logo

CEPD News 
Spring, 2011 - Vol 4, Issue 2

AugBuildingb

Join Our Mailing List!
In This Issue
Society News
IIR Filters continued
Services
Quick Links




Society News
Jason Fritz, PhD, and past chair of the IEEE SPS Denver section will be the presenter for the Signal Processing Society meeting on March 30.  Jason's talk is titled: The Polarimetric Characterization of Precipitation from High Frequency Synthetic Aperture Radar
When: 3/30/2011 06:00PM-07:30PM
Location: Integrated Teaching and Technology Lab (ITLL), Room 1B50, Engineering Drive, Boulder, Colorado United States 80302
Cost: Free
Please see the SPS Events page to register for this meeting and preview other upcoming events:
Calculus Bowl on April 12, 06:00PM
Photo Forensics Fort Collins April 18, 06:30PM
Photo Forensics Westminster April 19, 6:30PM
Why average when you can filter? (part 2)

In our previous newsletter, we presented a digital filter implemented with  floating point math in C. This time we present a filter using fixed point math in VHDL. A code snippet for a first-order IIR filter form is expressed as follows: 

 

PROCESS (resetn, lpfclk) BEGIN
   IF (resetn = '0') THEN
      w1 <= (others => '0');  y     <= (others => '0');
      x  <= (others => '0');  lpfout <= (others => '0');
   ELSIF (lpfclk'EVENT and lpfclk = '1') THEN
      w1 <= w0;       y      <= rightsum(31 DOWNTO 16);
      x  <= lpfin(15 downto 0); lpfout <= slpfout;
   END IF;
END PROCESS;


-- low pass filter --
A1W1 <= a1 * w1; -- use the negative of computed a1 for pos sum
-- make x value Q16 for Q16 addition, sign extend
xQ16 <= X"0000" & x & X"0000" when x(15)='0'
   else X"FFFF" & x & X"0000";  
leftsum <= xQ16 + A1W1; -- leftsum Q16 result
w0 <= leftsum(43 downto 16); 
rightsum <= w0 * b0;  --rightsum Q16 result
slpfout <= y;   -- output

-- low pass filter --

iir1  


Check the code example link later this week for the full VHDL example code. Follow the filter design calculations and frequency response link to determine coefficient values. 

 

Services
 
If you would like help developing a new product or if you find your project understaffed, CEPD can help you meet your deadlines. Our staff draws on years of diverse product design experience to provide creative and timely solutions for your product needs. Some of our specialties include:
  • DSP
  • Embedded Systems Hardware and Software
  • Data Acquisition
  • Wireless Sensor and Telemetry Systems (Zigbee, Cellular, VHF, Bluetooth, ANT+, etc.)
  • Control Systems
  • Programmable Logic: FPGA / CPLD / EPLD
  • Analog Circuit Design
  • Switching Power Supply Design
  • Battery charging (all chemistries)
  • PCB Design and Layout
  • Analysis and Documentation
Our goal is to provide cost effective and expedient design options for our clients. Our services range from an hour of consultation to large turn-key product development projects. We provide detailed proposals, accurate estimates and time schedules to help you manage each phase of the project. We can offer fixed cost or time and materials proposals to suit your specific needs. There is no cost to you for the initial proposal we create and the initial discussion required! 
Sincerely,

The Staff of CEPD, Inc.
2011, CEPD, Inc.             
 303 415-1112    Fax 720 306-4445