Table of Contents
CED1Z FPGA Project for AD7682 with Nios driver
This document presents the steps to setup an environment for using the EVAL-AD7682EDZ evaluation board together with the EVAL-CED Converter Evaluation and Development (CED) Board and the Nios II Embedded Development Suite (EDS). Below is presented a picture of the EVAL-AD7682 Evaluation Board with the CED1Z board.
The CED1Z board is intended for use in evaluation, demonstration and development of systems using Analog Devices precision converters. It provides the necessary communications between the converter and the PC, programming or controlling the device, transmitting or receiving data over a USB link.
The AD7682 is a 4-channel, 16-bit, charge redistribution successive approximation register (SAR) analog-to-digital converter (ADC) that operates from a single power supply. The AD7682 contains all components for use in a multichannel, low power data acquisition system, including a true 16-bit SAR ADC with no missing codes; an 4-channel, low crosstalk multiplexer that is useful for configuring the inputs as single-ended (with or without ground sense), differential, or bipolar; an internal low drift reference (selectable 2.5 V or 4.096 V) and buffer; a temperature sensor; a selectable one-pole filter; and a sequencer that is useful when channels are continuously scanned in order.
- AD7682 Product Info - pricing, samples, datasheet
The first objective is to ensure that you have all of the items needed and to install the software tools so that you are ready to create and run the evaluation project.
Below is presented the list of required hardware items:
- Analog Devices EVAL-CED Converter Evaluation and Development (CED) Board
- EVAL-AD7682EDZ evaluation board
- Intel Pentium III or compatible Windows PC, running at 866MHz or faster, with a minimum of 512MB of system memory
Below is presented the list of required software tools:
The Quartus II design software and the Nios II EDS is available via the Altera Complete Design Suite DVD or by downloading from the web.
Extract the Lab Files
Create a folder called “ADIEvalBoard” on your PC and extract the ad7682_evalboard.zip archive to this folder. Make sure that there are NO SPACES in the directory path. After extracting the archive the following folders should be present in the ADIEvalBoard folder: EvalBoardFPGA, FPGA, Hdl, NiosCpu, Software and DataCapture .
|EvalBoardFPGA||Contains the reference project which is loaded on the EVAL-AD7682EDZ board. The AD7682.v file contains the main ADC driver modules|
|FPGA|| Contains all the files necessary to program the CED1Z board in order to evaluate the ADC. By executing the script program_fpga.bat the FPGA will be programmed with the evaluation project. New Nios2 applications can be created using the files from this folder.
The ip subfolder contains the HDL core for connecting the evaluation board to the CED1Z board , the software drivers for HAL in /hdl/src/HAL and the AD7682 registers in /hdl/src/inc
|Hdl|| Contains the source files for the AD7682 HDL driver:
- The doc subfolder contains a brief documentation for the core.
- The src subfolder contains the HDL source files.
- The tb folder contains the sources of the core's testbench
|NiosCpu||Contains the CED1Z Quartus evaluation project source files . The ip subfolder contains the AD7682 QSYS component|
|Software||Contains the source files of the Nios2 SBT evaluation project|
|DataCapture||Contains the script files used for data acquisition|
Install the USB-Blaster Device Driver
The USB Blaster is used to program the FPGA on the CED1Z board and also for data exchange between the system and a PC. To install the driver plug the Terasic USB Blaster into one of the PCs USB ports. Your Windows PC will find the new hardware and try to install the driver.
Since Windows cannot locate the driver for the device the automatic installation will fail and the driver has to be installed manually. In the Device Manager right click on the USB-Blaster device and select Update Driver Software.
In the next dialog box select the option Browse my computer for driver software. A new dialog will open where it is possible to point to the driver’s location. Set the location to altera\11.0\quartus\drivers\usb-blaster and press Next.
If Windows presents you with a message that the drivers have not passed Windows Logo testing, please click “Install this driver software anyway”. Upon installation completion a message will be displayed to inform that the installation is finished.
AD7682 Evaluation Project Overview
The evaluation project contains all the source files needed to build a system that can be used to configure the AD7682 and capture data from it. The system consists of a Nios II softcore processor that is implemented in the FPGA found on the CED1Z board and a PC application. The softcore controls the communication with the Device Under Test (DUT) and the data capture process. The captured data is saved into the SRAM of the CED1Z board and aftwerwards it is read by the PC application and saved into a comma separated values (.csv) file that can be used for further data analysis.
CED1Z FPGA Design
The following components are implemented in the FPGA design:
|Table 1 System components|
The Nios II processor contains a peripheral that implements the communication protocol with the DUT. The peripheral is divided into three logical modules: a module which implements the interface with the Avalon bus and the communication with the SRAM, a module which implements an Avalon master interface which is used to write data directly in the SRAM and a module which communicates with the evaluation board. Following is presented a block diagram of the HDL core and a description of the interface signals.
Table 2 describes the port definitions of the Avalon peripheral:
|FPGA_CLK_I||IN||1||System clock. Designed with a 64MHz clock|
|Avalon Slave Interface|
|AVALON_WRITEDATA_I||IN||32||Slave write data bus|
|AVALON_WRITE_I||IN||1||Slave write data request|
|AVALON_READ_I||IN||1||Slave read data request|
|AVALON_ADDRESS_I||IN||2||Slave address bus|
|AVALON_READDATA_O||OUT||32||Slave read data bus|
|Avalon Master Interface|
|AVALON_MASTER_WAITREQUEST||IN||1||Master wait request signal|
|AVALON_MASTER_ADDRESS_O||OUT||32||Master address bus|
|AVALON_MASTER_WRITE_O||OUT||1||Master write signal|
|AVALON_MASTER_BYTEENABLE_O||OUT||4||Master byte enable signals|
|AVALON_MASTER_WRITEDATA_O||OUT||32||Master write data bus|
|BDB_IO||IO||16||Bidirectional data bus used to write/read data to/from the AD7682EDZ board|
|BBUSY_I||IN||1||Signal that indicates the status of the conversion. Once the conversion is complete and the result is available in the output register, the BUSY output goes high|
|BRD_N_O||OUT||1||Signal used by the CED1Z board to read data from the AD7682EDZ board|
|BWR_N_O||OUT||1||Signal used by the CED1Z board to write data to the AD7682EDZ board|
|BADDR_O||OUT||5||Used to select the register to be read from the AD7682EDZ board.|
|BRESET_O||OUT||1||Used to reset the evaluation board|
|Table 2 Port description|
Table 3 describes the registers of the Avalon peripheral:
|CONTROL_REGISTER||0||32||RW|| Bit 0 is used to start data acquisition
Bit 1 is used to initiate software reset of the core
Bit 2 is used to configure the Avalon write master core to write data to the same location
Bit 3 is used to write data to the AD7682 evaluation board
|ACQ_COUNT_REGISTER||1||32||RW||Register used to configure the number of samples to be acquired when acquisition is started|
|BASE_REGISTER||2||32||RW||Register used to configure the base address of the memory location where the acquired data is to be written|
|STATUS||3||32||R|| Bit 0 is used to signal that the acquisition is complete
Bit 1 is used to signal that the internal memory buffer has been overflown
Bit 2 is used to signal that the user has performed a write of a read only register register
|DUT_WRITE_REGISTER||4||32||W||Register used to perform writes on the device under test. Bits [15:0] are used for data and [20:16] are used as address. The rest are discarded|
|Table 3 Register description|
The follwing figure presents the timing diagram for the read operations from the AD7682 driver .
AD7682 Evaluation Board Design
In order to acquire data from the AD7682, several modules are implemented in the evaluation board FPGA.
This module is the actual driver of the AD7682 data acquisition system.
|FPGA_CLK_I||IN||1||20 MHz clock|
|ADC_CLK_I||IN||1||20 MHz clock|
|WR_DATA_N_I||IN||1||Signal used to write data in the driver’s internal registers, data which will be sent to the AD7682|
|DATA_I||IN||16||Data bus, used to send new configuration words to the AD7682|
|DATA_CHANNELS_O||OUT||128||Parallel bus to transfer the data to the CED1Z_interface module|
|DATA_RD_READY_O||OUT||1||Signals that at port DATA_CHANNELS_O there is new data available|
|DATA_WR_READY_O||OUT||1||Signals that the write from CED1Z_interface has been performed|
|MISO_I||IN||1||Signal connected to the SDO pin of the AD7682|
|MOSI_O||OUT||1||Signal connected to the DIN pin of the AD7682|
|SCLK_O||OUT||1||Signal connected to the SCK pin of the AD7682. 20 MHz clock|
|CNV_O||OUT||1||Signal connected to the CNV pin of the AD7682|
|Table 4 Port description for the AD7682 module|
This module is used to communicate with the CED1Z board. It reads the data from the AD7682 module and forwards it to the CED1Z board. It also forwards write requests from the CED1Z board to the AD7682 module, in order to reconfigure the AD7682 acquisition system. In case the acquisition is done on 4 channels, data is mapped at addresses starting from 0x10 (channel 0) to 0x13 (channel 4). In case a single channel is acquired, data is mapped sequentially on each of the eight addresses. In this case, data must be concatenated by the module running on the CED1Z board.
This module is used to generate a 20 MHz clock signal from the 100MHz external clock signal that is available on the evaluation board.
The next sections of this document present all the steps needed to create a fully functional project that can be used for evaluating the operation of the ADI platform. It is possible to skip these steps and load in the FPGA an image that contains a fully functional system that can be used for platform evalution. The first step of the quick evaluation process is to program the FPGA with the image provided in the lab files. Before the image can be loaded the Quartus II Web Edition tool or the Quartus II Programmer must be installed on your computer. To load the FPGA image you must first make sure that the USB cable is not connected to the CED1Z board. Connect the USB Blaster to the J6 connector of the CED1Z and power the board. Run the program_fpga.bat batch file located in the ADIEvalBoard/FPGA folder.
The Evaluation Board design presented on this page is different than the default design loaded on the AD7682EDZ. In order to use the design from this page, the Evaluation Board FPGA must be reprogrammed. To reprogram the FPGA on the Evaluation board, the following steps must be followed, AFTER the CED1Z FPGA has been programmed using program_fpga.bat:
- 1. Connect the USB-Blaster to the P2 port
- 2. Start Quartus II, Start Tools →Programmer
- 3. Select Mode Active Serial Programming
- 4. Press Add File and select EvalBoardAD7682.pof
- 5. Check Program/Configure and Press Start.
- 6. After the programming ends, power off the CED1Z and reprogramm it using program_fpga.bat as described above.
This is a one time operation, as the programming is done on a non volatile memory on the Evaluation Board. In order to restore the original firmware on the Evaluation Board, at step 4 use the configuration file from the CD at Evaluation Board FPGA code/uMUX FPGA CED 2-2/toplevel.pof.
In order to acquire data, follow the instructions in the Evaluation Project Data Acquisition section.
NIOS II Software Design
This section presents the steps for developing a software application that will run on the CED1Z system and will be used for controlling and monitoring the operation of the ADI evaluation board.
Create a new project using the NIOS II Software Build Tools for Eclipse
Launch the Nios II SBT from the Start → All Programs → Altera → Nios II EDS 11.0 → Nios II 11.0 Software Build Tools for Eclipse (SBT).
NOTE: Windows 7 users will need to right-click and select Run as administrator. Another method is to right-click and select Properties and click on the Compatibility tab and select the Run This Program As An Administrator checkbox, which will make this a permanent change.
1. Initialize Eclipse workspace
- When Eclipse first launches, a dialog box appears asking what directory it should use for its workspace. It is useful to have a separate Eclipse workspace associated with each hardware project that is created in SOPC Builder. Browse to the ADIEvalBoard directory and click Make New Folder to create a folder for the software project. Name the new folder “eclipse_workspace”. After selecting the workspace directory, click OK and Eclipse will launch and the workbench will appear in the Nios II perspective.
2. Create a new software project in the SBT
- Select File → New → Nios II Application and BSP from Template.
- Click the Browse button in the SOPC Information File Name dialog box.
- Select the uC.sopcinfo file located in the ADIEvalBoard/FPGA directory.
- Set the name of the Application project to “ADIEvalBoard”.
- Select the Blank Project template under Project template.
- Click the Finish button.
The tool will create two new software project directories. Each Nios II application has 2 project directories in the Eclipse workspace.
- The application software project itself - this where the application lives.
- The second is the Board Support Package (BSP) project associated with the main application software project. This project will build the system library drivers for the specific SOPC system. This project inherits the name from the main software project and appends “_bsp” to that.
Since you chose the blank project template, there are no source files in the application project directory at this time. The BSP contains a directory of software drivers as well as a system.h header file, system initialization source code and other software infrastructure.
Configure the Board Support Package
- Configure the board support package to specify the properties of this software system by using the BSP Editor tool. These properties include what interface should be used for stdio and stderr messages, the memory in which stack and heap should be allocated and whether an operating system or network stack should be included with this BSP.
- Right click on the ADIEvalBoard_bsp project and select Nios II → BSP Editor… from the right-click menu.
The software project provided in this lab does not make use of an operating system. All stdout, stdin and stderr messages will be directed to the jtag_uart.
- Select the Common settings view. In the Common settings view, change the following settings:
- Select the jtag_uart_0 for stdin, stdout and stderr messages. Note that you have more than one choice.
- Select none for the sys_clk_timer and timestamp_timer.
The memory used by the design is should be changed from OnChip ram to SRAM for the .text region.
- Select Linker Script tab.
- Change .text region Linker Region Name from onchip_mem to sram.
- Select File → Save to save the board support package configuration to the settings.bsp file.
- Click the Generate button to update the BSP.
- When the generate has completed, select File → Exit to close the BSP Editor.
Configure BSP Project Build Properties
In addition to the board support package settings configured using the BSP Editor, there are other compilation settings managed by the Eclipse environment such as compiler flags and optimization level.
- Right click on the ADIEvalBoard_bsp software project and select Properties from the right-click menu.
- On the left-hand menu, select Nios II BSP Properties.
- During compilation, the code may have various levels of optimization which is a tradeoff between code size and performance. Change the Optimization level setting to Level 2
- Since our software does not make use of C++, uncheck Support C++.
- Check the Reduced device drivers option
- Check the Small C library option
- Press Apply and OK to regenerate the BSP and close the Properties window.
Add source code to the project
In Windows Explorer locate the project directory which contains a directory called Software. In Windows Explorer select all the files and directories from the Software folder and drag and drop them into the Eclipse software project ADIEvalBoard.
- Select all the files and folders and drag them over the ADIEvalBoard project in the SBT window and drop the files onto the project folder.
- A dialog box will appear to select the desired operation. Select the option Copy files and folders and press OK.
- This should cause the source files to be physically copied into the file system location of the software project directory and register these source files within the Eclipse workspace so that they appear in the Project Explorer file listing.
Configure Application Project Build Properties
Just as you configured the optimization level for the BSP project, you should set the optimization level for the application software project ADIEvalBoard as well.
- Right click on the ADIEvalBoard software project and select Properties from the right-click menu.
- On the left-hand menu, select the Nios II Application Properties tab
- Change the Optimization level setting to Level 2.
- Press Apply and OK to save the changes.
Define Application Include Directories
Application code can be conveniently organized in a directory structure. This section shows how to define these paths in the makefile.
- In the Eclipse environment double click on my_include_paths.in to open the file.
- Click the Ctrl and A keys to select all the text. Click the Ctrl and C keys to copy all the text.
- Double click on Makefile to open the file.
- If you see the message shown here about resources being out of sync, right click on the Makefile and select Refresh.
- Select the line APP_INCLUDE_DIRS :=
- Click the Ctrl and V keys to replace the selected line with the include paths.
- Click the Ctrl and S keys to save the Makefile.
Compile, Download and Run the Software Project
1. Build the Application and BSP Projects
- Right click the ADIEvalBoard_bsp software project and choose Build Project to build the board support package.
- When that build completes, right click the ADIEvalBoard application software project and choose Build Project to build the Nios II application.
These 2 steps will compile and build the associated board support package, then the actual application software project itself. The result of the compilation process will be an Executable and Linked Format (.elf) file for the application, the ADIEvalBoard.elf file.
In case an error appears at compile time with a description like : section .rodata loaded at [00400164,00400477] overlaps section .text loaded at [00400164,004054d7] the enable_alt_load_copy_exceptions option must be unchecked from BSP Editor → Main → Settings → Advanced→ hal.linker
2. Verify the Board Connection
The CED1Z hardware is designed with a System ID peripheral. This peripheral is assigned a unique value based on when the hardware design was last modified in the SOPC Builder tool. SOPC Builder also places this information in the .sopcinfo hardware description file. The BSP is built based on the information in the .sopcinfo file.
- Select the ADIEvalBoard application software project.
- Select Run → Run Configurations…
- Select the Nios II Hardware configuration type.
- Press the New button to create a new configuration.
- Change the configuration name to CED1Z and click Apply.
- On the Target Connection tab, press the Refresh Connections button. You may need to expand the window or scroll to the right to see this button.
- Select the jtag_uart_0 as the Byte Stream Device for stdio.
- Check the Ignore mismatched system ID option.
- Check the Ignore mismatched system timestamp option.
3. Run the Software Project on the Target
To run the software project on the Nios II processor:
- Before running the the software project, the FPGA located on the CED1Z must be programmed with the Nios II system image. To program the FPGA run the ADIEvalBoard/FPGA/program_fpga.bat script.
- Press the Run button in the Run Configurations window. This will re-build the software project to create an up–to-date executable and then download the code into memory on the CED1Z hardware. The debugger resets the Nios II processor, and it executes the downloaded code. Note that the code is verified in memory before it is executed
The code size and start address might be different than the ones displayed in the above screenshot.
Evaluation Project Data Acquisition
After the FPGA is correctly programmed the data acquisition process can start by executing the batch script, called data_capture.bat.
The script by default collects data from a single channel (channel 0) at 250 KSPS. By editing the data_catupre.tcl file, the configuration of the AD7682 can be changed. After changing the tcl script, it is not necessary to reinitialize the system, just rerun the batch script.
If the resulting csv file is opened with Microsoft Excel, the data will be displayed on a single column or on 4 columns in function of the current configuration, with the name of the channel in the first cell.
If the AD7682 is configured to acquire less than 4 channels the remaining channels will have a constant value. For example, in the below picture, a sine signal was applied on the first channel and the rest were left floating. In this case, the first column can be plotted as a sine wave, and the last 3 have a constant value of 0.