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{{Box|type=l_green_light|text=<br />
+
[[Category:8051_tutorials]]
 +
In this tutorial we are going to see how to interface a 2x16 LCD with 8051 in 8-bit mode.
 +
As per the name the 2x16 has 2 lines with 16 chars on each lines. It supports all the ascii chars and is basically used for displaying the alpha numeric characters. Here each character is displayed in a matrix of 5x7 pixels.
 +
Apart from alpha numeric chars it also provides the provision to display the custom characters by creating the pattern.
  
=Introduction:LCD=
 
  
Liquid Crystal Display(LCDs) provide a cost effective way to put a text output unit for a microcontroller. As we have seen in the previous tutorial, LEDs or 7 Segments do no have the flexibility to display informative messages.  
+
=LCD UNIT=
 +
Let us look at a pin diagram of a commercially available LCD like '''JHD162''' which uses a '''HD44780''' controller and then describe its operation.
 +
[[FILE:Pic16f877aLcdInterface.png]]
  
==16x2 LCD==
+
{| class="table table-striped table-hover table-condensed table-bordered"
This display has 2 lines and can display 16 characters on each line. Nonetheless, when it is interfaced with the micrcontroller, we can scroll the messages with software to display information which is more than 16 characters in  length.
+
|-class="info"
 
+
| Pin Number || Symbol || Pin Function
The LCD is a simple device to use but the internal details are complex. Most of the 16x2 LCDs use a '''Hitachi HD44780''' or a compatible controller. Yes, a micrcontroller is present inside a Liquid crystal display as shown in figure 1.
+
[[File:HD44780U Block diagram.png|570x250px|framed|Fig 1: LCD Block diagram]]
+
 
+
The Display Controller takes commands and data from a external microcontroller and drivers the LCD panel'''(LCDP)'''. It takes a ASCII value as input and generate a patter for the dot matrix. E.g., to display letter 'A', it takes its value '''0X41(hex)''' or '''65(dec)''' decodes it into a dot matrix of 5x9 as shown in figure 2.
+
[[File:LCD Animated Turn On.gif|right|framed|Fig2: LCD_turn_on]]
+
It is also possible to generate dot matrix patterns for custom characters and special symbols.
+
 
+
Let us look at a pin diagram of a commercially available LCD like '''JHD162''' which uses a '''HD44780''' controller and then describe its operation.
+
}}
+
{| class="wikitable"
+
 
|-
 
|-
! PIN NUMBER !! FUNCTION
+
|1 || VSS ||Ground
 
|-
 
|-
|1 ||
+
| 2|| VCC || +5v
 
|-
 
|-
| 2||
+
| 3 || VEE || Contrast adjustment (VO)
 
|-
 
|-
| 3 ||
+
| 4 || RS || Register Select. 0:Command, 1: Data
 
|-
 
|-
| 4 ||
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| 5 || R/W || Read/Write, R/W=0: Write & R/W=1: Read
 
|-
 
|-
| 5 ||
+
| 6|| EN || Enable. Falling edge triggered
 
|-
 
|-
| 6||
+
| 7 || D0 || Data Bit 0
 +
|-       
 +
| 8 || D1 || Data Bit 1
 +
|-       
 +
| 9 || D2 || Data Bit 2
 
|-
 
|-
| 7 ||
+
| 10 || D3 || Data Bit 3
 
|-
 
|-
| 8 ||
+
| 11 || D4 || Data Bit 4
 +
|-         
 +
| 12 || D5 || Data Bit 5
 +
|-         
 +
| 13 || D6 || Data Bit 6
 +
|-         
 +
| 14 || D7 || Data Bit 7/Busy Flag
 
|-
 
|-
| 9 ||
+
| 15 || A/LED+ || Back-light Anode(+)
 
|-
 
|-
| 10 ||
+
| 16 || K/LED- || Back-Light Cathode(-)
|-
+
| 11 || 
+
|-
+
| 12 || 
+
|-
+
| 13 || 
+
|-
+
|  14|| 
+
|-
+
|  15|| 
+
|-
+
| 16 || 
+
 
|}
 
|}
 +
<br><br>
  
==Instruction Set==
+
Apart from the voltage supply connections the important pins from the programming perspective are the data lines(8-bit Data bus), Register select, Read/Write and Enable pin.<br><br> 
 +
<b>Data Bus:</b> As shown in the above figure and table, an alpha numeric lcd has a 8-bit data bus referenced as D0-D7.
 +
As it is a 8-bit data bus, we can send the data/cmd to LCD in bytes. It also provides the provision to send the the data/cmd in chunks of 4-bit, which is used when there are limited number of GPIO lines on the microcontroller.<br><br> 
 +
<b>Register Select(RS):</b> The LCD has two register namely a Data register and Command register. Any data that needs to be displayed on the LCD has to be written to the data register of LCD. Command can be issued to LCD by writing it to Command register of LCD.
 +
This signal is used to differentiate the data/cmd received by the LCD.<br>
 +
If the RS signal is <b>LOW</b> then the LCD interprets the 8-bit info as <b>Command</b> and writes it <b>Command register</b> and performs the action as per the command.<br> 
 +
If the RS signal is <b>HIGH</b> then the LCD interprets the 8-bit info as <b>data</b> and copies it to <b>data register</b>. After that the LCD decodes the data for generating the 5x7 pattern and finally displays on the LCD.<br><br> 
 +
<b>Read/Write(RW):</b> This signal is used to write the data/cmd to LCD and reads the  busy flag of LCD.
 +
For write operation the RW should be <b>LOW</b> and for read operation the R/W should be <b>HIGH</b>.<br><br> 
 +
<b>Enable(EN):</b> This pin is used to send the enable trigger to LCD.
 +
After sending the data/cmd, Selecting the data/cmd register, Selecting the Write operation. A HIGH-to-LOW pulse has to be send on this enable pin which will latch the info into the LCD register and triggers the LCD to act accordingly.
 +
<br/>
 +
<br/>
  
The HD44780 instruction set is shown below:
+
=Schematic=
 +
Below schematic shows the minimum connection required for interfacing the LCD with the microcontroller.
 +
<br><br>
  
{|class="wikitable" border="1" cellpadding="10" cellspacing="0" align="center"
+
=Port Connection=
 +
This section shows how to configure the GPIO for interfacing the LCD.<br>
 +
The below configuration is as per the above schematic. You can connect the LCD to any of the PORT pins available on your boards and update this section accordingly
 +
<html>
 +
<script src="https://gist.github.com/SaheblalBagwan/1d7babfd4b67463ce5cf7b4a92f2805e.js"></script>
 +
</html>
 +
<br><br>
  
|+ '''HD44780U based instruction set'''
+
=LCD Operation=
 +
In this section we are going to see how to send the data/cmd to the LCD along with the timing diagrams.
 +
First lets see the timing diagram for sending the data and the command signals(RS,RW,EN), accordingly we write the algorithm and finally the code.
  
|-
+
===Timing Diagram===
 +
The below image shows the timing diagram for sending the data to the LCD.<br>
 +
As shown in the timing diagram  the data is written after sending the RS and RW signals. It is still ok to send the data before these signals.<br>
 +
The only important thing is the data should be available on the databus before generating the High-to-Low pulse on EN pin.
 +
[[File:LCD CmdWrite.jpg|figure: command write]]
 +
<br><br>
  
! style="background: #efefef;" rowspan="2" | Instruction
 
  
! style="background: #efefef;" colspan="10" | Code
+
===Steps for Sending Command:===
 +
*step1: Send the I/P command to LCD.
 +
*step2: Select the Control Register by making RS low.
 +
*step3: Select Write operation making RW low.
 +
*step4: Send a High-to-Low pulse on Enable PIN with some delay_us.
 +
<html>
 +
<script src="https://gist.github.com/SaheblalBagwan/9e8c6f42511355062789a69cace9f980.js"></script>
 +
</html>
 +
<br><br>
  
! style="background: #efefef;" rowspan="2" | Description
+
===Steps for Sending Data:===
 +
*step1: Send the character to LCD.
 +
*step2: Select the Data Register by making RS high.
 +
*step3: Select Write operation making RW low.
 +
*step4: Send a High-to-Low pulse on Enable PIN with some delay_us.
 +
The timings are similar as above only change is that '''RS''' is made high for selecting Data register.
  
|-
+
<html>
 +
<script src="https://gist.github.com/SaheblalBagwan/fd021a189be20644c37541d75de144e4.js"></script>
 +
</html>
 +
<br><br>
  
! style="background: #efefef; border-right: 0px;" | RS
+
=Hardware Connections=
 +
[[File:Lcd8bit.png]]<br>
  
! style="background: #efefef; border-right: 0px; border-left: 0px;" | R/W
+
= Code Examples =
 +
Here is the complete code for displaying the data on 2x16 LCD in 8-bit mode.
 +
<html>
 +
<script src="https://gist.github.com/SaheblalBagwan/1ac04a9ae5112efdbe338f994d7a1af3.js"></script>
 +
</html>
 +
<br><br>
  
! style="background: #efefef; border-right: 0px; border-left: 1px dashed;" | B7
+
=Using Explore Embedded Libraries :=
 +
In the above tutorial we just discussed how to interface 2x16Lcd in 8-bit mode.<br>
 +
Once you know the working of lcd, you can directly use the ExploreEmbedded libraries to play around with your LCD.<br>
 +
For that you need to include the lcd.c/lcd.h and the associated files(delay/stdutils).<br>
 +
After including these files, the only thing you got to do is to configure the PORTs in lcd.h as per your hardware connection.<br>
 +
The below sample code shows how to use the already available LCD functions.
  
! style="background: #efefef; border-right: 0px; border-left: 0px;" | B6
+
==LCD 1x16==
 +
<html>
 +
<script src="https://gist.github.com/SaheblalBagwan/778c519d1babc5659c71086e81da0381.js"></script>
 +
</html>
  
! style="background: #efefef; border-right: 0px; border-left: 0px;" | B5
+
==LCD 2x16==
 +
<html>
 +
<script src="https://gist.github.com/SaheblalBagwan/f75119155d6e79321e222f8b611a6d34.js"></script>
 +
</html>
  
! style="background: #efefef; border-right: 0px; border-left: 0px;" | B4
+
==LCD 4x20==
 +
<html>
 +
<script src="https://gist.github.com/SaheblalBagwan/1b1a7846b1e0376f55bb5aedc8617dfe.js"></script>
 +
</html>
  
! style="background: #efefef; border-right: 0px; border-left: 0px;" | B3
+
[[FILE:01LCD 8bit.png]]
  
! style="background: #efefef; border-right: 0px; border-left: 0px;" | B2
+
=Downloads=
 +
Download the sample code and design files from [https://github.com/ExploreEmbedded/8051_DevelopmentBoard this link].
  
! style="background: #efefef; border-right: 0px; border-left: 0px;" | B1
 
  
! style="background: #efefef; border-left: 0px;" | B0
+
Have a opinion, suggestion , question or feedback about the article let it out here!
 
+
{{DISQUS}}
|-
+
 
+
| Clear display
+
 
+
|align="center" style="border-right: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 1px dashed;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-left: 0px;"| 1
+
 
+
|| Clears display and returns cursor to the home position (address 0).
+
 
+
|-
+
 
+
|| Cursor home
+
 
+
|align="center" style="border-right: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 1px dashed;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 1
+
 
+
|align="center" style="border-left: 0px;"| *
+
 
+
|| Returns cursor to home position. Also returns display being shifted to the original position. DDRAM content remains unchanged.
+
 
+
 
+
|-
+
 
+
|| Entry mode set
+
 
+
|align="center" style="border-right: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 1px dashed;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 1
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| I/D
+
 
+
|align="center" style="border-left: 0px;"| S
+
 
+
|| Sets cursor move direction (I/D); specifies to shift the display (S). These operations are performed during data read/write.
+
 
+
 
+
|-
+
 
+
|| Display on/off control
+
 
+
|align="center" style="border-right: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 1px dashed;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 1
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| D
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| C
+
 
+
|align="center" style="border-left: 0px;"| B
+
 
+
|| Sets on/off of all display (D), cursor on/off (C), and blink of cursor position character (B).
+
 
+
 
+
|-
+
 
+
|| Cursor/display shift
+
 
+
|align="center" style="border-right: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 1px dashed;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 1
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| S/C
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| R/L
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| *
+
 
+
|align="center" style="border-left: 0px;"| *
+
 
+
|| Sets cursor-move or display-shift (S/C), shift direction (R/L). DDRAM content remains unchanged.
+
 
+
 
+
|-
+
 
+
|| Function set
+
 
+
|align="center" style="border-right: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 1px dashed;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 1
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| DL
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| N
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| F
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| *
+
 
+
|align="center" style="border-left: 0px;"| *
+
 
+
|| Sets interface data length (DL), number of display line (N), and character font (F).
+
 
+
 
+
 
+
|-
+
 
+
|| Set CGRAM address
+
 
+
|align="center" style="border-right: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 1px dashed;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 1
+
 
+
|align="center" style="border-left: 0px;" colspan="6"| CGRAM address
+
 
+
|| Sets the CGRAM address. CGRAM data are sent and received after this setting.
+
 
+
 
+
 
+
|-
+
 
+
|| Set DDRAM address
+
 
+
|align="center" style="border-right: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 1px dashed;"| 1
+
 
+
|align="center" style="border-left: 0px;" colspan="7"| DDRAM address
+
 
+
|| Sets the DDRAM address. DDRAM data are sent and received after this setting.
+
 
+
 
+
 
+
|-
+
 
+
|| Read busy flag &<br> address counter
+
 
+
|align="center" style="border-right: 0px;"| 0
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 1
+
 
+
|align="center" style="border-right: 0px; border-left: 1px dashed;"| BF
+
 
+
|align="center" style="border-left: 0px;" colspan="7"| CGRAM/DDRAM address
+
 
+
|| Reads busy flag (BF) indicating internal operation being performed and reads CGRAM or DDRAM address counter contents (depending on previous instruction).
+
 
+
 
+
 
+
|-
+
 
+
|| Write CGRAM or<br> DDRAM
+
 
+
|align="center" style="border-right: 0px;"| 1
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 0
+
 
+
|align="center" style="border-left: 1px dashed;" colspan="8"| Write Data
+
 
+
|| Write data to CGRAM or DDRAM.
+
 
+
 
+
 
+
|-
+
 
+
|| Read from CG/DDRAM
+
 
+
|align="center" style="border-right: 0px;"| 1
+
 
+
|align="center" style="border-right: 0px; border-left: 0px;"| 1
+
 
+
|align="center" style="border-left: 1px dashed;" colspan="8"| Read Data
+
 
+
|| Read data from CGRAM or DDRAM.
+
 
+
|-
+
 
+
|colspan="13" style="font-size: 90%;"| '''Instruction bit names —'''<br>
+
 
+
'''I/D''' - 0 = decrement cursor position, 1 = increment cursor position;
+
 
+
'''S''' - 0 = no display shift, 1 = display shift;
+
 
+
'''D''' - 0 = display off, 1 = display on;
+
 
+
'''C''' - 0 = cursor off, 1 = cursor on;
+
 
+
'''B''' - 0 = cursor blink off, 1 = cursor blink on ;
+
 
+
'''S/C''' - 0 = move cursor, 1 = shift display;
+
 
+
'''R/L''' - 0 = shift left, 1 = shift right;
+
 
+
'''DL''' - 0 = 4-bit interface, 1 = 8-bit interface;
+
 
+
'''N''' - 0 = 1/8 or 1/11 duty (1 line), 1 = 1/16 duty (2 lines);
+
 
+
'''F''' - 0 = 5×8 dots, 1 = 5×10 dots;
+
 
+
'''BF''' - 0 = can accept instruction, 1 = internal operation in progress.
+
 
+
|}
+

Latest revision as of 10:14, 2 September 2016

In this tutorial we are going to see how to interface a 2x16 LCD with 8051 in 8-bit mode. As per the name the 2x16 has 2 lines with 16 chars on each lines. It supports all the ascii chars and is basically used for displaying the alpha numeric characters. Here each character is displayed in a matrix of 5x7 pixels. Apart from alpha numeric chars it also provides the provision to display the custom characters by creating the pattern.


LCD UNIT

Let us look at a pin diagram of a commercially available LCD like JHD162 which uses a HD44780 controller and then describe its operation. Pic16f877aLcdInterface.png

Pin Number Symbol Pin Function
1 VSS Ground
2 VCC +5v
3 VEE Contrast adjustment (VO)
4 RS Register Select. 0:Command, 1: Data
5 R/W Read/Write, R/W=0: Write & R/W=1: Read
6 EN Enable. Falling edge triggered
7 D0 Data Bit 0
8 D1 Data Bit 1
9 D2 Data Bit 2
10 D3 Data Bit 3
11 D4 Data Bit 4
12 D5 Data Bit 5
13 D6 Data Bit 6
14 D7 Data Bit 7/Busy Flag
15 A/LED+ Back-light Anode(+)
16 K/LED- Back-Light Cathode(-)



Apart from the voltage supply connections the important pins from the programming perspective are the data lines(8-bit Data bus), Register select, Read/Write and Enable pin.

Data Bus: As shown in the above figure and table, an alpha numeric lcd has a 8-bit data bus referenced as D0-D7. As it is a 8-bit data bus, we can send the data/cmd to LCD in bytes. It also provides the provision to send the the data/cmd in chunks of 4-bit, which is used when there are limited number of GPIO lines on the microcontroller.

Register Select(RS): The LCD has two register namely a Data register and Command register. Any data that needs to be displayed on the LCD has to be written to the data register of LCD. Command can be issued to LCD by writing it to Command register of LCD. This signal is used to differentiate the data/cmd received by the LCD.
If the RS signal is LOW then the LCD interprets the 8-bit info as Command and writes it Command register and performs the action as per the command.
If the RS signal is HIGH then the LCD interprets the 8-bit info as data and copies it to data register. After that the LCD decodes the data for generating the 5x7 pattern and finally displays on the LCD.

Read/Write(RW): This signal is used to write the data/cmd to LCD and reads the busy flag of LCD. For write operation the RW should be LOW and for read operation the R/W should be HIGH.

Enable(EN): This pin is used to send the enable trigger to LCD. After sending the data/cmd, Selecting the data/cmd register, Selecting the Write operation. A HIGH-to-LOW pulse has to be send on this enable pin which will latch the info into the LCD register and triggers the LCD to act accordingly.

Schematic

Below schematic shows the minimum connection required for interfacing the LCD with the microcontroller.

Port Connection

This section shows how to configure the GPIO for interfacing the LCD.
The below configuration is as per the above schematic. You can connect the LCD to any of the PORT pins available on your boards and update this section accordingly

LCD Operation

In this section we are going to see how to send the data/cmd to the LCD along with the timing diagrams. First lets see the timing diagram for sending the data and the command signals(RS,RW,EN), accordingly we write the algorithm and finally the code.

Timing Diagram

The below image shows the timing diagram for sending the data to the LCD.
As shown in the timing diagram the data is written after sending the RS and RW signals. It is still ok to send the data before these signals.
The only important thing is the data should be available on the databus before generating the High-to-Low pulse on EN pin. figure: command write


Steps for Sending Command:

  • step1: Send the I/P command to LCD.
  • step2: Select the Control Register by making RS low.
  • step3: Select Write operation making RW low.
  • step4: Send a High-to-Low pulse on Enable PIN with some delay_us.



Steps for Sending Data:

  • step1: Send the character to LCD.
  • step2: Select the Data Register by making RS high.
  • step3: Select Write operation making RW low.
  • step4: Send a High-to-Low pulse on Enable PIN with some delay_us.

The timings are similar as above only change is that RS is made high for selecting Data register.



Hardware Connections

Lcd8bit.png

Code Examples

Here is the complete code for displaying the data on 2x16 LCD in 8-bit mode.

Using Explore Embedded Libraries :

In the above tutorial we just discussed how to interface 2x16Lcd in 8-bit mode.
Once you know the working of lcd, you can directly use the ExploreEmbedded libraries to play around with your LCD.
For that you need to include the lcd.c/lcd.h and the associated files(delay/stdutils).
After including these files, the only thing you got to do is to configure the PORTs in lcd.h as per your hardware connection.
The below sample code shows how to use the already available LCD functions.

LCD 1x16

LCD 2x16

LCD 4x20

01LCD 8bit.png

Downloads

Download the sample code and design files from this link.


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