So i purchased a new usb to serial adapter for my laptop. The voltages are as 6.11v when on and -5.65V when off for male serial pin 4 when grounded to pin 5. I really do not know how to build a circuit so that the negative voltage is taken to zero and the the new positive voltage will be my high. The only two pin choices I have are pins 4 or 7 grounded to pin 5. These are the DTR and RTS pins. I have been unable to find a RS232 shield has these pin outs passing through the max232 chip. Any advice would be greatly welcomed.
By definition, RS-232 is bi-polar, just like you discovered. Also, by definition, any of the pins can be shorted for ever, without causing problems to the circuit. Therefore (so) I would put a Shotkey diode, capable of 1 amp, on the pin, oriented so a negative voltage is shorted to ground, giving at the most, -0.3 volts.Paul
You were spot on. I have been picking up lots of components from the Radio Shack near my house at 60% off. I had grabbed a 50v-1a Diode. It did the trick. I was able to write a quick Sketch that made the ledPin 13 blink when the serial port hard wired across the diode to PIN 6 was set to high. I think I am all set to go on competing my project. I greatly appreciate all the advice. This has been a great learning experience. By the way after the diode I am getting -.01v to 0vJohn