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.
CAT / RS232 / CW interface (FTDI, MAX232, 5V controllable FETs)
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Hi Marius, nice project to play with. I am interested in various CW keying interfaces and would like to experiment with your ideas.
Could you enlighten me with a schematic and some practical writeup on this version.
Cool. One enhancement I work with is to add a wave shaped sidetone unit so I dont have to generate the sidetone on the PC