>> Is the voltage in rs232 enough to supply vpp?

> AFAIK, a properly implemented RS232 port [...] is supposed
> to deliver at least +/- 12 volts when unloaded.

No.  RS232 specifies that each transmitter output be between
+6V to +25V  or  -6V to -25V.  (The +6 and -6 limits may be
+5 & -5; I don't recall for sure from memory.  Check Motorola
MC1488/1489 or TI 75188/75189 data sheets.)  This tries to
guarantee that the receiver sees +3 to +25 or -3 to -25.

Supplies of +/- 12V used to be common in equipment, so the
serial driver chips used to use those voltages.

                                                Lee Jones

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