Jon Mayo <jmayo <at> rm-f.net> writes:
> What's the real pin-out of the Gumstix? For example is pin 1 used
> on the Waysmall + Gumstix 400f-bt? is it tied to ground? not connected?
> The reason I ask is because I find a lot of db9 to miniDIN8 adapters in
> my junk bin. Mostly they are wired for Mac rs422 to DB9 rs232. But if I
> can ignore flow control and ignore that they are tying some of the
> unmentioned pins on the Gumstix to ground, then they will work. (I'm
> not willing to plug it into the Gumstix and try it out without having
> an idea of the consequences)
> The Gumstix pinout seems simular to what Sun and a few others uses for
> din 8 on some of its products (not including the sun keyboard/mouse).
> MINIDIN8 Numbers Letters
> _______ _______ _______
> / \ / \ / \
> | O O O | | 8 7 6 | | H G F |
> | O O O | | 5 4 3 | | C D E |
> | O O | | 2 1 | | A B |
> \_______/ \_______/ \_______/
> Sun and other mini DIN-8:
> 1 B CTS
> 2 A DTR
> 3 E RXD
> 4 D Ground
> 5 C TXD
> 6 F RTS
> 7 G DCD
> 8 H NC
> Mac rs422 miniDIN8:
> 1 Handshake-Out (RTS)
> 2 Handshake-In (CTS)
> 3 TX-
> 4 Ground
> 5 RX-
> 6 TX+ (ignore in an rs-422 to rs-232 convertor)
> 7 ??
> 8 RX+ (tie to Ground when doing a rs-422 to rs-232 convertor)
> Gumstix: (according to the Wiki)
> 1 ??
> 2 CTS
> 3 RXD
> 4 Ground
> 5 TXD
> 6 RTS
> 7 ??
> 8 ??
> I suppose I can understand using CTS in place of DTR(if we are
> comparing to what Sun does). Other than that the pins are identical to
> the Macintosh is RS-422 so it has some things like Tx+/Tx- Rx+/Rx- but
> it's not difficult to adapt it to RS-232. As far as I can tell my
> mac->db9 cable doesn't have any funny things like resistors or
> diodes embedded into it, just some pins are coupled together or wired
> to ground. The other interesting thing is RTS/CTS and TX/RX are swapped
> like a null modem cable. (you could almost use a straight-thru cable on
> an old mac to talk to a Gumstix or sun, although I suspect it's not
> quite that easy)
AFAICT, the only gumstix boards that have miniDIN-8 connectors are the tweener,
the console-st, and the console-hw. The ports on the tweener and the console-st
appear to be identical, and perhaps in the next revision of those boards, pin 6
could be wired to pin 4 (ground) _on the board_, which would make them 100%
compatible with all gumstix cables, Apple cables, PCs, and old Macs. The
console-hw boards would necessitate a slight compromise: Since pin 6 is already
used for RTS on those boards, in order to wire it to pin 4 like the other
boards, RTS would have to be moved to pin 1, where it should be. When using a
3-wire serial protocol, this would not affect users of existing gumstix cables.
Of course, this would mean that newly sold gumstix cables would also have to be
wired differently for compatibility with the new console-hw boards. In the new
cables, pin 4 could be wired to pin 8 _in the cable_ for compatibility with
other existing miniDIN-8 equipment; gumstix would be unaffected, since no
gumstix wires pin 8 to anything. I should add that there were many peripherals
that also used the Apple serial spec, many of which still abound in hobbyists'
collections. This could be an additional selling point in the hobbyist market.
Currently, Mac<->PC cables may be used with gumstix for a 3-wire protocol just
fine, but to correctly connect a gumstix, even for a 3-wire protocol, to a
device using the old Apple spec, one must plug a Mac<->PC cable into a
Mac->modem cable. Electrically, the changes would be necessary in order to avoid
this, and they would be so trivial that I don't really understand why this
hasn't already been done. That's my 2¢, and I hope against hope that the
designers take heed. Thank you for your attention.