Graphical LCD for beginners and interfacing with PIC MCU
Contents
1. for sending command instruction put the instruction into D then call the subroutine 2 S_ PAGE for sending page number put page no into P then call the subroutine 3 S_LINE for sending line number put line no into L then call the subroutine 4 S DATAI for sending data into 1st half of the LCD put the instruction into D then call the subroutine CS1 is activated and CS2 is deactivated 5 S_DATA2 for sending data into 2nd half of the LCD put the instruction into D then call the subroutine CS2 is activated and CS1 is deactivated For the subroutines 1 amp 2 amp 3 CS1 amp CS2 are both activated in order not to make subroutines for each half of the LCD For 2 amp 3 you can put your page no or line no directly into P or L ex for page no instruction 1s 1011 1XXX and page no is written in the 3 Xs 1 e page 3 instruction 1011 1011 but here write P 3 only Picbasic code using Proton program Device 16F877 XTAL 4 TRISC 00000000 TRISD 00000000 PORTC S00 PORTD 00 Symbol D PORTD D data Symbol DI PORTC 3 sDacta inaLruc ion Jedata USiTnaLZUGIGN Symbol clk PORTC 2 Enable of GLCD clock ve edge Symbol CS1 PORTC 1 Symbol CS2 PORTC 0 Dim P As Byte page number 0 7 Dim L As Byte Line number 0 63 GoSub S_CMD P 1 GoSub S_PAGE L 21 GoSub S_LINE D 0XCO GoSub S_DATAI1 D 0X20 GoSub S_DATAI1 D 0X20 GoSub S_DATA1 D 0X20 GoSub S_DATAI1 D 0XCO GoSub S_DATAI1 P2. and D I configurations 3 Writing Data to the Screen 3 1 Turning the Display RAM On First things first the display needs to be turned on this is done by sending the following instruction to the screen DisplayoN o jo o o i i ft 0 u ft Table 6 Display ON instruction Lets see how to turn on the display using MCU PIC16f877 A by assembly and by Picbasic languages first the LCD is connected as shown in figure 7 Assembly BCF PORTC 2 RC2 0 RS or D I 0 Instruction BCF PORTC 5 gt RCS 0 R W 0 is being written MOVLW 0X3F DB7 DB6 DB5 DB4 DB3 DB2 DBI DBO MOVWE PORTD 0 0 1 1 1 1 1 1 BSF PORTE O 1 1 Clock to pass the PORTE 0 RE0 0 E 0 order to the LCD PicBasic PORTC 2 0 RS or 0 Instruction PORTC 5 0 RAW 0 is being written PORTD 3F DB7 DB6 DBS DB4 DB3 DB2 DBI _ DBO 0 0 1 1 1 1 1 1 PORTE 0 1 RE0 1 E lL Clock to pass the PORTE O 0 gt REO 0 E 0 order to the LCD The reason that I drew this example out and included the code instead of just referring to later sections is so that it is clear how to go from the instruction outlined in Table 6 to performing it assembly or Pic basic 3 2 Placing data on the screen In order to place any information on the screen it is important to understand how the bits control what is on the screen There are 8192 pixels on a 128 X 64 pixel screen divided into 2 halves left and right each half is 64 X64 pixe
3. subroutine for sending command called S_CMD CS1 amp CS2 are both activated in order not to make two different subroutines for each side of the GLCD then clock the E pin The second subroutine for sending data into 1 half of the LCD and called S_DATA1 here we activate CS1 and deactivate CS2 then clock the E pin The third subroutine for sending data into 2 half of the LCD and called S DATA2 and here we activate CS2 and deactivate CS1 then clock the E pin Assembly Code include lt P16F877 inc gt ORG 0X00 GOTO MAIN ORG 0X05 MAIN BSF STATUS RPO BCF STATUS RPI BANK 1 CLRF TRISD CLRF TRISC BCF STATUS RPO BCF STATUS RPI BANKO MOVLW 0 MOVWE PORTD display see 3 1 CALL S_CMD MOVLW 0X55 y address line 21 0101 0101 MOVWE PORTD CALL S_CMD MOVLW OXB9 x address page 1 1011 1001 MOVWE PORTD CALL S_CMD MOVLW 0XCO MOVWE PORTD CALL S_DATA1 MOVLW 0X20 MOVWE PORTD CALL S_DATA1 MOVLW 0X20 MOVWE PORTD CALL S_DATA1 MOVLW 0X20 MOVWE PORTD CALL S_DATA1 MOVLW 0XC0 MOVWF PORTD CALL S_DATA1 MOVLW 0X53 MOVWE PORTD CALL S_CMD MOVLW OXBA MOVWE PORTD CALL S_CMD MOVLW OXFO MOVWE PORTD CALL S_DATA1 MOVLW OXOF MOVWE PORTD CALL S_DATA1 MOVLW OXSA MOVWE PORTD CALL S_CMD MOVLW OXOF MOVWE PORTD CALL S_DATA1 MOVLW OXFO MOVWE PORTD CALL S_DATA1 MOVLW 0X53 MOVWE PORTD CALL S_CMD MOVLW OXBB MOVWE PORTD CALL S_CMD MOVLW 0 01 MOVWE PORTD CALL S_DATAI1 MOVLW OX
4. the medical field as ECG monitors defibrillators ventilators They are used for displaying data pictures shapes graphs real time or fixed trends tables They can be divided into two main categories two color GLCD and color GLCD we will deal with the 2 color LCD through this course I have two targets behind writing these papers 1 to write a basic primer on the operation of any available graphical LCD in our market and 2 describe how to drive it using PIC microcontrollers with assembly and Pic basic languages to be easily used by students in their projects The graphical LCD type I choose was the TOPWAY LM12864LFC 128 x 64 pixel graphical display driven by Samsung KS0108 driver I choose this type especially for 2 reasons 1 I searched the Egyptian market and I found this type in RAM electronics with low coast 2 the KS0108 driver can be easily used 2 The LM12864LFC The LM12864LFC is a 128 x 64 pixel graphical LCD with backlight It is driven by 2 64 x 64 pixel Samsung KS0108 drivers as shown in figure 1 LCD Panel 128x64 pixels 64x64 pixels 64x64 pixels K50108 driver K50108 driver Figure 1 LCD drivers Figure 2 LM12864LFC LCD 2 1 Pin Assignments The LM12864LFC has 20 pins can be classified into 3 groups 1 Power related pins 2 Data bus and 3 Control pins Table 1 contains a detail pin out of the LCD Pin Pin F Negative Power Supply Ground 0V RS H DEQ DEF Dis
5. the paper 2 1 3 Control pins There are 6 control pins which are used to control the operation of the KSO108 hardware drivers and display data on the LCD They are listed m table 4 Pin Symbol Function Typical Value 15 CSI Chip Select I Selects the left KS0108 driver which is also left half of the screen 16 CS2 Chip Select 2 Selects the right KSO108 driver which is also right half of the screen 17 RST Reset set low to reset the display high otherwise 5 R W Read Write set high to read from the LCD to the MCU set low to write from the MCU to the LCD 4 RS or Data Instruction tells the LCD whether or not data is being written to the screen or the MCU is using the data bits to perform an instruction set high for data transfer and set low to designate and instruction is being performed 6 E Enable The enable is used to clock operations to the LCD Table 4 control pins 7 R W and D I are used to determine the mode of operation that the LCD 1s in Table 5 illustrates how these two control bits are used to control operations Enable must be set high and then low in order for an operation to be passed to the LCD DR Bc NNNN An Instruction is being written such as clear the LCD MCU reads the status of the LCD whether it is busy or ready for another command EZ a whatever X Y coordinates have been set Data read the data in the display RAM is read to the MCU Table 5 R W
6. 2 GoSub S_PAGE L 19 GoSub S_LINE D OXFO GoSub S_DATA1 D 0X0F GoSub S_DATA1 L 26 GoSub S_LINE D 0F GoSub S_DATA1 D SF0 GoSub S_DATA1 P 3 GoSub S_PAGE L 19 GoSub S_LINE D 0X01 GoSub S_DATA1 D 0X1E GoSub S_DATA1 D 0X60 GoSub S_DATA1 D 0X80 GoSub S_DATA1 D 0X80 GoSub S_DATA1 D 0X80 GoSub S_DATA1 D 0X60 GoSub S_DATA1 D 0X1E GoSub S_DATA1 D 0X01 GoSub S_DATA1 Stop S_DATA1 CS1 0 CS2 1 DI 1 clk l clk 0 Return S_DATA CS1 1 CS2 0 14 piej 15 GLK 1 clk 0 Return S CMD C51 0 CS 2 0 DI 0 1 1 1 0 Return S PAGE Cs l 0 Co2 0 D P 10111000 x address 1011 1XXX D P 10111000 BI J clk 1 clk 0 Return 5S LINES CS1 0 CS2 0 D L 01000000 address 01XX XXXX D L 601000000 DI 0 clk l clk 0 Return There are a number of commands special for the KSO108 driver in the Proton program which can be used easily these commands are LINE LINETO BOX CIRCLE PLOT UNPLOT refer to proton help First LCD type must be declared as follows LCD_TYPE GRAPHIC Use a Graphic LCD Then each of the data bus RS E CSI CS2 and R W must be declared LCD_DTPORT PORTD LCD_RSPIN PORTC 3 LCD_ENPIN PORTC 2 LCD_CS1PIN PORTC 1 LCD CS2PIN PORTC 0 These decelerations must be written before using any of the above commands R W must be connected to the PIC and declared You can use a standard interfacing circuit with no need for declar
7. D to power up Pin 2 must be connected to 5V Pin 1 must be connected to GND Pn 3 amp Pin 18 must be connected as illustrated in Fig 2 Pin 18 generates 5V as an output and it must be run through a trim pot or voltage divider and fed into Pin 3 This provides the voltage differential of Vdd VO which must be at least 7 5V Adjusting this value adjusts the contrast but the Pins must be connected in this way in order for the image to be seen on the screen if it isn t there is essentially no contrast and nothing will be displayed LM12864L The recommended VR value of VR is 25k to 50k Figure 3 the connection for contrast adjusting Pin 19 amp 20 connects the power needed for backlight Pin 19 5V and Pin 20 GND these pins may be inverted in other models NOTE RST Pin must be high in order to be able to write on the LCD because while the RST is low no instruction can be accepted i e Display off 2 1 2 Data bus There are 8 data bits that provide a number of functions in the operation of the LCD They are the main information carriers to the LCD or called the Data bus They are located on Pins 7 14 with Pin 7 assigned to Data Bit O and Pin 14 assigned to Data Bit 7 Table 3 gives a brief overview of these assignments Symbol Function Typical Value 6 DB2 Data bit 2 7 DB3 Data bit 3 DB4 Data bit 4 9 DB5S___ Databit5 Table 3 Data bus The functions of the data bits will become clearer in later sections of
8. IE MOVWE PORTD CALL S_DATAI1 MOVLW 0X60 MOVWE PORTD CALL S_DATAI1 MOVLW 0X80 MOVWE PORTD CALL S_DATAI1 MOVLW 0X80 MOVWE PORTD CALL S_DATAI1 MOVLW 0X80 MOVWE PORTD CALL S_DATAI1 MOVLW 0X60 MOVWE PORTD CALL S_DATA1 MOVLW OXIE MOVWF PORTD CALL S_DATAI1 MOVLW 0X01 MOVWF PORTD CALL S_DATAI1 HERE GOTO HERE y address line 19 0101 0011 X address page 2 1011 1010 y address line 26 0101 1010 y address line 19 0101 0011 X address page 3 1011 1011 12 13 SUBROTINES S_CMD FOR instructions CS1 amp CS2 must be activated BSF PORTC 0 CSI 1 BCF PORTC I CS2 0 BCF PORTC 3 RS 0 low instruction data BSF PORTC 2 BCF PORTC 2 RETURN S_DATAI FOR DATA one of CS1 amp CS2 only must be activated BSF PORTC 0 CSI 1 BCF PORTC I CS2 0 BSF PORTC 3 RS 1 high RAM data BSF PORTC 2 BCF PORTC 2 RETURN S_DATA2 FOR DATA one of CS1 amp CS2 only must be activated BCF PORTC 0 CS1 0 BSF PORTC 1 CS2 1 BSF PORTC 3 RS 1 high RAM data BSF PORTC 2 BCF PORTC 2 RETURN END 4 2 2 Picbasic Let s take the same example of the assembly we want to draw an ellipse as in figure 8 First the image must be converted into pixels 128X64 pixels maximum see section 4 2 1 I made some symbols to facilitate the program as D is a symbol of port D and so on I also made some variables as P to put page number into it and L for line number Five subroutines are used in this program 1 S_CMD
9. aja il Gad il AJ ama In the name of Allah Graphical LCD for beginners and interfacing with PIC MCU By Eng Mustafa H Abyad Cairo Egypt March 2009 Table of contents Table c 3 EG i dw i kici od Gab O AGO 4 2 The LMI Z564LFC EE Dusia osiada oce ok Gd GG Pt add 4 ZL PM 5 Zakk P wer amp Seine UD DMSO 5 DMZ Data DUS ZNA 6 E ZCODO EDS 6 5 WV pe Data to NE SEFEEN GOW aoi EE 7 3 1 Turning he Display RAM cda Gw i wii Giwi e 7 3 2 PIACING dala on the SETEED acc GE GA W WSSE W ORGA 7 4 Interface WiKPIC ME U ooo O TEN ot doki RE 10 Al Earadwarewo 10 4 2 SOM WAL Cras cas iR RAY snl teases tates RCA EO E 11 4 25KOSSEDDIM Gobi di Odd OO AW GA OS Ai 11 NZZZPICDASIC dci ida EE GEORGE OG EROS OGOL GE ER GA O AG CE 13 Dek PPHCALION NOS ao 17 OZRCIERENCE ac re a 17 1 Introduction Really graphical LCDs are widely used in many applications for different fields such as mobile phones calculators digital oscilloscopes and in
10. ations mentioned above just file must be include at the beginning of the program INCLUDE PROTON_G4 INT For example We want to draw this picture shown in figure 9 Figure 9 picture displayed on GLCD 16 By using interfacing circuit in figure 7 Code Device 16F877 LCD_TYPE GRAPHIC LCD DTPORT PORTD LCD RSPIN PORTC 3 LCD RWPIN PORTC 4 LCD ENPIN PORTC 2 LCD CS1PIN PORTC 1 LCD CS2PIN PORTC 0 Line 1 0 0 127 63 LineTo 1 0 63 LineTo 1 0 0 Box 1 70 32 30 Circle 1 63 32 20 Stop By using the standard interfacing circuit in figure 10 Code Device 16F877 Include PROTON G4 INT Line 1 0 0 127 63 LineTo 1 0 63 LineTo 1 0 0 Box 1 70 32 30 Circle 1 63 32 20 Stop 128 X 64 GLCD SW m Cal a P dk PIC 16F877 E E F F jji VDD 11 or 32 VS6S 172 or 31 Figure 9 standard interfacing circuit 17 5 Application note There must be a delay of at least 1 LCD frequency in between operations or commands of the LCD i e in two places first place after setting DBO 7 CS DI and R W and before toggling enable high and second place between toggling enable high and toggling it low For the LM12864LFC the LCD frequency is not mentioned in datasheet so we can make a delay time of Ims or 1 5ms to be in the safe side This timing can be one of the most common errors because if it is not delayed properly a seemingly good instruction will not provide the desired result This pr
11. g the Y address 2 Setting the X address 3 Sending data Figure 6 gives an example of writing data of 8 pixels on the LCD The Y address actually has a counter so it need only be set once and then every time there is a data write it will be incremented to the next line e Xx page 0 MEJ TT TT NC address is set E 856X page s LL PORTD 0b 10101010 then the picture DBO to the left is an accurate s d Hp BE representation Xx page 1 appear on the amp _ EE ee m Y address sa W JE gt Figure 6 a zoomed in version of Figure 5 it also gives an example of how a pixel is written If the Y address is set to 34 X page is set to 0 and a data write instruction is given with PORTD 0b10101010 then the pixels in those locations will be dark This is the basic idea of placing data on the LCD but how can you implement these 3 steps and how the LCD knows the Y and X axes you want to write in There are special instructions for setting column Y address setting page X address and writing data on the display table 7 shows these instructions Se wl 0 a o Function Set column 0 1 Y address 0 63 Set column address into the Y address counter Y address Set page 00 1 1 Set page address into the X address register X address 0 7 Write data Data 8 pixels Write disp
12. l which is divided into 8 pages X axis each page is 8 X 64 pixels divided into 64 column Y axis Each column is 8 pixels vertically from DO to D7 and so data is entered 8 pixels by 8 pixels Figure 4 and Figure 5 show how the screen is broken down into its X and Y axes Fig 4 shows the left half of the screen if CS1 is 1 and CS2 is 0 The Y address refers to which line the pixels should be written to and the X page sets the column to which they will be written to Page X LCD Display front view D7 EAEE E NE EEN SONES EE EEA E 128x64 piels oe Column Y Address 00h gt 3Fh 0 gt 64 00h gt 3Fh 0 gt 64 Chip Select C51 1 CS2 0 CSi1 0 CS2 1 Figure 4 show how the screen is broken down into X and Y axes for each of the 2 halves LCD CS1 1 0 Next figure CS2 0 a z EEE A page U through 3 each made of 8 pixels z through DBO 2 i 012345676910 55 56 57 58 5960 61 62 63 Y Address setY pixel Figure 5 illustrates how the left half or right half if CS2 I and CSI 0 works The Y address determines what Y line the pixels will be placed on the X page determines which of the eight vertical 8 pixel strips the pixels will be placed on and the Data bits of the write data instruction will the be places across the X page on the specified Y line There are three basic steps that must be done in order to determine where the pixels will go l Settin
13. lay data into display data RAM Then Y address counter increases by I automatically 4 Instructions 2 DB7 i Table 7 display control instructions 10 Now I think that our 1 target was verified and the operation of the LCD became clear the following section will describes interfacing of the LCD with MCU PIC and how to drive it using PIC 4 Interfacing with PIC MCU 4 1 Hardware Figure 7 shows the connection between the LCD and the PIC that we will build on the software programs This is not a standard connection you can make any other one suitable for the requirements of your project 128 X 64 GLCD PIC 16F877 VDD 11 or 32 VSS 172 or 31 Figure 7 interfacing schematic LCD Pins PIC 16F877 Pins Data bus DBO Table 8 interfacing connections 11 4 2 Software In this section we will show how to write a software program by assembly and Picbasic languages for interfacing the GLCD with the PIC 4 2 1 Assembly We want to draw an ellipse as shown in figure 8 Figure 8 ellipse displayed on GLCD First the image must be converted into pixels 128X64 pixels maximum I converted it using a program called Bmp2asm that covert the image into hex numbers in a text file I downloaded the program from the internet Second write the program as follows using MPLAB program Put the data display data or instruction data on port D then call each of three subroutines the first
14. oblem may not be appear in software simulation as Proteus but take care while implementing your hardware from this point 6 References 1 Lucas L Delaney Design of a Graphical LCD Driver and Educational LCD Primer Design Project Report 2 LM12864LFC LCD user manual 3 Proton manual ai dans ai bme_mabyad yahoo com
15. play RAM data RS L DBO DEF Instruction data 5 RW Input In read mode E Input RAN H Data read form the LED module data appears at DEO DE and can be read by the host while E H and the device is being selected In write mode Ry L Data write to the LCD module data appears at DBO DE will be written into the LCD module at E HL and device is being selected 7 DBO VO Data bus or r Thre state I O terminal for display data or instruction data 15 C51 Input Chip selection When Czi 1 enable access to tha Left Sida 54 column of tha LCD modula 16 CS2 Input Chip selection enable access tha Right Sida 64 columnioftha LCD modula 17 RST Reset signal RST L Display off display start line register becomes 0 no command or instruction data could be accepted RST H Normal running VOUT wer Boo 0 Positive Power for LED backlight Negative Power for LED backlight Table 1 a detail pin out of the LCD 2 1 1 Power amp Setting up pins The important pins for this section are as follows Pin Symbol Function Typical Value 2 VDD Supply voltage connect to 5V 1 VSS GND Ground connect to ground Operating voltage Connect through pot as 1s described below VOUT Negative Voltage output outputs 5V connect to pot Power supply for backlight Power supply for backlight Table 2 Power amp Setting up pins 6 In order for the LC
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