Post by thread:Copy of: Re: VERY low cost RS232 PIC Programmer

> is Ok, except the RS-232 readback is really tricky, >> ( CTS is never < -3V what it should be to RS-232 specs) >> but well it seems to work that way too. > >Yes, I know this problem. >The PC's serial port is known for detecting levels below 1 V >as LOW and above 1.25 V as HIGH. > >That's the reason why this circuit works and why it won't on some >of the 'not so compatible' PC's. One solution (as long as we are in clever hacker mode here) on serial ports with "TRUE" RS-232C / V.34 drivers would be to put a fairly large capacitor accross a resistor in series with the serial line. That would cause the data to swing to (up to) +5V on a 0-1 transition and -5 V on a 1-0. On a port with hysteresis, this might work. NB: I haven't tried this, it's just a thought. -Don