Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
learn:courses:unit-3-lab3b:start [2017/02/16 17:07] – [7. LCD Background Information] Marthalearn:courses:unit-3-lab3b:start [2022/10/04 11:38] (current) – external edit 127.0.0.1
Line 1: Line 1:
-====== Lab 3b: LCD Parallel Interface - PMP IO Control ======+====== Lab 3b: LCD Parallel Interface - PMP I/O Control ====== 
 +[[{}/learn/courses/unit-3/start|Back to Unit 3]] 
 +[[{}/learn/courses/unit-3-lab3a/start|Back to Lab 3a]]
 == Download This Document == == Download This Document ==
-  * +{{ :learn:courses:unit-3-lab3b:lab_3b.pdf |Lab 3b PDF}}
  
 ===== 1. Objectives ===== ===== 1. Objectives =====
-  - Develop an application of foreground-background task scheduling. +  - Identify the PIC32 processor pins used for the LCD interface. 
-  - Use change notification interrupts to detect push button presses and releases. +  - Implement LCD control using the PIC32 Parallel Master Port (PMP).  
-  - Eliminate multiple button operations using a timer interrupt to implement a non-blocking delay. +  - Understand handshaking requirements for interfacing two systems operating at differing clock speeds.
-  - Implement the push-on / push off operation using a software-based finite state machine. +
  
 ---- ----
Line 23: Line 23:
 ===== 3. Equipment List ===== ===== 3. Equipment List =====
 ==== 3.1. Hardware ==== ==== 3.1. Hardware ====
-  - Basys MX3 trainer board. +  - [[https://digilent.com/shop/basys-mx3-pic32mx-trainer-board-for-embedded-systems-courses/|Basys MX3 trainer board]] 
-  - PC or Linux Workstation computer. +  - [[https://digilent.com/shop/usb-a-to-micro-b-cable/|Micro USB cable]] 
-  - [[http://store.digilentinc.com/usb-a-to-micro-b-cable/|Micro USB cable]]. +  - Workstation computer running Windows 10 or higher, MAC OS, or Linux 
-  - [[http://store.digilentinc.com/analog-discovery-2-100msps-usb-oscilloscope-logic-analyzer-and-variable-power-supply/|Analog Discovery 2]]. + 
 +In addition, we suggest the following instruments: 
 + 
 +  - [[http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,842,1018&Prod=ANALOG-DISCOVERY|Digilent Analog Discovery 2]]
  
  
 ==== 3.2. Software: ==== ==== 3.2. Software: ====
-  - [[http://www.microchip.com/mplab/mplab-x-ide|Microchip MPLAB X® v3.35 or higher]]. +The following programs must be installed on your development workstation:
-  - [[http://www.microchip.com/SWLibraryWeb/product.aspx?product=PIC32%20Peripheral%20Library|PLIB Peripheral Library]]. +
-  - [[http://store.digilentinc.com/waveforms-2015-download-only/|WaveForms 2015]].+
  
 +  - [[http://www.microchip.com/mplab/mplab-x-ide|Microchip MPLAB X® v3.35 or higher]]
 +  - [[http://www.microchip.com/SWLibraryWeb/product.aspx?product=PIC32%20Peripheral%20Library|PLIB Peripheral Library]]
 +  - [[http://www.microchip.com/xcdemo/xcpluspromo.aspx|XC32 Cross Compiler]]
 +  - [[https://digilent.com/shop/software/digilent-waveforms/|WaveForms]]
  
 ---- ----
  
 ===== 4. Project Takeaways ===== ===== 4. Project Takeaways =====
-  - How to implement a bi-directional parallel IO interface.+  - How to implement a bi-directional parallel I/O interface.
   - How to use delays to control signal timing.   - How to use delays to control signal timing.
   - How to manage ASCII text strings.   - How to manage ASCII text strings.
- 
  
 ---- ----
Line 57: Line 61:
  
 ===== 7. LCD Background Information ===== ===== 7. LCD Background Information =====
-Character [[https://en.wikipedia.org/wiki/Liquid-crystal_display|Liquid Crystal Displays]] (LCD) are low cost electronic devices that are capable of generating visual displays consisting of alphanumeric characters and graphical symbols commonly used for [[https://en.wikipedia.org/wiki/Embedded_system|embedded system]] [[https://en.wikipedia.org/wiki/User_interface|human machine interfaces]] (HMI). Many suppliers of LCD devices are based on the [[https://en.wikipedia.org/wiki/Hitachi_HD44780_LCD_controller|Hitachi HD44780]] LCD controller, and hence have a common hardware and software interface. Some LCD devices have serial interfaces that use UART, I2C, and SPI communications((PmodCLS: Character LCD with Serial Interface, [[http://store.digilentinc.com/pmodcls-character-lcd-with-serial-interface/|http://store.digilentinc.com/pmodcls-character-lcd-with-serial-interface/]])). These protocols are covered in Unit 4. Other LCD devices use interfaces consisting of four or eight data lines and three control lines((PmodCLP Character LCD with Parallel Interface, [[http://store.digilentinc.com/pmodclp-character-lcd-with-parallel-interface/|http://store.digilentinc.com/pmodclp-character-lcd-with-parallel-interface/]])). Although the LCDs that use a serial interface require fewer processor I/O pins, the display controller IC is still based on the Hitachi HD44780, which uses 8 or 11 I/O pins. Hence, the serial LCD devices have an on-board microprocessor that translates the serial communications instructions to parallel I/O. +Character [[https://en.wikipedia.org/wiki/Liquid-crystal_display|Liquid Crystal Displays]] (LCD) are low-cost electronic devices that are capable of generating visual displays consisting of alphanumeric characters and graphical symbols commonly used for [[https://en.wikipedia.org/wiki/Embedded_system|embedded system human machine interfaces]] (HMI). Many suppliers of LCD devices are based on the [[https://en.wikipedia.org/wiki/Hitachi_HD44780_LCD_controller|Hitachi HD44780]] LCD controller, and hence have a common hardware and software interface. Some LCD devices have serial interfaces that use UART, I2C, and SPI communications((PmodCLS: Character LCD with Serial Interface, [[https://digilent.com/shop/pmod-cls-character-lcd-with-serial-interface/]])). These protocols are covered in Unit 4. Other LCD devices use interfaces consisting of four or eight data lines and three control lines((PmodCLP Character LCD with Parallel Interface, [[https://digilent.com/reference/pmod/pmodclp/start]])). Although the LCDs that use a serial interface require fewer processor I/O pins, the display controller IC is still based on the Hitachi HD44780, which uses 8 or 11 I/O pins. Hence, the serial LCD devices have an on-board microprocessor that translates the serial communications instructions to parallel I/O. 
  
-The handshaking required to successfully communicate with the LCD on the Basys MX3 is representative of many common parallel interfaces. +The handshaking required to successfully communicate with the LCD on the Basys MX3 is representative of many common parallel interfaces.
  
  
Line 67: Line 71:
 ===== 8. Lab 3a ===== ===== 8. Lab 3a =====
 ==== 8.1. Requirements ==== ==== 8.1. Requirements ====
-  - All LCD interface pin control will use //LATx//, //LATxSET//, or //LATxCLR// instructions for outputs and //PORTxBITS// for inputs.+  - All LCD interface pin control will use PMP interface as described in the Unit 3 text.
   - Write a library of functions to provide general capability to display strings of text, characters, and numbers at specified positions on the LCD display.    - Write a library of functions to provide general capability to display strings of text, characters, and numbers at specified positions on the LCD display. 
   - All LCD control sequences must meet the strict timing requirements for the following operations:   - All LCD control sequences must meet the strict timing requirements for the following operations:
-    - Initialize the LCD using the recommended sequence of instructions shown in the control flow diagram FIg. B.2. to write specific codes to the LCD at specified intervals.+    - Initialize the LCD using the recommended sequence of instructions to write specific codes to the LCD at specified intervals, shown in the control flow diagram of Fig. B.2.
     - Position the cursor in the display space (Line 1 or Line 2) where the next character is to be displayed.     - Position the cursor in the display space (Line 1 or Line 2) where the next character is to be displayed.
-    - Write function(s) that write ASCII control and display data to the Display Data Ram (DDRAM). one or more? +    - Write function(s) that write ASCII control and display data to the Display Data Ram (DDRAM). 
-    - Translate the ASCII control characters into one or more C instructions for the LCD, as detailed in Table 8.1.+    - Translate the ASCII control characters into one or more C instructions for the LCD as detailed in Table 8.1.
     - Write functions that write ASCII character data to the Display Data Ram (DDRAM).     - Write functions that write ASCII character data to the Display Data Ram (DDRAM).
       - Write a function that will write a single ASCII encoded character to the display.       - Write a function that will write a single ASCII encoded character to the display.
       - Write a function that will write a string (array) of ASCII encoded characters to the display.       - Write a function that will write a string (array) of ASCII encoded characters to the display.
-  - Using the following program, develop a test project that will verify that the function //LCD_puts(byte *str);// correctly displays an array of ASCII text and control characters.<code>+  - Using the following program, develop a test project that will verify that the function LCD_puts(byte *str); correctly displays an array of ASCII text and control characters.<code>
 char test_str[] = “ User generated test string”; char test_str[] = “ User generated test string”;
 int main(void) int main(void)
 { {
- hardware_setup(void); // Initialize the LCD IO pins+ hardware_setup(void); // Initialize the LCD IO pins
  LCD_init(); // Initialize LCD  LCD_init(); // Initialize LCD
  while(1)  while(1)
  {  {
  LCD_puts(test_str); // Display the text string  LCD_puts(test_str); // Display the text string
- DelayMs(1000); // Delay 1 second+ DelayMs(1000); // Delay 1 second
  LCDWrite(0x01); // Clear LCD   LCDWrite(0x01); // Clear LCD
  }  }
 } }
 </code> </code>
-  - Write an application program for the BASYS MX3 processor board that achieves the following:+  - Write an application program for the Basys MX3 processor board that achieves the following:
     - Initializes a loop counter to a value of zero.     - Initializes a loop counter to a value of zero.
     - Displays your name on the first line.     - Displays your name on the first line.
-    - Repositions the cursor to the beginning of the second line and displays the text “LAB 3.”+    - Repositions the cursor to the beginning of the second line and displays the text “Lab 3b.”
     - Repositions the cursor to the eighth character position of the second line.     - Repositions the cursor to the eighth character position of the second line.
     - Displays the value of the loop counter.     - Displays the value of the loop counter.
     - Increments the loop counter.     - Increments the loop counter.
     - Delays one second before repeating steps d through g.     - Delays one second before repeating steps d through g.
 +
  
 **Table 8.1.  LCD controls.** **Table 8.1.  LCD controls.**
Line 109: Line 114:
 ==== 8.2. Design Phase ==== ==== 8.2. Design Phase ====
   - Generate a project in MPLAB X.   - Generate a project in MPLAB X.
-  - Copy the config.bits file to the project directory. +  - Copy the config.bits file to the project directory.
   - Open three new C files: main.c, lcd.c, and swdelay.c.   - Open three new C files: main.c, lcd.c, and swdelay.c.
   - Open two new header files: lcd.h and swdelay.h.   - Open two new header files: lcd.h and swdelay.h.
   - Generate the contents of the main.c file for the initialization code and the infinite loop.   - Generate the contents of the main.c file for the initialization code and the infinite loop.
-  - In swdelay.c, generate a function prototype for the //msDelay(unsigned int dly);// function. +  - In swdelay.c, generate a function prototype for the msDelay(unsigned int dly); function. 
-    - Copy the software delay function from Unit 2, Listing 3 to swdelay.c.+    - Copy the software delay function from Unit 2, Listing 7.3 to swdelay.c.
   - In lcd.h, generate function prototypes for the five LCD functions shown in Fig. B.1.   - In lcd.h, generate function prototypes for the five LCD functions shown in Fig. B.1.
-  - Generate the code for the five LCD functions in lcd.c. +  - Generate the code for the five LCD functions in lcd.c. 
    
 ==== 8.3. Construction Phase ==== ==== 8.3. Construction Phase ====
Line 131: Line 137:
   - List the processor hardware resources that you will be using in this design.   - List the processor hardware resources that you will be using in this design.
   - Generate a data flow diagram that identifies tasks (functions) and the information that needs to be passed between these tasks.   - Generate a data flow diagram that identifies tasks (functions) and the information that needs to be passed between these tasks.
-  - Using the DFD and the multiple CFDs shown in Appendix B, develop and test the functions that will initialize the LCD and display single characters and a string of characters. You should use the? software delay function used in Lab 1b.+  - Using the DFD and the multiple CFDs shown in Appendix B, develop and test the functions that will initialize the LCD and display single characters and a string of characters. You should use the software delay function used in Lab 1b. 
  
 ==== 8.4. Testing ==== ==== 8.4. Testing ====
   - Demonstrate that the test program developed for requirement 4 executes correctly using the test string “\0141234\0115678\0119ABC\r”.   - Demonstrate that the test program developed for requirement 4 executes correctly using the test string “\0141234\0115678\0119ABC\r”.
   - Demonstrate that the test program developed for requirement 5 executes correctly.   - Demonstrate that the test program developed for requirement 5 executes correctly.
 +
  
 ---- ----
  
 ===== 9. Questions ===== ===== 9. Questions =====
 +  - What are the advantages of using the PMP interface over the bit-banging interface?
 +  - What are the advantages of using the bit-banging interface over the PMP interface?
   - How would the LCD display be affected if the application described above is combined with an application that uses interrupts?    - How would the LCD display be affected if the application described above is combined with an application that uses interrupts? 
-  - How can the blocking semaphore represented by the Busy Flag be eliminated? 
   - What is the maximum rate at which characters can be written to the LCD?   - What is the maximum rate at which characters can be written to the LCD?
 +
  
 ---- ----
Line 156: Line 166:
  
 ===== Appendix A: Basys MX3 Schematic Drawings ===== ===== Appendix A: Basys MX3 Schematic Drawings =====
-{{ :learn:courses:unit-3-lab3a:lab3a-figure-a-1.png?nolink |Figure A.1. LCD connection schematic diagram for Labs 3a and 3b.}}+{{ :learn:courses:unit-3-lab3b:lab_3b_3_fig_a_1.jpg?nolink&550 |Figure A.1. LCD connection schematic diagram for Labs 3a and 3b.}}
 //Figure A.1. LCD connection schematic diagram for Labs 3a and 3b.// //Figure A.1. LCD connection schematic diagram for Labs 3a and 3b.//
- 
  
 ---- ----
Line 173: Line 182:
  
 {{ :learn:courses:unit-3-lab3a:lab3a-figure-b-4.png?nolink |Figure B.3. Control flow diagram for LCD Write operation using bit-banging.}} {{ :learn:courses:unit-3-lab3a:lab3a-figure-b-4.png?nolink |Figure B.3. Control flow diagram for LCD Write operation using bit-banging.}}
-//Figure B.3. Control flow diagram for LCD Write operation using bit-banging.//+//Figure B.4. Control flow diagram for LCD Write operation using bit-banging.//
  
 {{ :learn:courses:unit-3-lab3a:lab3a-figure-b-5.png?nolink |Figure B.5. LCD display character control flow diagram.}} {{ :learn:courses:unit-3-lab3a:lab3a-figure-b-5.png?nolink |Figure B.5. LCD display character control flow diagram.}}
 //Figure B.5. LCD display character control flow diagram.// //Figure B.5. LCD display character control flow diagram.//
 +
 +----
 +
 +[[{}/learn/courses/unit-3/start|Back to Unit 3]]
 +[[{}/learn/courses/unit-3-lab3a/start|Back to Lab 3a]]
 +[[{}/learn/courses/unit-4-1/start|Go to Unit 4 Part 1]]
 +