Notch location on a ribbon connector

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Anyone know if there's a standard approach as to where you should put the notch on a ribbon connector?

For my first revision of boards that interconnect with ribbons, I didn't really think about it and that led to having to keep a drawing of how to make each ribbon cable. I'm sure there's probably a standard of some sort out there but I'm not finding it on google. I can make them all uniform but I'd like to know that I'm making them uniformly correct.

If I use the following diagram where x marks the number one pin,

+-----------+
| o o o o o |
| x o o o o |
+-----------+

Should I put the notch on the north or south side?

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If you use shrouded headers, you can only connec one way. And you assemble all ribbons with the red stripe as pin #1.

Although I often make custom ribbon cables to match odd pin-outs, you basically design your own boards so that all ribbons are one-to-one. Then you assemble them easily with IDC connectors.

David.

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Shrouded headers have the notch on the side where pin 1 is.

Stealing Proteus doesn't make you an engineer.

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And, if you assemble your own cable, say by squeezing the cable and connector in a vise, the banded, red wire side of the cable can actually protrude out over pin one, or over pin 2... So it actually denotes the end of the connector with pin 1, only.

Depending on how the cable was assembled, therefore, instructins in manuals, (eg STK500 or Butterfly, I can't recall which), that say to connect the cable without any twists can be in error.

JC

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Got it. Obviously the red stripe is on the pin 1 side. Makes sense that the notch would be on the pin 1 side too.

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Quote:
Depending on how the cable was assembled, therefore, instructins in manuals, (eg STK500 or Butterfly, I can't recall which), that say to connect the cable without any twists can be in error.

IDC fittings have an arrow for pin #1. You line up the red stripe with the arrow. So I do nt see how you can assemble a cable wrongly.

An STK500 has numbered headers. So you line up your red-stripe with pin #1. If you examine the track side of the header, pin #1 is marked with a square pad.

I would agree that you can twist a ribbon on the STK500 since it does not have shrouded headers. It is not intuitive. But you can always find someone who has twisted the cables.

So you cannot assemble the cable wrong. But you may prefer a left-hand or right-hand cable exit. Especially if space is limited.

David.

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Quote:
So it actually denotes the end of the connector with pin 1, only.

Quote:
But you may prefer a left-hand or right-hand cable exit.

I think we are saying the same thing. The side of the connector with the red wire goes at the end of the connector on the PCB marked #1.

My point was that depending upon how the cable was manufactured, there may be a "twist" in it, (for right or left sided cable exit).

If the PCB connector has a polarized shroud then it is easy, plug it in the way it fits.

Designing your own system? The ISP pinouts are defined by Atmel so that all of the various programmers and development boards can work interchangeably. If you are designing an ISP header you want to follow the standard. If you are routing your own signals via a header you can design the pin out to meet your needs, and the shroud polarity is again at your discretion.

JC

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I am sure that we are saying the same thing. We may use different words.

If your cable is routed to the right-hand side, you want to assemble the cable exit accordingly when you make the IDC connector.

If you are so unfortunate as to be given a left-hand exit cable, you double it over rather than introduce a twist. The strain relief automatically converts a left-hand exit to a right-hand exit.

The simple answer is that fizgig is well-advised to position his shrouded ISP header carefully. And to think about how the IDC cable is actually routed.

David.