On Thu, Jan 14, 2016 at 2:38 PM, ultimate quantifier <[email protected]> wrote:
> > > https://onedrive.live.com/redir?resid=9EB0E72EE55E4704!179&authkey=!AAd-Dr9glM_pTj4&ithint=file%2cpdf > > i only did this documentation, someone else figured out the schematic. > that looks exactly like the documentation from the Marty Goodman doc. Does it work okay? I think in that design the resistors are superfluous. The reason is that there's only 110ohms of resistance at the TPDD signal outputs, which is a lot less than 22k, so most of the drop will be across the 22k to ground. If we use the rule-of-thumb for a diode of 0.7V drop at 0V input, you will end up with about -1.8V to the receiver input in the computer. That is low enough to register as a '0'... according to my calcs at the receiver inputs about 0V +/-0.5V swing would be the dead zone. Good idea for using the CDROM audio cables. I was thinking I'd use a pre-molded RS232 cable and a header cut down, and encase the guts in a glob of hot glue at that end for the housing. :)
