balvant
Thu Jul 16 2015, 04:07 PM
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed Jul 15 2015, 05:42 PM
Is this a project listed on this site ?