CAT / RS232 / CW interface (FTDI, MAX232, 5V controllable FETs)

I made a CAT and CW interface from readily available components. Of course it is possible to buy a microham interface or simular. However, I wanted no USB soundcard functionality and Xp, Win 10, Linux compatibility without having to install drivers. A native FTDI chip from SF will do the job nicely. The FTDI chip has 5V TTL out and the true RS232 has +-1 12V signal levels. Therefore I pressed a MAX232 board that I designed approx 10 years ago and was laying in the junkobox into service. 5V TTL into and out from the MAX232 chip into the FTDI chip.
I used some “5V TTL FETs” for switching the CW signal. The RTS / CTS signals from the FTDI interface can drive these fets directly. I needed to invert the signal so that the CW keying is off by default. So since I had two of the 5V TTL FETs laying in the junkbox, I used one to invert and one to drive the CW key output. On the picture to the left the fets can be seen.
Here the quick and dirty prototype can be seen. The old RS232 converter board to the left, the switching FETs to the right and the FTDI board below.

Arduino Based CW keyer / FTDI based CAT interface

I recently needed a new CW keyer with Winkey compatibility for use with my N1MM logging setup. K3NG has written some nice keyer code that I compiled and uploaded to one of my Arduino UNO boards that I had laying in the shack (if you want to try it, you need the latest  – above 1 – version of the Arduino “IDE”). Below you can see some pictures from making the prototype thru to ready made keyer with USB interface and adjustable speed button. I did not install the memory buttons, as I control the CW keyer via USB from N1MM or Hamradio Deluxe. It works very well with my Yaesu FT-450D but instead of the UNO I will eventually use a Mini Pro board with the Atmel Atmega 328. You can see more info on K3NGs site http://radioartisan.wordpress.com/arduino-cw-keyer/#comment-3255

Below is the schematic (remark: full credit is given to to K3NG!). I have modded the design for my own needs. Instead of the 2N2222 I use a TTL tolerant FET of type IRLIZ44N to drive the keyer output. Then I don’t need the 100 ohm resistors in series. I also did connect a piezo tweeter directly to the CPU  without using the 2N222 transistor. It works OK. However, the sound of the piezo tweeter is not the best in the world. Finally, as mentioned above, I did not install all the buttons. I installed only the command button to save space.  There is a need to do a small mod on the UNO hardware due to some reset issues. For that I will have to add another button that needs to be pressed when I want to upload code.

http://radioartisan.files.wordpress.com/2011/03/k3ng-keyer-schematic-2012052101.png

IMG_0789IMG_0795IMG_0806IMG_0801IMG_0811IMG_0815

I also needed a CAT interface. It is possible to use a FTDI chip for this task, however the signal levels need to be transformed to +/- 12V. This I solved with a MAX232 board that I had laying around in the shack. So now I have a CAT interface that is compatible with Win XP, NT, 2000, 98, Windows 7, Windows 8 etc since the FTDI chips are widely supported. It looks like … but works like …

IMG_0772IMG_0777