2.5" to 3.5" IDE adapter cable the wrong way round?

[motorollin]

The answer to this question might be obvious, but I'm going to ask it anyway just to check my own thinking. After all, I don't want to blow anything up.

This cable is designed to connect a 2.5" IDE device to a 3.5" interface. But I want to use it the other way round. I want to connect a 3.5" drive (a full desktop CD-ROM) to a 2.5" interface (the IDE interface inside a small USB hard drive).

Obviously I know I will have to connect power to the drive separately and ignore the power connectors on the cable (better cut them off to be safe...) and I know the gender of the 44 pin connector will be wrong, but I have a 44 pin gender changer to sort that.

So, am I correct in thinking that this will work?

--
moto

[Jeff]

Keeping the fact in mind that power is sent over the last 4 pins of the 2.5 inch IDE connector, the data transfer portion (pins 1-40) will work either way.

I have an adapter cable that I made up that looks just like yours and it works great both ways.

-Jeff

[motorollin]

Jeff wrote:
Keeping the fact in mind that power is sent over the last 4 pins of the 2.5 inch IDE connector, the data transfer portion (pins 1-40) will work either way.

I thought as much, but I wasn't sure whether the pins on these cables were connected straight through or whether there was some difference between the pinouts of each drive type meaning that the cable would only work one way. Thanks for confirming that it works!

Jeff wrote:
I have an adapter cable that I made up that looks just like yours and it works great both ways.

It's good to get this info from someone who has actually tested it ;-)

Cheers!

--
moto

[adolescent]

The gender isn't wrong.  Cables for 40 and 44 pin IDE are both female, and the controller/devices are both male.

If you're thinking of extending a cable with the gender changer then it won't work.  (As explained to me on EAB) when you use a simple pin header to extend a cable you end up inverting the top and bottom rows of the cable.

[motorollin]

The cable is female, and the interface is female. Trust me, I'm looking at it right now :-) I didn't know about the pins being inverted. That would explain why it didn't work...

--
moto

[Zac67]

The adapter is of a simple mechanical / electrical type and will work either way, provided you connect it correctly (i.e. the 4 power pins from the 2.5" side lead nowhere) and the device is compatible. I've built adapters like this many years ago - reconnecting a standard 2,5" cable to a 3.5" connector - and they all worked.

[motorollin]

The gender changer wasn't a cable BTW, it was one of these:

http://www.solentcables.co.uk/acatalog/AD-144.jpg

So I don't see why it would reverse the rows of pins. It didn't work anyway, but the IDE to USB adapter was some really cheap and nasty one so I suspect it only works with hard drives and not ATAPI devices.

--
moto

[Zac67]

A straight-through gender changer reverses pin order! (or rather: chances are high)

Dunno why you actually need something like that since all IDE devices are male... If you're just using a standard 40 pin cable as extension: you ARE reversing pin order. Just check with a simple multimeter.

IDE hard drives and ATAPI devices have the exact same physical interface - however, some USB adapters work only with one kind (ATAPI is more like 'SCSI over IDE').

As a pretty simple solution to your problem: get a halfway decent USB-to-IDE adapter and off you go.  ;-)

[motorollin]

Zac67 wrote:
A straight-through gender changer reverses pin order! (or rather: chances are high)

I can't get my head around how that is possible, but I'll take your word for it.

Zac67 wrote:
Dunno why you actually need something like that since all IDE devices are male...

The drives are all male. So the interface is female. The cable I have is female both ends. One female end connects to the male drive. So the other female end needs to go to the interface, which is also female. That's why I need the gender changer.

Zac67 wrote:
IDE hard drives and ATAPI devices have the exact same physical interface - however, some USB adapters work only with one kind (ATAPI is more like 'SCSI over IDE').

I think I'm just going to get one of these.

--
moto

[rkauer]

motorollin wrote:
The gender changer wasn't a cable BTW, it was one of these:

http://www.solentcables.co.uk/acatalog/AD-144.jpg

So I don't see why it would reverse the rows of pins. --zip--
moto

 That row of pins is the problem.

 It inverts the pins of the connector. So 1 become 2, 3>4, 5>6...

 You need to dessolder the 44pin connector and solder that pins instead (carefully to not blow anything).

[Zac67]

motorollin wrote:

Zac67 wrote:
A straight-through gender changer reverses pin order! (or rather: chances are high)

I can't get my head around how that is possible, but I'll take your word for it.

Just imagine using two 40 pin cables, one extending the other. Their middle connection is that gender changer of yours. You have two options for connecting them:
either the small coding studs face the same way - oops, look at the colored conductors for pin 1: you're connecting 1-39, 2-40, 3-37, ...
or you match the colored conductors to the same side - oops, now your connecting upside down (studs on opposite sides): 1-2, 3-4, ...

Zac67 wrote:
Dunno why you actually need something like that since all IDE devices are male...

The drives are all male. So the interface is female. The cable I have is female both ends. One female end connects to the male drive. So the other female end needs to go to the interface, which is also female. That's why I need the gender changer.

I see - it's an adapter for connecting a 2.5" directly, w/o cable.

 ;-)

[motorollin]

Zac67 wrote:
Just imagine using two 40 pin cables, one extending the other. Their middle connection is that gender changer of yours. You have two options for connecting them:
either the small coding studs face the same way - oops, look at the colored conductors for pin 1: you're connecting 1-39, 2-40, 3-37, ...
or you match the colored conductors to the same side - oops, now your connecting upside down (studs on opposite sides): 1-2, 3-4, ...

Hmm, I think I understand. I still get confused soldering straight through cables like serial cables, as I can't get my head around whether to go pin # -> pin # or whether to make the plugs mirror images of each other, or whether to make the plugs identical to each other... for some reason my occipital lobe is incapable of manipulating cables :-)

I've just had a scary thought. Since one end is a 44 way connector, does this reversing of pins mean that one of the power lines has been connected to one of the data lines in the CD-ROM? Would that damage it?

Zac67 wrote:
I see - it's an adapter for connecting a 2.5" directly, w/o cable.

Yes, exactly. It is designed to connect a laptop drive directly to a 3.5" header on a motherboard.

--
moto

[adolescent]

@moto

I had the same question.  It was explained, and I did a little experiment to understand why.  

Take two bits of paper and draw a female connector on each and number the end pins (1,2,43,44).  Now, get those two female connectors to line up correctly. :-D

To answer your other question, yes you can blow stuff up if you hook the cable up wrong.  I blew out a buffered IDEfix adapter hooking it up wrong on my A1200.

[Zac67]

The power pins from the 2.5" plug don't connect to the 3.5" side, so that's not a danger. However, how the rest of the signals behave when reversed is beyond me...

[motorollin]

adolescent wrote:
Take two bits of paper and draw a female connector on each and number the end pins (1,2,43,44).  Now, get those two female connectors to line up correctly. :-D

I couldn't do it on paper... but I got two female cables and put one against the other and proved to myself that the pins get reversed :-)

--
moto