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.
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:
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.
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|
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.
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.
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 .
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:
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.
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.
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.
The tool will create two new software project directories. Each Nios II application has 2 project directories in the Eclipse workspace.
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.
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.
The memory used by the design is should be changed from OnChip ram to SRAM for the .text region.
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.
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.
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.
Application code can be conveniently organized in a directory structure. This section shows how to define these paths in the makefile.
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
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.
To run the software project on the Nios II processor:
The code size and start address might be different than the ones displayed in the above screenshot.
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.