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Digital Signal Processing

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The following downloads and designs are the copyright of Cumbria Designs and are provided free for non commercial use. In return for using any of the material provided below, we ask that you make a donation to a registered humanitarian charity. How much and to which charity is up to you of course. We hope that you find these downloads a useful addition to your projects. 

All programs are offered without warranty and liability against Cumbria Designs for any loss resulting from their use. Unless offered, source code is not available.

Welcome to the DSP section of our website. This is a new field for us so far it it has been a highly rewarding and interesting journey. We're launching this section with a useful Windows program called "FIR Designer". This intuitive little application was developed partly as a learning exercise but mainly because we couldn't find anything similar for free on the internet. The program allows you to design and develop a range of "rectangular" windowed FIR filters for 16 bit DSP processors. Filters include high pass, low pass, bandpass, Hilbert and "Twisted" +/- 45 degree pairs. Two window functions are provided, Blackman and Hamming, which will suit most applications. Graphical output of the impulse and frequency responses are produced along with text listing of the filter coefficients in hex and decimal. Once you are satisfied with a design, the resulting filter kernel file can be saved to a suitable location for editing with a standard text editor such as Notepad or for copying into your application. Three file formats are available; decimal, 16bit hex suitable for processors such as Microchip's dsPIC series and 24 bit hex for the popular ADSP21xx DSP devices. 

FIR Designer is written for Windows operating system and has been tested with Windows XP and Windows 7. To be able to run FIR Designer you will need to download and install Microsoft Net Framework 4. This is a free application and is available for download from here;

http://www.microsoft.com/download/en/details.aspx?id=17851

1. Download FIR Designer from here; FIR Designer either opening the compressed file or saving it to a convenient location.

2. Open the FIR Designer folder and double click on the "setup" file to install.

3. You may be presented with a publisher warning, click OK and the application will install itself and run. 

Please read the help file, which is displayed by pressing the "Help View" button, for instructions on how to use FIR Designer and acknowledgements to those who have contributed to its development. We hope that you find this a useful tool for designing and developing your next DSP project!  

This simple but versatile dsPIC33F based design offers an ideal route into practical DSP. We do not offer this as a full kit but may supply PCBs and short kits in the near future. In the meantime, if you wish to make your own PCB or have a small batch made through a prototyping service, the Eagle brd file is provided below along with the schematic, BOM and overlay. This data is provided for non commercial use only.

Eden dsP PCB board file

Eden dsP Schematic

Eden dsP Topside Component Overlay

Eden dsP Underside Component Overlay

Eden dsP BOM

Eden dsP PCB

Now back in stock! Double sided silk screened PCBs for the Eden DSP module. Price £8.33 + shipping +VAT.

Please use the button below to order securely on-line. Tax and shipping will be applied according to the destination.

Here are a selection of programs written for the Eden DSP Module that may also be easily adapted for other dsPIC platforms. Most of these are "work in progress" and will be updated as development proceeds.

• Flashing LED. A simple way to check that your Eden DSP module is running. Flashing LED

• FIR Filter demonstration. A narrow band 301 tap audio filter sampling at 8kHz. To change the filter simply update the kernel file using FIR designer.  FIR Filter Demo

• DSP IF. Now we're starting to get ambitious! A 13kHz DSP receive SSB/CW IF system with switched bandwidth filtering, de-noiser and auto-notch. (See the Rishworth presentation slides for more details). Note that the AGC system has yet to be implemented. A phase accumulator/look up table routine with interpolation is used to generate the sine and cosine carriers. A more elegant Taylor/McClaurin series based sine generator is on the "to do list" as a replacement for this (see below) . DSP IF Rx

• Sine Wave Generator. The sine wave program uses a polynomial series to efficiently and accurately compute the sine of a 16bit angular representation of phase. In short, it is a small piece of code that can be used to make audio tone generators or to generate the sin/cos carrier signals in DSP IF systems. This demonstration program serves to show how the code is constructed and how it is used. With a little adaptation it could form the basis for an audio signal generator or multi tone source for IMD measurements. In due course I will incorporate this into a revision of the DSP IF to replace the table look up carrier oscillators. Sine Wave Demo  

• Direct Conversion Receiver. This program configures the Eden DSP card to behave as phasing receiver "back end" accepting I and Q audio inputs from a quadrature detector to produce audio out on both channels. The demodulator works in USB or LSB, and a selection of filters are included for speech and CW bandwidths. The program also incorporates an LMS auto-notch and de-noiser. My sincere thanks to Brian George G3ZOH who carried out the testing and assisted development using his Softrock Ensemble II. Two projects folders are presented, one for MPLAB v8.x and the other for use with MPLAB X .

DC Receiver MPLAB v8.x

DC Receiver MPLAB X

The slides used in the presentation to the GQRP Club at Rishworth, entitled "DSP for under £50", can be downloaded from the link below.

DSP for under £50