differences between passive and active logging cables

[66gsx]

I'm in the process of setting up my datalogger and have been doing alot of searching on the subject of cables. I believe I have a clear understanding of the basic cable and what it entails with the resister and the diode, I'll be building it this weekend.

Where I start to get a little confused is with the cables I've seen with the active circiutry built into them.

Most of the information, and also the schematic I'll be using to build my cable, has been posted by steve. It has all been very very helpful, but I noticed steve mention that the passive cable might be less reliable as far as what it's putting out as compared to the active circiut cable.

I'm somewhat under the impression that this is more the case with a laptop than it is with a palm, but I'm just guessing. If steve or anyone else in the know would have any information on this I'd love to hear it, and I'm sure others would as well as there seems to be a little confusion on this subject.

FYI... I'll be using mmcd software on a palmIIIxe running 3.5.3 o.s. to log on a '93 gsx

thanks, mark

 

[steve]

I haven't been ignoring you, I just don't know what more to say on the subject.
Pasive cables work only because and when the computers serial port is forgiving does most of the conversion in signal levels from the ECU. What the diode and resistor produce isn't RS-232 by any stretch of the imagination. The various active circuits like the one on the MMCd page use a real RS-232 level converter.

On most palms this really isn't an issue but people get cheap cables or plug in other devices and sometime the tricks that make the passive cable work don't anymore.

Steve