Serial cable for Phoenix interfaces

[gw1]

Another trap for those buying a serial cable is to make sure it's FULLY WIRED. A proper serial extension cable will have DB9 male on one end, DB9 female on the other, with pin 1 joined to pin 1, pin 2 to pin 2 etc for all nine pins.

I had the misfortune recently of being reminded that there are cheap ones out there which only contain four wires instead of nine. I spent ages trying to get a friend's setup to work, suspecting a faulty serial card or interface, until I noticed that the software sprang to life when I unplugged the cable, indicating that something was up with the hardware handshaking lines.

Crappy four-wire cables will typically be thinner in appearance than the fully wired ones, and significantly cheaper too, but the difference isn't always obvious. Four-wire ones have loopback connections between some of the hardware handshaking pins at each end. For some communication applications you can get away with that, but not all. The Phoenix interface hardware requires not just RXD and TXD signals but RTS too. And depending on what software you're using you'll probably require CD, and other signals like CTS, DSR or RI may also be monitored (though ideally they shouldn't be).

If you find a four-wire cable in your junk box then the best thing to do is to cut it in half and put it in the bin. That might save you hours of frustration down the track.

Finally, don't confuse serial extension cables with null modem cables. A null modem cable has female connectors on each end and several pairs of wires swapped over. It's very different to a serial extension cable.

NULL MODEM CABLE + GENDER CHANGER does not equal SERIAL EXTENSION CABLE

Use your null modem cable for updating the firmware of your set top box, not for Phoenix or Logger interfaces.

[beer4life]

Perhaps this will help with explanation.
Kindest Regards, " The Druid ".

[sublib25]

PARALLEL serial leads here guys, for phoenix use.
Full serial leads have no probs on most pc based apps,
Someone at the bus stop told me that DM's run fine with out pins 1 , 6 & 9
connected in a parallel cable but, can have hastles if all connected.
Never did explain to me why.
STILL CURIOUS - In the words of a IPSWICH imortal - PLEASE EXPLAIN??????

[beer4life]

PARALLEL serial leads here guys, for phoenix use.
Full serial leads have no probs on most pc based apps,
Someone at the bus stop told me that DM's run fine with out pins 1 , 6 & 9
connected in a parallel cable but, can have hastles if all connected.
Never did explain to me why.
STILL CURIOUS - In the words of a IPSWICH imortal - PLEASE EXPLAIN??????

G'Day Cobber,
I thought if I waited long enough, that " gw1 " would be better able to give you a comprehensive answer.
Nevertheless I think this will give you something to chew over instead of what someone at the bus stop said.
Kindest Regards, " The Druid ". .......

[gw1]

I haven't looked at the source for the DM phoenix driver so I can't be certain, which is why I didn't comment

But if you've had problems using DM with a phoenix interface then my guess would be your interface is generating the wrong polarity for CD on pin 1. Another possibility is that the firmware is expecting particular handshaking on pin 6 (DSR), though that's much less likely because DSR has never been required for Phoenix protocol.

There's also a possibility the DM firmware has left its UART's hardware handshaking turned on, which can lead to grief with either DSR or even CTS (pin 8). It wouldn't surprise me. I get the impression the DM guys never paid a lot of attention to their device drivers otherwise they would have fixed the DM500's internal card slot.

@sublib25: I know what you mean when you refer to your cable as a "parallel serial lead" but IMO it's preferable to call them something else - anything else! Saying "parallel" leaves half your readership confused with LPT port and DB25 / Centronics printer cable. Saying "parallel serial" may cause newbies' heads to explode

[sublib25]

Thanks for the reply's appreciated, In all honestly I'm more interested In WHY it works not just that it does.
I litterally know sweet F A when it comes to to pc comms but from reading I had assumed it had something to do with hand shaking protocal as GW1
suggested.
I just thought those that had more hair to rescue than myself may appreciate a bit of help before the pulling began.