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This version (30 Oct 2013 10:05) was approved by Alexandru.Tofan.The Previously approved version (16 Oct 2013 13:27) is available.Diff

AD5628 Pmod Xilinx FPGA Reference Design

Introduction

The AD5628 The AD5628 is a low power, octal, 12 bit, buffered voltage-output DAC. The device operates from a single 2.7 V to 5.5 V supply and is guaranteed monotonic by design. The AD5628 is available in both a 4 mm × 4 mm LFCSP and a 16-lead TSSOP. The AD5628 has an on-chip reference with an internal gain of 2. The AD5628 has a 1.25 V 5 ppm/°C reference, giving a full-scale output range of 2.5 V; the AD5628-2 has a 2.5 V 5 ppm/°C reference, giving a full-scale output range of 5 V. The on-board reference is off at power-up, allowing the use of an external reference. The internal reference is enabled via a software write.

HW Platform(s):

Quick Start Guide

The bit file provided in the project *.zip file combines the FPGA bit file and the SDK elf files. It may be used for a quick check on the system. All you need is the hardware and a PC running a UART terminal and the programmer (IMPACT).

Required Hardware

Required Software

  • Xilinx ISE 14.4 (Programmer (IMPACT) is sufficient for the demo and is available on Webpack).
  • A UART terminal (Tera Term/Hyperterminal), Baud rate 115200 for the Avnet LX-9 Microboard and ZedBoard or 9600 for the Digilent Nexys™3 Board.

Running Demo (SDK) Program

If you are not familiar with LX9 and/or Xilix tools, please visit
http://www.xilinx.com/products/boards-and-kits/AES-S6MB-LX9.htm for details.
If you are not familiar with Nexys™3 and/or Xilix tools, please visit
http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,897&Prod=NEXYS3 for details.
If you are not familiar with ZedBoard and/or Xilix tools, please visit
http://www.em.avnet.com/en-us/design/drc/Pages/Zedboard.aspx for details.

Avnet LX9 MicroBoard Setup

Extract the project from the archive file (AD5628_<board_name>.zip) to the location you desire.

To begin, connect the PmodDA4 to J4 connector of LX9 board, pins 1 to 6 (see image below). You can use an extension cable for ease of use. Connect the USB cable from the PC to the USB-UART female connector of the board for the UART terminal. The board will be programmed through its USB male connector.

PmodDA4 and LX-9

Digilent Nexys™3 Spartan-6 FPGA Board

Extract the project from the archive file (AD5628_<board_name>.zip) to the location you desire.

To begin, connect the PmodDA4 to JB connector of Nexys™3 board, pins JB1 to JB6 (see image below). You can use an extension cable for ease of use. Connect the USB cables from the PC to the board, one for programming (Digilent USB device) and one for the UART terminal (FT232R USB UART).

PmodDA4 and Nexys™3

Avnet ZedBoard

To begin, connect the PmodDA4 to JA1 connector of ZedBoard (see image below). You can use an extension cable for ease of use. Connect the USB cables from the PC to the board, one for programming (Digilent USB device) and one for the UART terminal (FT232R USB UART).

PmodDA4 and ZedBoard

FPGA Configuration for Nexys3 and LX-9 MicroBoard

Start IMPACT, and double click “Boundary Scan”. Right click and select Initialize Chain. The program should recognize the Spartan 6 device (see screenshot below). Connect an oscilloscope to the following outputs of PmodDA4: A,C,E,G. Program the device using the bit file provided in the project *.zip archive, located in the “sw” folder (../ad5628/sw/AD5628.bit).

Programming FPGA in IMPACT

FPGA Configuration for ZedBoard

Run the download.bat script from the ”../bin” folder downloaded from the github (see the links in the download section of the wiki page). The script will automatically configure the ZYNQ SoC and download the *.elf file afterwards.

If the download script fails to run, modify the Xilinx Tools path in download.bat to match your Xilinx Installation path.

If programming was successful, the Main Menu will apear in your UART terminal, as seen in the picture below. There are 3 options:

  • Press [f] to select Fixed Value Mode.
  • Press [w] to select Waveform Generation Mode.
  • Press [p] to select Programmable Ramp Signal Generator.

Main Menu

When entering Fixed Value Mode, DAC selection is automatically activated. Selecting the DAC is done by pressing [1] to [9].

Fixed Value Mode

Fixed Value Mode allows entering a value between 0x000 and 0xFFF, value that will be programmed in the DAC. If the number of input characters is less than 3 (e.g. ff or 76), the [Enter] key must be pressed in order to validate the input. If 3 characters are input, the value is automatically validated (in order to prevent entering more than 3 characters). Pressing the [s] key at any time will enter DAC Selection Mode.

UART messeges

Pressing the [q] key at any time exits the Fixed Value (or Waveform Generation) Mode and displays the Main Menu again.

Returning to Menu

When entering Waveform Generation Mode, DAC selection is automatically activated. Selecting the DAC is done by pressing [1] to [9].

Waveform Generation Mode

Waveform Generation Mode allows selecting between 4 types of waveforms: Square, Triangle, Sawtooth and Sine waveforms. Changing between the 4 is done by pressing [1] to [4] on the keyboard. Pressing [s] at any time will enter DAC Selection Mode. Pressing [q] at any time will return to the Main Menu.

Selecting Waveform type

Programmable Ramp Signal Generator allows generating a programmable ramp signal. This mode can be used to test the PmodDA4 using a Digital Multimeter.

Ramp Signal Generator Menu

Enter time step allows setting a time step between 100 and 5000 ms.

Setting time step

Enter increment size allows selecting an increment size that suits your design. Values can vary from 0x000 to 0xFFF.

Setting step size

Select DAC allows selecting which DAC Output will be used for the Ramp Signal Generation.

Selecting DAC

Run Ramp Signal Generator will start generating the desired output.

Running the Ramp Signal Generator

Using the reference design

Functional Description

The reference design is a simple SPI interface used to communicate with the PmodDA4. The software programs the device sending 12-bit data values read from the keyboard input or from predefined look up tables. The user has the ability to select between two modes: a Fixed Value Mode or a Waveform Generation Mode. Communication between the user and the board is done via UART.


  • Connecting the PmodDA4 to the boards using an extension cable provides ease of use.
  • UART must be set to 115200 Baud Rate for the Avnet LX-9 Microboard and ZedBoard or 9600 Baud Rate for the Digilent Nexys™3 Board.


When using the ZedBoard reference design in order to develop your own software, please make sure that the following options are set in “system_config.h”:

// Select between PS7 or AXI Interface
#define USE_PS7 	 1
// SPI used in the design
#define USE_SPI		 1
// I2C used in the design
#define USE_I2C		 0
// Timer (+interrupts) used in the design
#define USE_TIMER	 1
// External interrupts used in the design
#define USE_EXTERNAL     0
// GPIO used in the design
#define USE_GPIO         0

Downloads

Linux Device Driver

Connect PmodDA4 to the JB1 connector of the ZedBoard (upper row of pins).

Preparing the SD Card

In order to prepare the SD Card for booting Linux on the ZedBoard:

Make sure you have an HDMI monitor connected to the ZedBoard, plug in the SD Card and power on the board. If everything is correct, the system should boot up. If you don't have an HDMI monitor, connect to the board via UART, Baud Rate 115200.

There are 2 ways to test the driver.

  • Using the terminal window
  • Using a serial terminal

Using the terminal window

Open a new terminal window by pressing Ctrl+Alt+T.

Navigate to the location of the device and identify it using the following commands:

cd /sys/bus/iio/devices/
ls
iio:device0 iio:device1 trigger0
cd iio\:device0
cat name
ad5628-1

If the cat name command doesn't return ad5628-1, then change the number of the iio:device, and check again.

cd ..
cd iio\:device1
cat name

To see the list of options that the AD5628 driver provides, type:

ls
dev                          out_voltage4_powerdown_mode
name                         out_voltage4_raw
out_voltage0_powerdown       out_voltage4_scale
out_voltage0_powerdown_mode  out_voltage5_powerdown
out_voltage0_raw             out_voltage5_powerdown_mode
out_voltage0_scale           out_voltage5_raw
out_voltage1_powerdown       out_voltage5_scale
out_voltage1_powerdown_mode  out_voltage6_powerdown
out_voltage1_raw             out_voltage6_powerdown_mode
out_voltage1_scale           out_voltage6_raw
out_voltage2_powerdown       out_voltage6_scale
out_voltage2_powerdown_mode  out_voltage7_powerdown
out_voltage2_raw             out_voltage7_powerdown_mode
out_voltage2_scale           out_voltage7_raw
out_voltage3_powerdown       out_voltage7_scale
out_voltage3_powerdown_mode  out_voltage_powerdown_mode_available
out_voltage3_raw             power
out_voltage3_scale           subsystem
out_voltage4_powerdown       uevent

To set the raw output voltage for channel A, type:

echo 1200 > out_voltage0_raw

To check that the raw output voltage has been set, you can type:

cat out_voltage0_raw
1200

If you want to set the voltage for another channel, replace out_voltage0_raw with, for example, out_voltage1_raw.

AD5628 Set Voltage from Terminal

The commands written above can also be used if not using an HDMI monitor and a wireless keyboard, by using a serial terminal, and typing the commands after the system boot-up is complete.

AD5628 Read Voltage from Serial Terminal

More information