In SX Microcontrollers, SX/B Compiler and SX-Key Tool, g_daubach wrote:

Hey BPM,

this sounds promising, so why don't you build your own USB-Serial adapter. Knowing the Serial SX-Key input circuitry, you may notice that there is no need for shifting the FTDI chip's signals to +/- 12V.

Regarding ground loops, I absolutely agree with you, as I made my special experience yesterday. On a new SX-based board with an SX-Key USB attached to the usual 4-pin header, I tried to un-solder a capacitor I had added for testing before to a +24 V power line. Unfortunately, my soldering iron was grounded, my PC as well, and the board was still powered when I started this operation.

When I touched the cap's lead with the solder tip, I saw a little spark, and noticed that my 24 V, 8 Amp power supply had switched to fold-back mode, but only after sending at least 8 Amps through the SX-Key USB to the PC to ground to my soldering iron to the cap, etc....

When restoring power, my SX-Key USB got really hot, Totally frustrated, I turned off the whole setup, marked the SX-Key USB as "fried", and had a beer (or two).

Guess what - when I started my work on the setup again today, everything worked as usual, including the "fried" SX-Key. I'm not sure if it has seven lives - at least, it has two :-) .

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