Main Page

Welcome to the main wiki page for CprE 488! See below for relevant information for the weekly labs, and the Project Page for information regarding the course project.

We hope that, as this wiki develops, you will find useful information as you work on the CprE 488 labs. Also, as you discover new tips and tricks, consider contributing as well. Editing is very straightforward - click the "log in" link in the upper right-hand corner and use your usual university ID and password. Please see the MediaWiki page for further details on how to edit.

ZedBoard Tricks and Tips

Auto-loading a design using the sdcard

When jumpers MIO 4 and MIO 5 on the ZedBoard are shorted to 3v3, the board looks for a BOOT.BIN file in the top-level directory of the sdcard. The BOOT.BIN needs to contain the following three files, in this order:

1. A First Stage Boot Loader (FSBL) executable that checks system configuration registers and programs the programmable logic with the appropriate bitfile.
2. A system.bit file created during the conventional XPS build process.
3. An application that will be loaded after the bitfile programming.

Xilinx provides a template for generating the FSBL project. Select "New -> Application Project" in XSDK, name the project zynq_fsbl, and choose the First Stage Bootloader as one of the project template. You should not have to change any of the files in the project, and it will automatically build.

Assuming you then have some other application you would like to load during the boot process, first select that application, then select "Xilinx Tools -> Create Boot Image". This utility should automatically find the three files needed to generate the BOOT.BIN file. Select where you'd like the output files to be generated. Once the .bin file is generated, rename it to BOOT.BIN and copy to your sdcard.

Board Jumpers

If your board is not booting an SD card, you may have an engineering sample board. Check to see if JP6 (just below the top PMOD on the left side of the board) has a jumper connect. The engineering sample boards require this jumper to boot from SD Card.

Furthermore, if you can boot to linux but your usb port doesn't appear to be working, be sure that JP2 is jumped. This provides power to the usb +5v rail.

SDK Tricks and Tips

Matching a BSP to a software project. When an XPS system is exported to SDK, a Board Support Package (BSP) is created that provides drivers for the various peripherals in your design. Any new software projects will be based on this BSP, but on occasion, any existing (or newly imported) projects will still access older BSPs. This is a common cause of missing header files during compilation. To resolve this, right-click on your software project in XSDK, and select "Change Referenced BSP". Selecting the appropriate BSP will update your project to look at the right headers and libraries.

MP-4 Frequently Asked Questions (FAQ)

Q: I would like to record the time between GPS updates so that I can used the in my PID code.

A: For the sake of simplifying, your PID code can assume a constant update rate. Thus your PID will update at a rate of 1. This greatly simplifies the PID code.

Q: Why is the SDK compiler giving errors when I try to use math functions such as atan, pow, sqrt?

A: You need to make sure you have included <math.h>, also you need to link to the math library to your project. Here is a link that talks about this: http://www.zedboard.org/content/problems-fpu-commands-sqrt-atan. Here is the summary: 1) right click on your application project, 2) select the C/C++ Build Settings option, 3) click on the Tool Settings tab, 4)locate the ARM Linux gcc linker-->Libraries pane, 4)add the 'm' library

Q: My quad is ARMing and responding to Bluetooth commands when I have a printf placed in my "send quad commands" loop, but if I remove the printf things stop working.

A: It appears the Zedboard can send commands to the quad faster than it can process. Try placing a usleep(10000) (i.e. about 10ms) in your send loop in order to slow the Zedboard down a little. In other words, make sure there is a delay between sending an "RC channel" message.

Q: I'm sending ARM commands to the Quad, but the Quad is not ARMing (i.e. the red light on the Quad's main board does not come on, which will often start the blades spinning, but not always).

A: There are several possible issues: 1) The channel commands are 2-bytes each, when you write each channel into your communication buffer you need to write the least significant byte first, 2) You should be continuously sending commands to the quad (faster than once per second), if you just send a single ARM command the quad will not respond, 3) Have your Roll, Pitch, AUX1, AUX2, AUX3, AUX4 set to about 1500, this is equivalent to having an RC controller stick dead-center.

Q: For the set RC channel command, the multiWii command wiki says to send 16 uint16_t values, but only shows 8 channels. I'm confused.

A: The multiWii website has a typo. Since you are only sending 8 channels, it should say send 8 uint16_t values.

Q: It's great that the GPS client will send my Zedboad X,Y,Z,Yaw information, but what is the format....

A: When your Zedboard requests GPS information from the client, the client will respond with a 32-byte buffer of data. Each X,Y,Z,Yaw value (in that order) are doubles, thus each is 8-bytes long. To verify you get the byte order correct you will want to send a debug message back to the GPS client that displays the GPS values that you received.

Q: I'm initializing my UART0 correctly with XUartPs_CfgInitialize(), but when I call XUartPS_RecvByte(), I am often receiving garbage data. What am I doing wrong?

A: There are several possible issues at this stage of MP-4. 1) Check that you are initializing your pointer to the XUartPs_Config structure properly using XUartPs_LookupConfig(). 2) Either call XUartPs_SetBaudRate() or XUartPs_EnableUart(). 3) Explicitly reset the TX and RX data paths in the UART0, by setting the appropriate bits in the control register to '1'. This last part is probably a Xilinx bug, since the system reset should also reset the UARTs.

Q: After adding UART0, how can I continue to print out debug messages to PuTTy?

A: Since we are using both of the PS7 UARTs in MP-4, you will need to be careful with regards to what STDIN and STDOUT are pointing to (and serial communication in general). Right-click your application's BSP, and select "Modify BSP Settings". Under the "standalone" option, set both stdin and stdout to point to ps7_uart_1.

Q: How can I determine the Bluetooth MAC address for my quad?

A: You can connect to it using your laptop (if it has Bluetooth) and view the MAC address that way. Or, lookup the corresponding entry in this table:

Quad-ID	Bluetooth MAC
1	81:eb:b6:8b:79:13
2	81:eb:b6:86:e1:d4
3	81:eb:b6:81:b3:6c
4	81:e9:9f:00:f1:a3
5	81:eb:ad:e7:a8:ce
6	81:eb:ad:cd:9a:1e
7	81:eb:b6:90:6a:6d

MP-3 Frequently Asked Questions (FAQ)

Q: How can I speed up the SLOW Linux kernel compile process?

A: Add a -j[number of threads] flag to the command where you compile the kernel. For example, if you want to build the kernel with 16 threads, the command would be "make UIMAGE_LOADADDR=0x8000 uImage -j16". A reasonable rule is to build the kernel with the same number of threads that your computer has cores.

Q: I'm sick of constantly taking out the SD card, copying over my driver, booting Linux back up, and then testing my driver. Is there a better way?

A: Yes, yes there is! You can transfer files to Linux using the XModem protocol. Unfortunately, the version of PuTTY installed on the computers doesn't support XModem. First, download the ExtraPuTTY program: link. Unzip ExtraPuTTY and run the putty.exe program in it. To transfer a file to Linux, first run the rx program in Linux and give it the file name you want your transferred file saved as (rx [filename]). A "C" will be displayed on the terminal. Then, open the "File Transfer" -> "XModem1K" -> "Send" menu on ExtraPuTTY and choose the file you want to transfer. A few seconds later, the file will be transferred!

MP-2 Frequently Asked Questions (FAQ)

Q: I'm having trouble understanding the relationship between the video timing controller(s), video in/out, and the VDMA. What's a good resource to look through?

A: The AXI4-Stream Video IP and System Design Guide provides a very nice overview of how these components work together: ug934_axi_videoIP.pdf

Q: How does converting from RGB to YCbCr work?

A: Some good information on this topic can be found in the datasheets for the RGB2YCrCb and Chroma Resample components found in the MP-2 assignment. Also, take a look at this document for more information about theory of operation ch03.pdf.

Q: What is the starting color sensor for the Bayer pattern we are applying?

A: Look at the datasheets for both the CFA (the hardware module that applies the Bayer filter) and the VITA sensor.

Q: We're seeing multiple compile errors when creating the First Stage Boot Loader (FSBL) design. It's worked all semester long - what gives?

A: The MP-2 FMC-IMAGEON infrastructure only works with an older version of the "standalone" Xilinx library we have been using for our bare-metal software development. That version (3.06.a) is not fully API-compatible with the v14.6 FSBL code. You can either create your own 3.10.a BSP for the FSBL project, or directly fix the compile errors:

• The QSPI library is generating most of the errors, so replace every instance of "XPAR_PS7_QSPI_LINEAR_0_S_AXI_BASEADDR" with "XPAR_PS7_QSPI_FSBL_HACK", or something else that is not currently defined. There are 4 places in the FSBL code to make this change.
• The XDcfg_GetPsVersion() function isn't defined in the 3.06.a standalone BSP. In function GetSiliconVersion(), directly set variable "Silicon_Version" to SILICON_VERSION_3_1, and comment out the call to XDcfg_GetPsVersion().

We will be integrating the camera_app code into the MP-3 FSBL directly, so upgrading the standalone BSP won't work at that point and you'll have to fix the compile errors.

MP-1 Frequently Asked Questions (FAQ)

Q: How do I bind a transmitter to the quad receiver?

A: Follow this YouTube Link [1]

Q: How do I get my changes to my axi_ppm MPD file to be reflected in the XPS project?

A: XPS caches all the pcore metadata when it first launches. Select "Project -> Rescan User Repositories" to see your changes.

Q: What is the MPD file format? How do I add my external signals to the auto-generated IP core?

A: Check out the EDK Platform Specification Reference Manual - the MPD file syntax starts on page 27.

Q: How do I use the logic level converters?

A: See the SparkFun Logic Level Converter Guide to understand the interface. For the cables we use, black/brown is ground, red is high, and other colors are data lines.

Q: My simulation has a "component instance is not bound" error. What does this mean? Why can't I see the signals of my user_logic component?

A: This error occurs because the user_logic file is not in the working library of the simulation and it does not recognize the interface or because the generics and ports of the instantiated component do not EXACTLY match the declaration. To fix this problem you need to include the library of the component you want to use; in this case the library is "axi_ppm_v1_00_a" and the part we want from it is "user_logic". To use this library in your created testbench design, you can take the following 2 lines of code from the top of the file in axi_ppm.vhd:

library axi_ppm_v1_00_a;

use axi_ppm_v1_00_a.user_logic;

MP-0 Frequently Asked Questions (FAQ)

Q: How do I get a 12-bit RGB signal? The settings in axis_vid_out seem to provide separate channels for Red, Blue, and Green, and there's no 4-bit option there.

A: For our purposes, the vid_out doesn't really need any knowledge of the data format, other than it should be taking in the 16-bit signal off the AXI stream and outputting 12-bit pixels. The ug934_axi_videoIP.pdf guide provides a nice overview of the different video out modes, and how you could configure a 12-bit signal.

Q: I'm not seeing anything on my VGA monitor, and I've hooked up everything correctly (as far as I can tell). What should I do next?

A: There are three main points of failure in the design: the v_tc timing controller, the axi_vdma module, and the video out. Connect some internal signals in your design (e.g. the vTIMING_OUT) to a PMOD port so that you can probe them. Keep in mind that the vid_out only will start transmitting when it synchronizes the data coming in on the AXI video stream with the timing data.

Q: I can't see all the signals that are being discussed in the MP-0 document. What gives?

A: Even in the "Ports" tab, XPS hides some connections if they have a default assignment. Click the "Filter" button on the right of the "Ports" tab, and select all the options, including "Default".

Q: What do a correct v_sync and h_sync look like?

A: Check the two links in the prelab portion of MP-0. Your signals, including timing information and pulse polarity, should match exactly what is shown in the digilent datasheet.

Q: I don't understand whether or not I need to connect signal X in component Y.

A: Check the datasheets, either directly in XPS or in the docs/IP/ sub-directory of your MP-0 install. For example, pg044_v_axis_vid_out.pdf provides nice, clear architectural diagrams for the axis_vid_out component. For example, do you need to connect the aclk port to something? Check the diagram on page 8.

Q: This assignment is too hard!

A: Not really a question, but in any case the sentiment is understood. MP-0 is about learning more about the platform and the tools, and it accomplishes that goal. The first design is always the most frustrating, and in MP-0 we wanted to introduce as many Xilinx EDK features as possible, including some of the bugs.

General Software Help

Remote Linux access:

• Download and install NX Client
• Connect to one of the standard remotely accessible Linux machines: ISU Remote Access Servers

Hardware Design Help

VHDL:
Free Range VHDL Reference Guide

Dr. Jones' Practical VHDL Overview (ppt)

Common VHDL Mistakes "Avoiding: My Design Works in Simulation, but not in Hardware!!!" (ppt)

Common VHDL Mistakes (pdf Abbreviated version)

Tools:
EDK User Guide

Quick ISE/Modelsim Overview (ppt) (Note: Was made for an older version of the tools, but should help give you a better understanding of the tools in general)