427 Class Notes Lab2: Real-Time Clock Lab

Transcription

1 This document will lead you through the steps of creating a new hardware base system that contains the necessary components and connections for the Real-Time Clock Lab. 1. Start up Xilinx Platform Studio (XPS). 2. Create a new project using base system builder. Remember to always create a new directory/folder that will contain all of the files created by XPS. Your dialog box should look something like (the Project File field will reflect your choices): 3. Remove all unnecessary hardware in the following dialog. This includes anything with in the name, Ethernet_lite and the MCB_DDR2. Removing unnecessary hardware options reduces processing time in later steps. Also set the Local Memory Size to 32 KB (just use the corresponding pull-down menu).

2 4.Turn on interrupts for the Push_Buttons_5Bits and the DIP_Switches_8Bits by clicking on the Use Interrupts button that appears when you click on the name of the peripheral (DIP_Switches_8Bits) in the example shown below.

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4 5.Click Finish so the system can generate all of the hardware-related files. 6. Because this system uses interrupts, the system contains an interrupt controller. You can see this if you click on the Ports tab as illustrated in the picture below:

5 7. We need to add a timer for this lab. We will use the Fixed Interval Timer (FIT). It is a simple component that generates a pulse at pre-determined frequency. RIght-click on the DMA and Timer group in the IP Catalog and then click on Add IP: 8.The number of clocks between strobes determines how often the pulses will occur. We want to build a clock so lets pick something that will make it easy for that. I suggest setting the Number of Clocks Between Strobes to 1,000,000. Configured this way, the FIT will generate a single pulse every 1,000,000 clock cycles. Our clock-rate is 100 MHz (set by default) which means that a single clock pulse occurs every 10 ns. 1,000,000 X 10 ns is 10 ms (1/100 second). Later on you will write software that counts 1/100 second events to compute seconds in order to keep time and to perform debouncing of the switches on the ATLYS board. That will be described in the general lab description on the class website.

6 9. Hit OK. 10. We now have a FIT timer but it is not connected to anything. So, let s hook it up. The FIT has 2 inputs (clock and reset) and one output, Interrupt. The function of clock and reset should be obvious. The FIT has a single output, Interrupt, that goes high for a single clock cycle according to how you configured it. In our case, it will go high every millisecond. We can ignore the Reset input but need to connect the Clock input. Click under the Connected Port column and a pull-down menu appears. Select the options as shown below. 11. Click on the Interrupt output (again in the Connected Port column) and the following dialog will appear:

7 This dialog shows what interrupts are currently connected to the interrupt controller. Remember when you clicked the buttons to use interrupts for DIP_Switches and Push_Buttons? That is why they are currently in the list of connected interrupts on the right. 12. Now add the fit_timer_0 (the instance name of the inserted FIT) Interrupt output by selecting it and clicking the top blue arrow to move it over to the list of connected interrupts. It will appear at the bottom of the list with the highest priority. Timer interrupts are generally higher priority than most other interrupts so the default is OK. Hit OK. FIT connections should look as shown below. Note that Rst (reset) is left floating in this case and that is OK. It is OK in this case because we never need to reset the counter (the documentation also states that it is OK to leave the reset unconnected.

8 13. OK, we are now ready to start generating our hardware. You can click Generate Bitstream (the large button near the left of the XPS window) to start the process. This will take a little while because XPS will synthesize a complete system for you that contains a microprocessor, memory and several peripherals. You will see some warning (take a look at them to see if you can make sense out of them) but you should see no errors. 14. Once the process is complete (the last line in the console will say Done!), you will export the design to the SDK. The window below shows what my console window looks like after the process has completed. Export the design by hitting the Export Design

9 button. 15. Export Design brings up the following dialog. Click the Export & Launch SDK button. 16. When the SDK starts up, it presents you with the following dialog:

10 You need to select a workspace. When you do this, it is best to create a new directory that is not contained by the directory that you created for the files generated by the XPS. You can use the Browse button to browse your filesystem and to create a new directory as necessary. I called my directory RealTimeClockExp2Workspace. 17. Create a new Xilinx C Project (see the previous lab for the steps to do this). Select the Hello World project template (again, this was described in previous Lab how-to). Also, remember to regenerate the linker script as was done before. 18. Download and test this system as you did in the previous lab just to check that you did things correctly. It should print out Hello World in the terminal emulator window as the previous lab did. It is probably a good idea to run the Hello World program each time you build a new system. Consider it a simple sanity check. It doesn t guarantee that everything is connected correctly but let s you know that you probably have made any major errors up to this point.

11 Documentation & Source Code You need to read both the hardware and software documentation for the peripherals included in your system. You can view the hardware documentation via XPS and the software documentation via the SDK. In XPS, you simply right-click on the peripheral of interest as shown in the partial screen-shot below: View PDF Datasheet is the option that 4th from the bottom. Click View PDF Datasheet and you will be able to view a PDF document that describes the hardware in detail as shown below:

12 You can view the PDF documents for the other peripherals accordingly. You will be most interested in the microblaze_0_int (interrupt controller), the fit_timer_0, and the Push_Buttons_5Bits (GPIO) peripherals so carefully read their corresponding documentation.

13 The software documentation can be viewed via the SDK. The SDK documentation describes what software routines that you need to invoke to program your peripherals. The partial screen-shot shown below provides two ways to view the documentation of interest. You can click on the Datasheet link for the peripherals of interest or you can click on the documents listed under BSP Documentation (look at the left column, about middle in the screen-shot below). Finally, make sure to review the Xilinx document OS and Libraries Document Collection that was mentioned previously (available from the Xilinx web-site, see the link on the class Documentation page). Look in the Standalone (v.3.03a) section for information on how to enable/disable interrupts on the microblaze processor.

14 I find it most helpful to look directly at all of the source code that is provided by Xilinx. I can usually figure out what I need to know by looking at the source code and reading the hardware documentation. You can find all of the source code in the microblaze_0 directory in the SDK shown in the partial screen-shot below. All of the include files are located in the microblaze_0/include directory. Look in the hello_world_bsp_0 directory for the microblaze_0 directory.

15 The source files are useful as well, located in the libsrc directory as shown below. You can find the source code that is used to access all of the peripherals as shown in the screenshot below.