Update to Propeller keyer/transmitter

After getting some much needed feedback on my keyer implementation, I have done several revisions to the keyer software, shortly to be posted on gitHub.  Here is the current revision history list.

  Revision History
  ----------------
  Rev 1.1 - Thanks to Eldon, WA0UWH for pointing out a logic flaw in my
            sendData method
  Rev 1.2 - Updated to make into a proper object.  Implemented get/put methods.
  Rev 1.3 - Implemented Iambic A and Iambic B modes and one element memory.
            Made Iambic B mode default
  Rev 1.4 - Added bug mode (dits are automatic, dahs are not)
            Added straight key mode (dit key input keys transmitter manually)
            Added initPins(dit, dah, key, rf) to allow setting of pin assignments.
            Defaults to 0, 1, 2, 27
            Added public method swapPaddles to allow switching dit and dah paddles

I think the keyer is in pretty good shape now.  I welcome any feedback on version 1.4 from anyone that may find it useful.  Reminder that with the addition of proper low pass filters, this code functions as a full fledged CW transmitter for ham radio usage.  Power output is approximately 5-7 mW putting it squarely in the QRP category.  See my previous blog post for a simple amplifier to raise the output power sufficiently for beacon or CW operation.

Keyer / Transmitter bugs found by Eldon, WA0UWH

In my previous post about my Propeller keyer / transmitter, my friend Eldon has been kind enough to point out a logic error that I had in my sendData code.  The effect of the bug would be felt if you attempted to change the pin numbers that the dit and dah paddles were connected to.  Nice catch Eldon!

I have updated the code to fix this error.  At the same time, at Eldon's suggestion, I have also updated the code to make it more of a spin object.  I have added start and stop methods that allow it to run on a separate cog.  I have also made most of the keyer parameters externally readable and writeable by adding get and put methods for each.  For example the frequency can be read or written with getFreq/putFreq.  Have a look at the code for the entire list of get/put functions.  I also renamed the file from keyer.spin to ko7mKeyer.spin in order to try and avoid naming conflicts.

Eldon has implemented a UI in front of this code using a propeller USB prototype board.  Here is his implementation.  Pretty nice, I think.  He can change the frequency and keyer speed through his rotary encoders and display everything on an LCD.  Nice little transmitter, Eldon.

Iambic Keyer / Transmitter update

I have posted a simple update to the keyer / transmitter project on Github.  The change allows you to specify which sideband you wish to use for the transmitter offset.  You specify the frequency the receiver will use and how much you want to offset your transmit frequency.  The idea is to be able to hear your own transmitter in the receiver as a sidetone.  By default I use 600 Hz offset from the receiver frequency.  When I drop down below 30 metres, I typically use lower sideband (LSB) and offset 600 Hz below the receiver frequency and on 30 metres or above, I offset 600 Hz above.  This can now be changed by setting the sideband value to LSB or USB as appropriate.  Previously to achieve the same effect, you would have had to change the toneOffset value to +600 or -600 as appropriate.

Propeller Iambic Keyer or Transmitter

I have put together a simple keyer or CW transmitter using the Parallax Propeller board.  This is sample code that you may find useful for your own experimentation.

To use as a keyer, set Frequency to zero and attach a keyer circuit to the pin defined by keyPin.  I suggest using a 2N7000 or VN10 to drive most modern commercial CW transmitters.  Something like this should be adequate.  The code supports active high or active low keying.

A speaker can be used on RFPin in this mode to allow hearing a sidetone if desired.  By default a 600 Hz tone should be heard.  A two paddle key is attached between ditPin/dahPin and ground.  I use P0, P1 for the paddle, P2 for the keyer output and P27 for RF/Speaker output.  Please change to suit your needs.

To use as a transmitter, set Frequency to the transmit frequency.  A 600 Hz offset is used by default to allow the transmitter to be heard in the receiver as sidetone.  Change the toneFreq constant if you wish to have a different offset.  Change ErrorOffset to correct for any transmit frequency error your propeller may experience.  This tuning to set the ErrorOffset value should only need be done once by zero beating a frequency standard such as WWV.

A low pass filter for the transmit frequency should be connected to RFPin in order to clean up the square wave output sufficiently to meet regulations about signal purity.  I recommend a minimul of a 5 pole filter as described in earlier posts.

Currently only Iambic Mode A is supported.  Future versions will include the ability to set the keyer parameters such as keying speed, character speed, frequency and RF pin assignments as well as changing Iambic modes via the paddles.

Here is a photograph of the current lash-up with my Vibroplex paddles hooked to P0 and P1.

The source code can be obtained from https://github.com/ko7m/Keyer. As always comments and suggestions are solicited.