Sunday, 8 December 2013


I mentioned in an earlier post it was my intention that - "eventually - I'll be moving to just an AVR microcontroller on a board with the DDS modules".

Well - it is accomplished...

You see above the new board on the bench, with the familiar tuning knob and display, running my "double DDS RF Generator" code for my multi-band BITX rig.

I've called the new board the R(F)duino for obvious (but still inexcusable) reasons. It uses a simple single-sided PCB...

on which is hosted an ATmega328P and the two DDS modules.

I have set up the system so that it can run the Arduino bootloader and appear to the Arduino IDE as a UNO board, via a serial interface. I've also added an ISP interface, so that more advanced users can program directly from (e.g.) Atmel Studio, via an AVRISP II or a JTAGICE 3 (or any other AVR ISP programmer).

There's also an explicit I2C interface. At the moment, this drives only the LCD display - but I have plans for hanging more sub-systems off the I2C bus.

The programming and I2C interfaces and other features are seen in the following image...

There's lots of I/O, which can be re-configured by programming, but is arranged with my own tuning and control scheme in mind. It also supports some of my ideas for CW, including an iambic keyer.

The system was set up in "Arduino" mode, through the serial port...

I use a USB to serial adapter from 4tronix which has the very considerable advantage that it has been modified for use with "Arduino clones" by the addition of a 0.1uF capacitor from the "modem's" DTR line to the RST pin. Plug 'n play!

All this is going to be (or, at least, lead to) an open-source project, with code and hardware designs available for download (and - perhaps - with hardware available for purchase). It will take a little time so - please - be patient!

For the moment, I'm back to some more experiments operating voice and CW on my new rig with its even newer Digital RF Generation scheme running on the "R(F)duino".

...-.- de m0xpd


  1. Hi, DDS has been available to the QRP user for several years now and also has been available in kit form for several years from several people in the uk, so you are somewhat reinventing the wheel. Would it not have been better to have completed your first article "occams microcontroller" and its use with the sudden instead of just jumping from project to project. Having read your recent article in the SPRAT, I assumed that you wanted to convert QRPer's to this new found technology but your blog is unfinished and this is not the way forward to convert people. You seem to be bouncing from one project to the next and all seem to say the same thing "It will take a little time so - please - be patient!". A better approach would have been to show practical circuits that explain where to connect the dds and what components it replaces (VXO/VFO). Anybody that has played with an Arduino will know about its uses and its purpose in the radio world, anyone who is unfamiliar with the Arduino will just gloss over this as being to difficult and expensive to use. Lets face it, it just replaces a crystal and a few very cheap components. I hope you are not going to continue this with another ten pages of "rich and egotistic text" in the next Sprat

    R Koster G7BHQ

  2. Hi Paul,

    I just wanted to say that I enjoy you blog, and posts like this one very much. It has inspired a fair amount of tinkering on my bench. I think the BITX and these cheaply available DDS modules are a perfect mix for someone who like to tinker with SSB. Showing how easy it is to use with a stand-alone AVR is a nice bonus.

    Keep up the good work,
    Paul - K0EET

  3. Hi Paul,

    Have you noticed how the first people to whine about others' creative output are typically people who produce precious little of value themselves?

    Anyway, I just wanted to let you know that I appreciate that you take the time to document your experiments via your blog. I "discovered" the Arduino just a few months ago, and have learned a great deal from reading your jottings. I look forward to seeing where your creative mind takes you next!

    Mark, AI4BJ

  4. Hi, Paul and Mark AI4BJ, I thought I would put the record straight by responding to (Mark's) comment as I did not want to offend anyone. It would have been nice to have a email address for Paul, then I could have give him my thoughts without going public. I did not "whine" about Paul's circuits or his concept of converting radio ham's from conventional analog circuits to Digital Tuning methods. If you have read the Article in the Autumn 156 edition of the Sprat, you would have noticed that there is no mention of even where to buy this dds module or clear and concise instructions on how to connect it to readers equipment. If you look at another blog entry on here, then you will see that there is reference to the sudden (a CW TX/RX system designed by The Rev George Dobbs G3RJV) The Transmitter has been converted to DDS but there is little about its receiver so is unfinished, Paul suggests that this is the same circuits he used for the SPRAT article, sadly this is not the case. Then a week later Paul goes on to a beacon ? then real time clocks? then GPS and currently an ssb rig (that already has a digital vfo available). If you visit any UK radio rally, you will see homebrewed QRP equipment and most have either a digital readout or some form of digital tuning. For the record, I have been building Radio Equipment since I was lad and have been in the electronics industry for nearly 40 years and have been teaching at college level, the subject for the last 13 years and have taught many students to pass their radio operators exams and have taught many Scouts and Air Cadets. I appreciate anyone who builds electronic equipment and is prepared to share it with others. Our hobby is becoming less popular and we need to promote it and if possible encourage the art of building radio's. It is a sad fact that we live in a world of "ready to run" and to that end home construction will die if we do not do something about it. But we need too educate correctly or we will lose more. On a personal note, I have put together Paul's Arduino based DDS and have used the original display and others that are currently available and can confirm that they do work. I have never favored the arduino as a suitable board for inclusion in a radio project due to its pin out problems and very early on built a standalone veroboard model that is easy to include on any radio build. It is a very simple and cheap task to just program a blank AVR with the bootloader and then just load up the code (much the same way that you would use a PICAXE). I hope this explains matter

    Ray Koster G7BHQ