Kanga UK Resources

Here are some resources supporting m0xpd designs available from Kanga-Products UK.

Hardware

DDS Shield
Tx Shield
Rx Shield

Applications

Keyer
VFO
























Arduino DDS Shield

"The m0xpd Arduino DDS shield provides a convenient interface between an AD9850 DDS module and an Arduino, opening up the benefits of this flexible “Electronics prototyping platform”. The shield makes the DDS Module easy to configure (through software) and to control (through familiar, everyday interfaces such as Keypads, Displays and Rotary Encoders)".


To make your shield, download the instructions from here

To understand your shield's hardware, take a look at the schematic...


To test your shield, once it is built, download and run this simple sketch ("sketch" is the Arduino name for a program).

The test program, running on an Arduino with the DDS Shield on top, sets up the system to produce a 1MHz output.

 Your shield should draw around 90mA on the 5V supply from the host Arduino...


There's only one adjustment to make; the trim pot on the DDS module might need adjustment to get the shield's quadrature square wave outputs running.

The square wave outputs are on pins 3 & 4 of the "RF Bus" connector, JP1.

Unfortunately, a manufacturing error on the board has mis-placed the labels for the pins - this is how the labels on the corner of the board SHOULD have looked...


With the test sketch above running, connect a 'scope to the sine wave outputs (on the BNC socket, the JP6 header or pins 1 & 2 of the RF Bus connector, JP1) and confirm the presence of the 1MHz sinewave.

Now look at the square wave outputs (pins 3 & 4 on JP1) and adjust the preset until the 250kHz square waves are running.

What if you don't have a 'scope?

Put a short length of wire (10 cm or so) in the relevant pin of JP1 to act as an antenna. Place a receiver, in SSB mode, close to the wire and tune it to 250kHz (plus/minus an audio offset). You'll soon know if there's a square wave there!







Applications

Iambic Keyer for Arduino

Those new to Arduino will find this application a little more instructive than the usual "push a button and light an LED" example - and it might be useful in the shack!

All my keyers support both a straight key and a paddle - as I find it easier to switch to the straight key to change speed or to send a long "dah" for zero, etc.

This is how you need to hook up the Arduino...



Arduino code for the keyer is available here.

Note that the later "Occam's Microcontroller" rigs have not just integral keyers but also automated CQ calls - you can find the code here.




















Kanga VFO

The m0xpd Arduino VFO system demonstrates use of hardware elements available from Kanga, combining an Arduino (UNO or MEGA), a DDS Module and a display into a system that is both instructive (delving a little deeper into the possibilities of Arduino) and practically useful (you end up with a decent VFO!)...


 

The schematic is shown below...


 

An Eagle schematic file is available here. (Note - there is no board design, nor any intention to produce one)

The Arduino code for the VFO is available here.

Enhanced Kanga VFO 

To coincide with the appearance of the new Kanga / m0xpd DDS Shield, I've put together a second VFO system.


This system is much more advanced than the simpler VFO described above - not just in functionality, but also in hardware...

As well as use of the DDS Shield, the new VFO exploits an I2C interface for the LCD display unit to save on the load on Arduino pins, freeing up some pins to use to support input push-buttons. If you intend to use the display from Kanga UK, you'll find the appropriate software library at this page. If you're using other displays, you must source your own library appropriate to that hardware.

The VFO has three controls; a rotary encoder (with integral push button), used for frequency (and other parameter) inputs and access to the menu system and two push-buttons, used (in normal mode) to change the "speed" of frequency input (the rotary encoder can change frequency in steps of 1, 10, 100 ... 1 MHz) and (in menu mode) to move between the (4) menu categories.

The system supports the amateur bands between 136 kHz and 10m and also offers a continuous "signal generator" mode. There are programmable offsets for each of the five modes (CW, CW(R), AM, LSB and USB) and continuously variable Receive Incremental Tuning (/"Clarifier"). The system can support additive offsets to accommodate an IF stage and has two memories ("VFO A & B"). A hardware input switches between "Receive" and "Transmit" modes.

The system is seen in "Normal" operating mode here...



As you can see, it is made from a stack of Arduino, DDS Shield, Prototyping Shield and an LCD Display (with I2C interface), all of which are available from Kanga UK. Of course, you don't need to use the DDS Shield or the Prototyping board - but it sure makes things simpler! If you're building the VFO into anything more permanent than the experiment described here, you'll certainly want to drop the prototyping shield and mount the rotary encoder, pushbuttons and display into the wall of your enclosure.

In "Normal" operation, the display shows the frequency selected, the mode, the Receive / Transmit status, the RIT offset (above, equal or below the default value for the mode), the VFO selected (A or B) and the band. 

In "Menu" operation, the display format changes - here, for example is the display in Menu 0 (RIT)...



where the RIT value is shown as it is continuously varied. Notice that the "Clarifier" is set above the default 600Hz offset - so the offset status indicator has changed form "=" to "+".

The Arduino code for the enhanced VFO is available here and a schematic of the user interface components is shown below...


[A previous version of this schematic showed the rotary encoder's push-button erroneously connected to A0. Apologies to all those (including Dennis, g6ybc) who were inconvenienced by my mistake.] 

The VFO  is shown above running on an Arduino UNO. It will run on the Arduino MEGA 2560 boards available from Kanga-UK but in this case the display must be connected to the SCK and SDA pins (which are not shared with A4 and A5 on the MEGA).

Kanga VFO 3

A further enhancement of the Kanga VFO code has been produced to support the newly available 20*4 backlit LCD...


The code (which will support both the 20*4 and 16*4 display formats) is available here .











Kanga / m0xpd Receiver Shield

The Kanga / m0xpd Receiver Shield is a simple, Direct Conversion receiver system for the low HF bands...



The Rx Shield uses a 602/612 Gilbert Cell Mixer, followed by a two-stage audio path which supports limited on-board filtering, an off-board send/return loop (in which the user can add volume control, further filtering or processing, etc), on-board Rx muting, and a level control. There is an on-board (LM386) amplifier, which will easily drive low impedance headphones or a speaker.

The structure of the system is shown here...

The "VFO" input is applied at the "Spare" input on the m0xpd RF bus (if used with a Tx Shield and a Kanga / m0xpd RF generator shield, this signal routing will be implemented automatically).

The receiver must be used with a band-pass filter, appropriate to the band of interest. The filter design is shown in the following schematic...



The provision of an off-board loop for the addition of extra processing in the audio path was originally intended to support sophisticated filtering (such as the m0xpd CW filter described in SPRAT 146). However, it can be either ignored (by bypassing with a header jumper, as suggested in the figure above) or it can be used to provide a convenient volume control. The “gain” control on the shield is only a small trimmer and the shield may not be positioned to allow easy access to this trimmer in use – so a real “volume control” is better for operation.

The external loop must preserve the dc “biasing” of the audio signal in order to the Rx mute to work, so a simple way to implement a volume control is suggested in the figure below, in which a potentiometer, configured as an ordinary potential divider, is grounded not to “ground” but to an “ac ground”, provided by a large capacitor.

The shield's audio path has been provided with limited on-board filtering, to give frequency response as shown...


Rx muting is achieved by pulling the Rx mute line to ground - this is usually connected to Arduino pin D10 (which is used for this purpose in the "Occam's" software).

This receiver developed from an ancestor within the Occam's Microcontroller project - you will find the code developed for that project here.












Kanga / m0xpd Transmitter Shield

The Kanga / m0xpd Transmitter Shield is a simple, Direct Conversion transmitter system for the low HF bands, based on grjv's "Sudden"...
The transmitter was originally developed to operate CW (and can easily form a complete CW transceiver system with an Arduino, an RF Generator board, such as the DDS Shield and an Rx Shield). However, it has also been used as a beacon transmitter in various other beacon and digital modes and as a DSB transmitter.

It will generate approximately 1.5W on the low HF bands.

The shield includes an RF buffer / driver circuit to feed the VFO signal to the Rx Shield, a keying stage and a 5V power regulator, in addition to the RF power amplifier (although use of the 5V power regulator is recommended only to power a DDS Module, rather than an Arduino).

You must use the transmitter with an appropriate output filter - appropriate designs can be found on the G-QRP website.

As with the receiver shield, this transmitter is related to the Occam's Microcontroller project - you will find the code developed for that project here.

12 comments:

  1. I have complete set of parts and boards from Kanga, build dds shield and wired up display using I2C as in your notes. Clicked on sketch link and went to GIST site, downloaded and untazed the file but there is no extension on file. I then copied text from file and pasted in programmer got lots of errors
    This report would have more information with
    "Show verbose output during compilation"
    enabled in File > Preferences.
    Arduino: 1.0.5-r2 (Windows NT (unknown)), Board: "Arduino Uno"
    sketch_feb25a:159: error: 'LiquidCrystal_I2C' does not name a type
    sketch_feb25a.ino: In function 'void setup()':
    sketch_feb25a:165: error: 'lcd' was not declared in this scope
    sketch_feb25a.ino: In function 'void LCD_Display_Freq(double)':
    sketch_feb25a:395: error: 'lcd' was not declared in this scope
    sketch_feb25a.ino: In function 'void LCD_Display_RiT(int)':
    sketch_feb25a:410: error: 'lcd' was not declared in this scope
    sketch_feb25a.ino: In function 'void LCD_Clear_RiT()':
    sketch_feb25a:417: error: 'lcd' was not declared in this scope
    sketch_feb25a.ino: In function 'void LCD_String_Display(int, int, char*)':
    sketch_feb25a:423: error: 'lcd' was not declared in this scope
    sketch_feb25a.ino: In function 'void LCD_Int_Display(int, int, int)':
    sketch_feb25a:428: error: 'lcd' was not declared in this scope
    sketch_feb25a.ino: In function 'void LCD_Char_Display(int, int, char)':
    sketch_feb25a:433: error: 'lcd' was not declared in this scope
    sketch_feb25a.ino: In function 'void setTxDisplay()':
    sketch_feb25a:473: error: 'lcd' was not declared in this scope

    ReplyDelete
    Replies
    1. Tim
      It sounds as if you either a) do not have the correct LCD library installed (there is a copy of it on the Occam's Microcontroller Software page: https://sites.google.com/site/occamsmicrocontroller/home/software )
      or b) there is some problem with the installation of that library on your system.

      Delete
  2. I had similar errors before installing the LiquidCrystal_I2C library but all ok after installation. .... Except that the display reads 'MHzz' after the value [Cont mode] unless I'm on 10.000000 in which case it moves right and reads 'MHz' ...... then 9.999999 moves left and reads MHzz again. I'm trying to spot a fix but you may already have done this? Nice application BTW.

    ReplyDelete
    Replies
    1. Richard
      Sorry - hadn't spotted this. Can you try adding a space after MHz (inside the inverted commas) in the function call to lcd.print in LCD_Display_Freq() (the first of the subroutines - easy to find). Like this: lcd.print(" MHz ");

      Let me know if it works.

      Delete
  3. That seems ok. Still does the shift right-left but does maintain 'MHz'. Thank you.

    ReplyDelete
    Replies
    1. Great - can you tell me which program we're talking about - and from where you downloaded it.
      I'll fix the source.

      Delete
  4. I'll keep a closer eye on this comment .... not sure the previous one got there.

    Can I alter the values 4294967295/125000000 to shift the frequency slightly? I guess that the first part is the maximum division ratio and the second value the TCO frequency?

    ReplyDelete
  5. Ok ... previous comment didn't go properly. It said that the code came from the link on this page to GitHub Gist m0xpd / Kanga VFO 2 [see line 400].

    Also, similar extra z or zz when RIT reduced .... not a big issue.

    Also seem to be 0.001% low in frequency compared to my frequency counters .... which may need checking!!

    ReplyDelete
    Replies
    1. Richard
      Please can you contact me by email (see QRZ.com).
      We'll deal with this outside the "comment" framework and then share outcomes publicly.

      Delete
  6. OK ... last comment .... guess my TCO is running a bit slow .... changed 125000000 to 124998750 to get the o/p frequency in line with my counters. Off-air standard for me next then ??

    ReplyDelete
  7. hello dear friend i am 9a3xz .what things are included arduino dds shield m0xpd from Kanga - uk ?

    thanks in advance

    ReplyDelete
    Replies
    1. Mikele
      I can't speak for Kanga - you should check out the shield directly on their website (the address is: http://www.kanga-products.co.uk/index.php?option=com_content&view=article&id=88&Itemid=99).

      However - unofficially - I know that their kit includes all the hardware (including the DDS module and all the connectors) you need to complete the shield.

      Delete