Getting acquainted with the development tools June 27, 2006 ELE492 Embedded System Design Exercise 1

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1 Getting acquainted with the development tools June 27, 2006 ELE492 Embedded System Design Exercise 1 Overview In this first exercise, a few tasks are given to get acquainted with the PIC microcontroller and the development tools we will use in this class throughout the semester. The first task will step through the creation of a project inside of the MPLAB IDE (integrated development environment). Next, additional configuration parameters are set in the project for the particular device we are using. The third task goes through the process of adding the source code for the first exercise. The fourth task involves building the circuit provided to view the operation of the code entered. Lastly, the source code is compiled and downloaded to the PIC for verification. Upon completion of the guided tour of the environment and the PIC microcontroller, an assignment is given to extrapolate upon the learned material. Task 1 - Using the Project Wizard to create a project To start off this task, we will start the Project Wizard to help create and configure some parameters of our project. The Project Wizard is started from the menus by clicking Project -> Project Wizard. The following window shown below should appear.

2 The wizard starts with an introduction and provides nothing to set so click the Next button. At the first step, we set the PIC microcontroller we will be using the PIC 18F452. Choose PIC18F452 as the Device from the drop-down menu and click Next. The second step of the Project Wizard allows us to choose which toolset we want to use for our project. For the duration of this course we will focus on embedded C programming using the Microchip C18 compiler. Select Microchip C18 Toolsuite for the Active Toolsuite and then click Next. When you arrive at step three, this step allows the user to configure the project name and the location to store it. Since this is the first exercise, Exercise1 should be used as the Project Name. As for the Project Directory, you should browse for the My Documents folder and then click Make New Folder. Name this new folder Exercise1 and select it. Click OK on this directory to use it for our project. Select the Next button to continue on to step four. The fourth step in the wizard allows for existing files to be added to the project. In most of our exercises, we will just skip this step by clicking Next. Click Next to go onto the last step of the Project Wizard. The fifth and final step of the wizard summarizes the parameters set for the project. After examining the information shown, you can click Finish to proceed to create the project. Task 2 - Configuring the device parameters In this task, the linker file is specified and the configuration bits are set for the 18F452 microcontroller. The linker file is a file that the C18 compiler uses to know the memory layout of the microcontroller and the libraries to include for that specific device. To specify the linker script, right click on the Linker Scripts folder. The image below shows where the Linker Scripts folder exists. After right clicking, click Add Files and browse to the C:\MCC18\lkr directory. Finally, select the 18f452.lkr file.

3 After setting the linker script, we will proceed to setting the configuration bits for the device. The configuration bits are device specific parameters related to the device operation. Some examples of these parameters include oscillator type, brown out detection, power up timer, and code protection. To set the configuration bits, select Configure -> Configuration Bits from the menu. Proceed to set the configuration bits to match what is shown in the image below.

4 Task 3 Creating the project s source code For the first exercise of the semester, a basic program is shown that turns the output (pin 19 in this case) on and off. To create the source file, click File -> New from the menus. In the window that is created, type in the following source code: #include "p18cxxx.h" void main(void) //Set RD0 as an output (0=Output, 1=Input) TRISDbits.TRISD0 = 0; while(1) //Set RD0 to a logic 1 PORTDbits.RD0 = 1; //Set RD0 to a logic 0 PORTDbits.RD0 = 0; After you are done typing in the source code, click File->Save As from the menu and save the file to the project directory. Set exercise1.c as the File name. Be sure to check Add File To Project in the dialog before clicking the Save button. Task 4 Building the microcontroller circuit To verify the operation of the code entered, the basic circuit given below should be built. The following elements should be used in the construction: 1. PIC 18F452 microcontroller 2. 4MHz ceramic resonator 3. ICSP pin header 4. 9V battery 5. 9V battery clip 6. 78M05 voltage regulator 7. 10K resistor

5 ICSP Header PIC18F452 Task 5 Compiling the source code and downloading the binary In this last task guided task, we will compile the source code and program the microcontroller. We begin by compiling with clicking Project -> Build All from the menu. Next, we set the programmer and validate the settings. Click Programmer -> Select Programmer -> MPLAB ICD 2 to set the programmer to the ICD2. Now, select Programmer -> Settings and verify that under the Communication tab it has USB selected for the com port. With the settings verified, click Programmer -> Connect to connect to the ICD2 so functions as downloading are possible. If the connection is successful and the proper microcontroller is detected, you will see the following messages in the message window. (NOTE: Be sure to have the power connected to the microcontroller. It is expected that the device is self-powered.) Proceed to program the microcontroller by clicking Programmer -> Program from the menu. Upon completion, to see your circuit operate, you can either disconnect the programmer from the circuit or click Programmer -> Release from Reset. You should now verify the correct operation by using an oscilloscope.

6 Assignment 1. Attach a scope to pin RD0 on the PIC to view the output from the test program. What does this look like? 2. Modify the previous source code to the following: #include "p18cxxx.h" void main(void) //Set RD0 as an output (0=Output, 1=Input) TRISD = 0b ; while(1) //Set RD0 to a logic 1 PORTDbits.RD1 = PORTDbits.RD0; //Set RD0 to a logic 0 PORTDbits.RD2 = ~PORTDbits.RD0; After entering the new code, compile and program the microcontroller. To examine the output attach an LED to the output pins RD1 and RD2 with a current limiting resistor of approximately 10mA. Now, view the output of the circuit when you attach pin RD0 to 5V and then GND. What happens? What happens when you leave pin RD0 floating? 3. Measure the current of the previous circuit. How much current do you measure without the LEDs? 4. Change the 4MHz ceramic resonator to a 20MHz ceramic resonator. This change will also require the oscillator type in the configuration bits to be changed to HS. Erase the device and then reprogram. What type of current does the circuit now consume?