> > >...it is unlikely that requiring the handshake (if that is > > > the case) is just caused by the hardware: > > > I use the same hardware without any hardware > > > handshake (just 3 wires, GND, TxD, TxD). > > So your particular hardware does not insist on hardware handshaking. > I was the guy that sent a usb-to-serial converter to Olin and I am using > exactly the same converter. So my particular hardware and Olin's > particular hardware are the same! Alas, I dumped my copy of the thread Wouter, so let me apologize for covering old ground. Are you saying that when you use the converter handshaking is required but when Olin used the same converter he did not need handshaking? We've had all kinds of problems with usb-to-serial converters too so I'm quite interested in Olin's observation that there may be different drivers running around. Clearly, either the communications software or the hardware can determine if hardware handshaking is required. My hardware point slips off the thread a bit and goes to the broader question of DCE (modem like) device design. I'm simply saying that it is not unheard of for computer (DTE) RS-232 interface hardware (UARTs) to require handshaking regardless of the communications software using the interface. Two examples of this behavior are the Rockwell R6551AP UART chip and probably the original IBM PC RS-232 adapter card as specified in the legendary "Blue Book." It would seem then that a prudent design of a DCE device should include strapping pins 4&6 on a 9pin (6&20 on a 25pin) to allow even DTE devices that require rudimentary hardware handshaking to send. My apologies if my comments on the broader question caused confusion. Aza D. Oberman -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist