Peter Feucht wrote:

> This application is nearly what I was looking for, but I cannot see, how the
> needed *negative* voltage for the Tx line is generated. In this application
> the Tx pin of the PIC is simply connected to the Dsub plug resulting in a
> voltage swing of just 0...+5V. But the spec says -5...+5V at least, optimal
> is -12V....+12V.

Most of COM Port in PCs will work from a simple 0-5V voltage... cheap 
mice used to go like that.

-- 
Ciao, Dario
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