On Monday 29 Sep 2003 3:20 pm, you wrote: > Ian, > > My PDA works with the 5/0 volt levels. > > I am looking at the 74HCT368 Hex buffer/driver/inverter as the driver. With > it I can switch in/out 2 ports and a couple extra drivers for other things. I have had a look at the data sheet of this and as far as a serial output is concerned I think this will be OK. They will source/sink 6mA with no more than 0.25V drop which impiles thier on resistance is around 40ohms. So they should have no trouble driving 200Pf or so of cable capacitance at 19600 baud. I am not so sure about as a serial input. As you will have seen from other posts on this topic I am in favour of hysteresis on the serial input whcih would normaly mean suigna schmidt trigger device. However, given the relatively short connection length I don't think it will be a problem. Ian > > John > > ----- Original Message ----- > From: "Ian Bell" > To: > Sent: Friday, September 26, 2003 8:55 AM > Subject: Re: [EE:] rs232 line into digital I/O port??? > > > On Friday 26 Sep 2003 4:28 pm, you wrote: > > > > snip > > > > > I can find out, but will not be able to until Monday or Tuesday. > > > > No problem, I am not in a rush ;-) > > > > > > > The length will be 3 feet. 6ft would be great if possible. > > > > > > > > OK, fairly short then, so as a rough guess we can assume 100pF/yd > > cable > > > > > capacitance so design for more than 200pf load. > > > > > > > > > Data rate of 9600 is fine, but of course, higher would be nice. > > > > > > > > 9600 is nice and slow so cable capacitance should not be too much of > > an > > > > issue. > > > > > > > How much higher do you want to go? > > > > > > 14400 would be nice. 19200 would be grand. But 9600 is fine. > > > > OK 19200 is not too high either. we'll take that as the maximum. > > > > Ian > > > > -- > > http://www.piclist.com hint: The PICList is archived three different > > ways. See http://www.piclist.com/#archives for details. > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads