Micro c lab6(lcd)
- 1. INTERFACING LCD DISPLAY USING 8051
- 2. Objectives of the Lab Learning pin configurations of 8051 Learning important commands for LCD Learning subroutines for displaying command and data Displaying specific data on LCD.
- 3. Deciding Pins or Ports to use Use with caution If EA high *As LCD needs 11 pins, we will use P2 and P3.
- 4. LCD Keypads are usually used for displaying messages. There are 2 lines and each line can display 16 characters. That’s why it is called 16x2 line display. It is widely used in applications that use MENU or display values. It is a good alternative for SSDs.
- 7. Instructions used in this Lab SETB Px.y CLR Px.y NOP See instruction set for the details of above commands.
- 8. LCD Timing for Read
- 9. LCD Read Subroutine (BF check) LCD read is only needed to check busy flag, to check if LCD is busy. Busy flag is D7. If it is set, the LCD is busy 1. RS=0 2. R/ 𝑊=1 3. E=0 => E=1 4. Stay here if bf=1. There is a passive way to send command or data without checking the BF of LCD. If delay greater than 200 nanoseconds is between the commands or data for LCD, there is no need for BF.
- 10. LCD Timing for Write
- 11. LCD Write subroutine LCD write is used for writing command and/or data to LCD. 1. Move data in A to port where Data pins of LCD are connected. 2. RS=0 for command, RS=1 for data. 3. R/ 𝑊=0 4. E=1 => E=0 5. Check BF or give delay.
- 12. Pin naming and data display Instead of calling pins by their ports, we can also give custom names to pins and use it during code e.g. rs bit p3.5 => setb rs; this means setb p3.5 rw bit p3.6 and en bit p3.7. This is done below ‘org 00h’ and above the rest of the code. For port, mydata equ P2 (pin 2.0 to D0 and so on…) To display character use mov a,#‘X’. To display integer, first make it ASCII, add a,30h. To display a line, use look-up table. line1: db “HELLO WORLD”,0 Soon, we will see the need to append 0 at the end of line.
- 13. Subroutine for Writing Command/Data Label Clear/Set RS Call Delay setb en nop clr en Move command/ data to P2 H to L pulse to enable ret
- 14. Using Lookup Table for display The display of character array is simple, the difficult task is to end that display. For this, we keep a zero at the end of the line and check if the data is zero. mov dptr,#line1 again: mov a,#0 movc a,@a+dptr inc dptr jz exit1; jump if accumulator is zero call data_wrt; subroutine to display single character jmp again exit1: line1: db “Hello World”,0
- 15. Semi-final Pseudo-Code What we have to do to display overall data on LCD is following 1. Define pin and port names 2. Initialize LCD by sending (38h,0Eh,01h followed by command write subroutine) 3. Then data of line1 using lookup table (use data write subroutine) 4. Then data of line2 using lookup table (use data write subroutine) 5. Command Write Subroutine and Data Write Subroutine 6. Delay Subroutine
- 16. Final Pseudo-Code The above Pseudo code works during software test but during hardware we need to add some more steps before step 2. We need to send 030h, commands 3 times with a delay of 50 milli-seconds to initialize the hardware LCD which during software is not needed.
- 17. Proteus Devices needed in this Lab 1. AT89c51 2. 16x2 LCD
- 18. Lab Tasks Display Workstation#XY on line1 and ID numbers on line 2. Quiz Next Week of Keypad and Stepper Motor. Individual Project Briefing during Experiment.