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AD7091R Pmod Xilinx FPGA Reference Design

Introduction

The AD7091R is a 12-bit, ultra low power, successive approximation ADC. The AD7091R operates from a single 2.7 V to 5.25 V power supply and is capable of achieving a sampling rate of 1 MSPS. The part contains a wide bandwidth track-and-hold amplifier that can handle input frequencies in excess of 7 MHz. The AD7091R also features an on-chip conversion clock, accurate reference and high-speed serial interface.

HW Platform(s):

System: Microblaze, AXI, UART

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 13.2 (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 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.

Extract the project from the archive file (AD7091R_<board_name>.zip) to the location you desire.

Avnet LX9 MicroBoard Setup

To begin, connect the PmodAD6 to J5 connector of LX9 board, pins 1 to 6 (see image below). You can use an extension cable for ease of use. Connect the USB cables from the PC to the board.

PmodAD6 and LX-9

Digilent Nexys™3 Spartan-6 FPGA Board

To begin, connect the PmodAD6 to JA connector of Nexys™3 board, pins JA1 to JA6 (see image below). You can use an extension cable for ease of use. Connect the USB cables from the PC to the board.

PmodAD6 and Nexys™3

FPGA Configuration

Start IMPACT, and double click “Boundary Scan”. Right click and select Initialize Chain. The program should recognize the Spartan 6 device (see screenshot below). Start a UART terminal and then program the device using the bit file provided in the project *.zip archive, located in the “sw” folder (../ad7091R/sw/AD7091R.bit).

Programming FPGA in IMPACT

If programming was successful, you should be seeing messages appear on the terminal window as shown in the figures below. After programming the AD7091R, the program will display the value of the input voltage. Pressing [Enter] will perform another conversion and display the result.

UART messeges

Using the reference design

Functional Description

The reference design is a custom SPI Interface, containing CS, SCLK, MISO, and a CONVST signal.

The hardware SPI access allows receiving data from the AD7091R.

  • Connecting the PmodAD6 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 or 9600 Baud Rate for the Digilent Nexys™3 Board.
  • Reference voltage is 2.5V

Downloads

More information

resources/fpga/xilinx/pmod/ad7091r.1355151178.txt.gz · Last modified: 10 Dec 2012 15:52 by Alexandru.Tofan