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

[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!

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moto

[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...

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moto

[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

[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

[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

[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

[motorollin]

Zac67 wrote:
The power pins from the 2.5" plug don't connect to the 3.5" side, so that's not a danger.

Not even if you use the cable the opposite way round to how it was intended and reverse the pinout of the 44 pin side?

Zac67 wrote:
However, how the rest of the signals behave when reversed is beyond me...

Well, I imagine it would be a similar effect to plugging the IDE cable in the wrong way round. I tested the drive in a 3.5" caddy and it worked fine, so at least I didn't kill the drive!

--
moto

[motorollin]

Zac67 wrote:
Well, if you reverse it on the 44 pin side then - yes. Pins 41 & 42 carry +5V, ending up on two data pins (might cause some damage to the I/F, but lower probability), and the GND pins 43 & 44 go to _RESET and GND - no problem. I wouldn't try it, but chances are good you get away with it.  ;-)

The gender changer was on the 44 pin end, so it was that end which was reversed. Looks like I got lucky, since it didn't do any damage.

Phew!

--
moto