Also the pin numbering for the tpdd socket is wrong on that drawing. There is a standard for how pins are numbered on plain pin headers and IDC connectors, so, the visual description of which wires go to which pins may be correct, but only consider those pin numbers within that drawing itself. The drawing on the wiki page has the actual pin numbers which is not only according to the standard, but also matches the schematic in the service manual for the drive.
On Mon, Sep 7, 2020 at 8:31 AM Brian White <b.kenyo...@gmail.com> wrote: > That cable diagram doesn't show anything to translate between TTL for the > drive and RS232 for the computer. Maybe it still works by luck but I > wouldn't use it. > > The drive uses TTL voltages that range from 0 to +5v, while RS232 uses > voltages that range from -N to +N, where N is anything from 5 to 15, with a > no-mans-land in the middle from -3v to +3v (which includes 0v) > > So you really want a circuit that converts between the two. The normal > TPDD cable got away with 3 internally biased transistors to do this without > a real max232 chip. It doesn't do the full proper job like a max232 chip, > but it does enough. > > You can build a proper cable using this little pcb and a factory serial > cable with one end cut off, > > http://tandy.wiki/TPDD#Cable > > ...with all the same parts but a few different directions. > > According to > https://worldofspectrum.org/z88forever/tech/hardware.htm > The connector on the z88 is male db9, so, the cable in the BOM already > works for this too, just you'd need to cut off the db25 end instead of > cutting off the de9 end. And you'd have to translate the pin numbers > written on the pcb to the de9 pinpin and the z88's non-standard pinout. I > can add explicit directions for that in a few minutes to remove any > guesswork about that. > > However, I'm confused. This shows a female de9 port? > http://www.larwe.com/museum/z88.html > > Do you in fact have a male or female port on the unit in your hands? > If they actually have female ports, then I'll just make a separate BOM > with a different cable and separate version of the pcb with different > writing on it. > (Even if you don't want to build a cable this way, I still just want the > project to include this for completeness, since there is software to use > the drive on that machine.) > > -- > bkw > > On Sun, Sep 6, 2020, 2:39 PM dano none <daneiche...@hotmail.com> wrote: > >> >> Has anyone tried hooking up a Tandy Portable Disk Drive to a Cambridge >> Z88? >> >> The instructions are here: >> >> http://www.rakewell.com/xob/xob.shtml >> >> I think in the instructions to build a cable is says front of connector, >> I think that means - looking in to the cable from the front. >> >> Anyway, has anyone done this? Looks like the little Tandy Portable lived >> a very exciting life, hooking up with Tandys, Z88's and even knitting >> machines! >> >> <http://www.rakewell.com/xob/xob.shtml> >> Rakewell's Z88 Archive Page <http://www.rakewell.com/xob/xob.shtml> >> 1. Introduction. Disc-88 is a portable, battery-powered disc drive for >> the Z88 computer. It uses readily available 3.5 inch floppy discs as the >> storage medium. >> www.rakewell.com >> >>
