Programming Assignment 1: Pushbutton and Light

Transcription

1 CSE 30 WINTER 2010 Programming Assignment 1: Pushbutton and Light Associated Cypress Board: CY3214 Associated Part Family: CY8C24894 PSoC Designer Version: 5.0 Revised: Summary When the push button S1 is pressed, the LED1 is ON. The LED is OFF when the button is released. Setup Open PSoC Designer. Click on File -> New Project. [New Project] window opens. Select Chip-level Project and Type your project name (e.g., P1_PB_Light_C) in the Name box. Click Browse to select the directory where you are storing your Lab assignments. Click the check box to create directory for workspace. Click OK. In the next [Select Project Type] window, select part CY8C LFXI through the View Catalog button and choose to Generate Main file using C. Click OK when done. 1

2 Adding User Module Now add one LED. In the User Module Catalog, expand Misc Digital, Right Click on LED and select Place. Now you should see one user modules added in the Workspace Explorer as LED_1. 2

3 Ports and Pins So now that you have added the hardware you need for this project, you need to connect the hardware to a specific pin to give the microcontroller a way to talk to the LED. Note that a group of 8 pins is called a port. For example, P2[5] is pin5 of port2. Connect the LED to P2[5] (since it has been prewired on CY3214 board, see board to confirm). In the Workspace explorer click on LED_1. Its property window should appear. In the drop down menu next to Port select Port 2. In the drop down menu next to Pin select Port2_5. Also ensure that the Drive is Active Low(the LEDs on this board are active low). Now that you have finished making pin connections for your user module, you still need to make pin connections for your push button. Assign Pushbutton(S1) to Port_1, pin 4 (since it has been prewired on CY3214 board -- see board to confirm). In order to do this double click on Project_name[Pinout] in the Workspace Explorer. In the Pinout diagram that appears, locate Port_1_4 and click on the blue bar. A window should appear that allows you to specify the name and other parameters for this pin. Name this pin PB (to mean PushButton) and change the Drive of this pin to PullDown. PullDown just means that the button will have a 0 value when not pressed and a 1 value when pressed. Click OK in the window to make the change. 3

4 Adding Your Embedded C-code Now that you have the hardware hooked up, you can write a software program to tell the microcontroller what to do. In the Workspace Explorer, Expand the Project_name Folder and Source Files Tab and double click on Main.c. Embedded C-programming tip: Note that Port n register is declared as "Register PRTnDR" So to look at the specific bit in the register of interest, you need to use what is called a mask. The mask for the pushbutton is 0x10 (which in binary is 0001_0000). Notice that the 1 occurs in the bit position 4

5 where S1 is located. ANDing (&) the mask with the PRT1DR register allows us to extract the value of S1 and then store it in a variable, e.g., PB. If the value is 1 the button is pressed. If the value is a 0 the button is not pressed. The size of register PRT1DR (8 bits) also explains why you declared the variable PB as unsigned char (8 bits). Your embedded coding here... #include <m8c.h> // part specific constants and macros #include "PSoCAPI.h" // PSoC API definitions for all User Modules void main() { unsigned char PB; //Push Button(S1) inputs, 0 for not pressed, Positive for pressed while (1) { // detect PB (pull-down) on Port1(PRT1DR) by masking off all bits except the 4th // one (P1[4] remember?) // Refer to Datasheet for LEDs in PSoC Designer to find what API functions to use } // end while } // end main Building and Programming Your Project on PSOC board Now that you have all the hardware and software set up for the program you are ready to build the project and program the board. Select Build-> Generate/Build Project_name Project. This process will compile your code and turn your code into a format(.hex) that your CY3214 will be able to understand. Once you receive a message that your build has succeeded, you are ready to program your board. Connect the MiniProg device to the PC through the USB cable. Attach the MiniProg to ISSP connector(j15) of the board. Make sure Vdd of MiniProg goes to + of ISSP. Select Program- >PSoCProgrammer. This will open the PSoC Programmer. Make sure you have the MiniProg1 port and the appropriate device (CY8C24894) selected. Make sure the appropriate file to be programmed is loaded, by clicking File Load and select Project_name.hex in the Project_name output folder. Make sure the port is connected by clicking Connect next to the Port Selection window. Also make sure the radio button is set to Power Cycle instead of Reset. Now click the Program command. The red light on MiniProg indicates the programming process is working. Hopefully after a few seconds you will see the words Programming Succeeded. Please note that the device family for the CY3214 board is 24x94. To run your program, click on the toggle power button. Wiring and Test Your Design Wire an LED to P2[5]. Wire PB(S1) to P1[4]. Evaluation & Debugging(if necessary) Working? Congratulations! Not working? Go back to the starting point and review each step carefully. 5